Gold Electrolysis Machine

— Gold Electrolysis Machine: Modular Units Rated to 99.99% Gold

A gold electrolysis machine is a self-contained refining unit that hangs a cast crude-gold anode in a heated chloride electrolyte, drives it with a direct current that carries a superimposed alternating component, and plates fine gold onto a seeded cathode — then washes, dries, melts and assays that deposit to a released ingot assaying 99.99% and above. YuSai Machinery builds it as one machine rather than a list of parts: cell and electrode assemblies on a common frame, rectifier and AC-DC superposition unit in an isolated cabinet, electrolyte make-up, circulation, dosing and temperature control, sealed headspace with condenser and scrubber, the harvest and casting station, and the PLC that holds the cycle and records it.

The rated output, the space it needs and the services it draws are engineered to your anode assay and target daily output and stated in the process design package before manufacture begins.Product: Gold purity ≥ 99.99%.

Product Overview

A gold electrolysis machine is a production unit built around one electrochemical cell or a small bank of them, and its purpose is to take metal that is already metallic and make it purer. That single sentence separates it from the two machines it is most often confused with. A gold electrowinning circuit has no anode to dissolve: the gold is already in solution, in an eluate, a strip liquor or a plating rinse, and it is recovered from a liquor rather than purified from a plate. A hydrometallurgical refining plant goes further upstream still, dissolving and separating material that is not yet metal at all. This machine sits downstream of both, at the point where gold has been reduced, dried and cast into an anode plate, and its whole design is organised around keeping that plate dissolving.

The unit is delivered as a machine, not as a collection of vessels. The frame carries the cell and the electrode assemblies; the rectifier and its superposition unit sit in their own compartment, separated from the acid vapour that fills a gold refining room because that vapour is what decides how long a power supply lasts; the electrolyte circuit — make-up vessel, circulation pump, filtration, level dosing, temperature loop and bleed — is mounted as one train; the sealed headspace is ducted through a condenser to a scrubber; and the harvest station, drying oven, melting furnace, sampling bench and records sit at the discharge end. The control panel holds the cycle together and logs it. Everything that touches electrolyte is specified for hot chloride duty, and everything that could be opened by an operator during a campaign is designed to be watched through instead.

The most consequential decision on this page is what the machine’s rating means, because it is the number every buyer compares and almost nobody defines. A rated output quoted as fine gold deposited is the refined product weighed off the cathode after washing and drying — the metal the customer sells. A feed figure counts the crude gold that went in, including the silver and copper that leave as slime and as electrolyte, so a machine rated that way looks larger for the same output. An anode-consumption figure counts metal that partly returns to the melt as residual plate. The three can differ by a third on the same cell. This machine is rated on fine gold deposited, and the basis is written into the process design package so that a quotation can be audited rather than trusted.

What sets the size of the machine for a given job is not a model number but the composition of the anode and the output the plant intends to sell. The gold content of the anode fixes how much metal has to be dissolved to produce a given deposit. The silver content fixes how hard the anode can be driven before silver chloride film starves the dissolution reaction, which in turn fixes the cathode area needed to hit the target in a working day. The copper content decides how quickly the electrolyte loads up and therefore how often the circuit is bled. The target daily output and the number of shifts decide the cell count and the harvest rhythm. Two customers with the same monthly tonnage but different silver loads will therefore be sold machines of different cathode area, and the difference is arithmetic rather than salesmanship.

The machine’s operating cycle is the organising idea of the whole unit. A lot is registered and the machine is checked against its configuration; the anode is cast, bagged and hung; the electrolyte is charged and its gold tenor verified; the power is ramped on a staged programme that builds a coherent seed deposit before full current is applied; deposition runs supervised, with the panel watching voltage, current and busbar temperature and the operator pulling the anode for inspection on the schedule the silver load dictates; the cathode is drawn, washed and the wash water returned to the circuit rather than sewered; the gold is dried, weighed and reconciled against the ampere-hours passed; the slime is drawn, the filter changed and the electrolyte topped up and bled on the assay; and the batch closes with a cast, sampled, assayed ingot and a machine reset for the next lot. Nine stages, one operator, one record per lot.

The machine also has limits, and they are stated here rather than discovered after purchase. An anode above the working silver ceiling will passivate before it dissolves, so the material has to be parted first — with nitric acid where the gold-to-silver ratio allows it, or through the silver circuit where the silver is the larger value. A low-grade ore or an un-stripped electronic scrap stream is not a feed for this machine at all, because the dissolution reaction and the plate integrity both depend on the anode being mostly gold. And below a certain daily output the machine cannot carry its own working inventory, its supervision and its floor space, in which case the honest answer is a toll-refining arrangement or a solution-side recovery circuit rather than a refining cell.

What the customer receives is therefore bounded and documented. The machine arrives as function-tested modules with material certificates; the site interface schedule tells the builder what to prepare; installation, pressure testing of the electrolyte circuit and electrical checkout are supervised; the operators are trained on the actual equipment and sign off the standard operating procedures; the production trial runs on the customer’s own anode and the result is written into a performance certificate; and every subsequent lot leaves with a feed assay, an electrolyte assay, a slime assay, a product assay, a parameter log and a retained reference sample. The deliverable is a released, certificated ingot produced on a machine whose behaviour for that lot is a matter of record.

Key Facts

Rated output, defined: a gold electrolysis machine is rated on fine gold deposited on the cathode — the refined product, weighed after washing and drying — not on the weight of crude gold charged and not on the weight of anode plate consumed. Most quotations in this market never say which of the three they mean, which is why two machines of the same nominal drum size can look 40% apart on price and be 40% apart on output.
Accepted anode: crude gold of Au ≥ 90% with silver ≤ 6% and copper ≤ 2%; Au ≥ 95% is the preferred operating band, because both anode dissolution and plate integrity fall away as the base-metal load rises.
Silver is the gate, not gold. Silver in the anode oxidises to insoluble silver chloride and coats the anode face until dissolution stalls. It is the first number established in the feed survey and it is what decides whether a lot is admitted to the machine or parted first.
One campaign: 10–20 h of machine time per lot, set by the anode plate thickness and the current programme the lot is given.
Electrical basis: cathode current density up to 1,000 A/m² in a 1–3 V cell, with a superimposed alternating component that keeps the silver chloride film off the anode surface rather than letting it build.
Electrolyte: chloride system held at 120–150 g/L gold and 60–70 °C, with automatic level dosing and a condenser that returns the vapour to the cell instead of losing it to the extraction duct.
Product: Au ≥ 99.99% as the standard release against a fire assay with an ICP-OES cross-check, or 99.999% by running first-pass gold as the anode of a second campaign.
Metal loss: below 0.02% of the gold charged, achieved by the sealed headspace and the condenser rather than by operator care.
Configuration: cell size, cathode area, rectifier rating, installed power, footprint and site services are engineered to your anode assay and target daily output, stated as figures in the process design package rather than selected from a catalogue of fixed models.

Product Core Selling Points

The rating is defined before it is quoted. This page states that the number is fine gold deposited on the cathode, so a quotation can be compared with another quotation instead of with an adjective. It is the first thing a buyer should demand and the last thing most suppliers volunteer.
The site services are itemised in the offer. Rectifier rating, circulating pump duty, condenser duty, hood exhaust volume, cooling water, compressed air, floor loading, drainage and the effluent interim store are listed as a schedule with a value against each line — engineered to your assay and your target output rather than left as “utilities required”. Site services are the single most common cause of a commissioning delay, and no competitor page in this market even enumerates them.
One machine, one operating cycle, one operator. The cycle from charged anode to released ingot runs on a staged programme on the panel: ramp, deposit, draw, wash, dry, weigh, cast, reset. The operator’s job is to watch the readings that matter and to pull the anode for inspection on schedule, not to improvise a process.
The silver ceiling is stated, and so is the way round it. A lot above 6% silver is not sold a machine it will choke on. It is routed to parting or to the silver circuit first, and the machine is quoted for the material that comes out of that step.
The economic floor is stated too. There is a size below which a gold electrolysis machine costs more in tied-up gold, labour and floor space than it returns. This page says where that boundary sits and what to run instead, because a machine that should not have been sold is a machine that will not be reordered.
Acceptance is by assay, not by claim. The first campaign is run on your own anode and the agreement is confirmed against measured gold recovery into the cathode, the released product assay and the declared slime content. The customer’s own laboratory is free to disagree with ours on the same sample.
Built to survive its own electrolyte. Cell and frame in polypropylene and PPH with an anti-ageing additive, busbars in titanium-clad copper, wetted parts in PP and PVDF, cathode in titanium, and a transparent sealed hood so the electrodes can be watched without opening the machine.
A rectifier that is allowed to stop the machine. Cell voltage, cell current and busbar temperature are monitored continuously and the power supply is interlocked to trip on an abnormal reading, instead of quietly running a lot to the end of a bad campaign.
Every campaign is recorded. The electrical and process record for each lot is stored and can be retrieved, so a deviation can be traced to the anode, the electrolyte or the power supply rather than argued about after the metal is cast.
Modular, so capacity is added rather than replaced. Cell count, cathode area and rectifier rating can be extended on a validated installation as your volume grows, which means the entry machine does not become stranded capital.
Consumables and spares scheduled at handover. Anode bags, filter elements, gaskets and seals, pump and dosing parts and rectifier components carry a replacement interval and an on-site stock list, so the machine is not taken out of service waiting for a part.
Running cost given as a structure you can price locally. The cost of a campaign is dominated by the gold tied up in the electrolyte, then by power, then by acid and consumables, then by labour. This page states the structure and the levers; it does not quote a per-gram figure borrowed from someone else’s power tariff and labour rate.
Delivered as a released ingot, not a jar of crystal. Washing, drying, melting, sampling, assay and the certificate of analysis are inside the machine’s scope, so the customer’s output is a saleable, certificated product rather than an intermediate that has to be sold at a discount.

Application Scenarios

Bullion refineries with an in-house electrolytic step. Operations that buy doré, scrap bullion and mixed precious metal lots and need the refining cell on their own floor, with the rated output and the services it draws known before the building is prepared.
Mint-side and refinery-side refining departments replacing an ageing cell. Installations whose existing machine is at the end of its life, where the constraint is not the chemistry but the space it occupies, the power it draws and the downtime of the changeover.
Gold mines producing doré on site. Mine bullion that has been smelted at the carbon elution or gravity circuit and sits below the purity the receiving refinery will accept, upgraded at the mine where the silver and base metal load allows direct electrolysis.
Jewellery manufacturers and casting houses. Sprues, rejected castings, bench sweeps, polishing dust and returned product accumulated across a production year, consolidated into anode plates and brought back to fine gold the workshop can re-alloy to its own specification.
Gold traders, assay offices and vaulting operations. Buyers of mixed karat scrap and second-hand bullion who need to establish the true fine-gold content of a lot, convert it to a standard saleable form, and hold a documented mass balance on metal that belongs to someone else.
Electronics and printed circuit board recyclers. Facilities already recovering gold from finger, connector, CPU and plating strip liquors as a cemented powder or a sludge, converting that intermediate into an assayed ingot rather than selling it at a discount to its contained gold.
Copper, lead and nickel electrorefiners. Anode slime circuits where gold is concentrated alongside silver and the platinum group metals; once the slime leach has been reduced back to metallic gold, this is the machine that turns it into fine gold.
Plating and surface finishing companies. Gold recovered from plating baths, strip liquors and rinse waters as a powder or a cemented precipitate, re-melted into an anode and refined back to plating-grade gold or to bullion.
Secondary refiners running toll campaigns. Multi-customer operations that need a machine which can be drained, cleaned and re-charged quickly between campaigns, with the current programme and the electrolyte window re-specified from one lot to the next.
Operations constrained by building services rather than by budget. Sites with limited power, restricted floor loading or no cooling water, where the machine has to be sized against the services the building can actually provide — the reason the interface schedule exists as a document rather than as an assumption.
Pilot and laboratory metallurgy facilities. Small-batch installations used to establish how a particular anode behaves on a few kilograms before a production machine is committed, and to train operators on electrode handling and electrolyte discipline.
Dental, laboratory and medical alloy processors. Dental casting alloys, laboratory crucibles and spent precious metal ware, parted where the base metal and silver content requires it and refined to fine gold in house.
Watch, eyewear and luxury goods makers. In-house recovery from manufacturing scrap and returned product, where the lots are small, the value per lot is high and the material is frequently irreplaceable.
Industrial operations with an in-house precious metal unit. Catalyst, electronics, chemical and glass manufacturers that accumulate gold-bearing residues and want the refining step inside their own compliance envelope rather than exporting the metal as waste.
Refineries whose constraint is the working capital held in process. Businesses that have worked out that the gold tied up in electrolyte and in residual plate is a real cost of ownership, and that want a machine specified with that figure stated rather than left to grow with the tank.

Applicable Raw Materials

The machine is fed anode plates, and what decides whether a lot is admitted is its gold, silver and copper figures rather than its commercial description. Each feed below enters the machine at the point its composition allows: material inside the working window is cast to anodes and run directly, material above the silver ceiling is parted before casting, and material arriving as a powder, a slime or a cemented precipitate is dried, fluxed and consolidated into a cast anode first. Output is stated for each feed.

Mine doré bars and smelted bullion. Button and bar doré from a carbon elution or gravity circuit smelt, carrying gold with silver and a modest base-metal load, admitted directly where the silver figure sits inside the working ceiling. Output: Au ≥ 99.99% ingot; silver recovered from the anode slime.
Crude gold anode plates cast from retorted or cemented gold. Cemented, retorted or ion-exchange-derived gold powder that has been melted, fluxed and cast to plate geometry; the standard feed of a secondary refinery and the case for which the machine’s rated output is normally quoted. Output: Au ≥ 99.99% ingot; slime to the silver and platinum group metal circuits.
Gold reduced from chloride or aqua regia solution. Powder produced by selective reduction from a chloride liquor, washed free of residual nitrate and chloride, dried and melted to an anode; the interface between a wet chemical refining line and the electrolytic machine. Output: Au ≥ 99.99% ingot; second-pass material to 99.999% where required.
Karat jewellery scrap after inquartation and parting. 18K, 14K and 9K scrap and old gold melted with silver or copper, granulated and parted in nitric acid so the silver and base metals leave before the gold is cast into anodes. Output: Au ≥ 99.99% ingot; silver nitrate solution to the silver circuit.
Bench sweeps, polishing dust and workshop residues. Incinerated, milled, blended and sampled material from jewellery manufacture, smelted to an anode after the organics have been burned off and ferrous contamination removed. Output: Au ≥ 99.99% ingot; slag returned for re-milling.
Gold-bearing anode slime after leaching and reduction. Gold recovered from copper, lead or nickel electrorefining slime, reduced back to metal, melted and cast; frequently the highest-value lot a secondary refinery handles. Output: Au ≥ 99.99% ingot; silver and platinum group metal fractions separated upstream and downstream.
Electronic scrap gold concentrate. Gold from fingers, connectors, CPU packages and plating strip liquors, recovered as a cemented powder or a sludge and cast to anodes; the base-metal load is usually why this material is electrolysed rather than sold as a concentrate. Output: Au ≥ 99.99% ingot; copper and nickel retained in the electrolyte and bled off.
Deplated and stripped coating gold. Gold recovered from stripped watch cases, spectacles, connectors and decorative ware, collected as a foil or a powder and consolidated into an anode. Output: Au ≥ 99.99% ingot.
Silver electrolysis anode slime. Gold retained in the anode bag of a silver refining cell, parted to a gold-rich residue assaying above 90% and cast to plate; the standard two-stage route when the silver in the feed is worth more than the gold. Output: Au ≥ 99.99% ingot; silver recovered upstream.
Dental and laboratory alloy scrap. Dental casting alloys, laboratory crucibles, electrodes and precious metal ware, parted where necessary and cast to anodes for the machine. Output: Au ≥ 99.99% ingot; platinum group metal content to the PGM circuit.
Gold–silver and gold–PGM alloy scrap. Au–Ag strip, Au–Pt and Au–Pd alloy scrap and brazing alloys, where the anode is high-grade in gold but carries a platinum group metal load that reports to the anode slime rather than to the electrolyte. Output: Au ≥ 99.99% ingot; PGM concentrate from the anode slime.
Recycled bullion, coin and bar material. Old bars, coins and bullion whose provenance requires re-refining before resale, run as anode plates cast directly from the melted material. Output: Au ≥ 99.99% ingot with a fresh certificate of analysis.
Gold recovered by electrowinning or cementation. Cathode sludge and cemented precipitate from solution-side recovery circuits, dried and melted to anodes; the standard route by which gold recovered from a liquor is brought up to bullion standard. Output: Au ≥ 99.99% ingot.
Consigned and toll-refining lots. Customer-owned gold run as a discrete campaign with its own mass balance, parameter log and retained sample, consolidated into anodes and refined on a per-lot basis. Output: Au ≥ 99.99% ingot with a lot-specific mass balance and certificate.
First-pass gold returned as second-campaign feed. Gold that has already passed through one campaign, cast as an anode and charged again to reach 99.999%, either as plate cast from first-pass cathode gold or as crystal returned to the cell. Output: 99.999% gold ingot with a separate certificate of analysis.
Feeds that are not admitted. Low-grade ore, un-stripped electronic scrap, plating rinse waters and dilute liquors are not anode material and are not run on this machine. Ore and scrap need mechanical and pyrometallurgical concentration first; rinse waters and dilute liquors belong on a solution-side recovery circuit. Output: routed upstream or to the recovery circuit, with the boundary stated at quotation.
Feeds admitted only after parting. Anodes above 6% silver, or above 2% copper, are parted before they are cast, because silver chloride film will stall dissolution and copper above the working limit reports to the cathode and costs grade. Output: parted gold to the anode mould; silver to the silver circuit.

Finished Products

The machine is configured around the product form the customer sells, holds or re-uses, from cathode gold crystal through to a certificated ingot. Where the customer already operates a melting and assay shop, the machine is delivered with the cell, harvesting and drying stages only; where it does not, the melting, casting, sampling and assay equipment is inside the scope.

Fine gold ingot and button. The primary output, poured from cathode gold and assaying 99.99% and above, released against a fire-assay determination with an ICP-OES cross-check and accompanied by a certificate of analysis. Output: certificated fine gold ingot or button.
99.999% gold. Produced by charging first-pass gold as the anode of a second campaign, for buyers whose own specification or downstream qualification calls for the higher standard. Output: 99.999% gold ingot with a separate certificate of analysis.
Cathode gold crystal and deposits. The as-deposited product harvested from the cathode before melting, supplied where the customer prefers to handle, sample or re-melt the metal in its own furnace. Output: washed and dried cathode gold crystal at declared purity.
Anode slime — silver chloride fraction. The silver carried in the anode, rejected at the anode face as silver chloride and retained inside the anode bag, supplied as a washed and dried intermediate to the silver circuit or to a customer who refines silver in house. Output: silver chloride slime at declared silver content.
Anode slime — platinum group metal fraction. Platinum, palladium, rhodium and iridium carried in the anode and rejected into the same residue, supplied as a dried high-grade concentrate declared by metal content. Output: PGM-bearing anode slime routed to the PGM refining line.
Residual anode plate and hanger residues. Plate that has reached the end of its dissolution cycle, returned to the melting furnace and cast into fresh anodes rather than sold as scrap. Output: remelted anode stock returned to the machine.
Electrolyte bleed solution. Electrolyte withdrawn on the defined bleed schedule to hold the silver and base-metal concentration inside the working window, containing gold that is recovered before the bleed leaves the plant. Output: gold recovered from the bleed; silver- and base-metal-bearing solution to the silver circuit.
Rebuilt electrolyte returned to the machine. Fresh chlor-auric acid made up and returned to the circuit after gold recovery from the bleed, holding the working gold tenor inside the control band. Output: electrolyte at 120–150 g/L gold, returned to service.
Recovered fume condensate. Electrolyte condensed from the sealed headspace and returned to the machine rather than vented, which is the mechanism behind the sub-0.02% metal loss figure. Output: electrolyte returned to the cell; acid mist removed from the working atmosphere.
Gold-bearing filter media and container rinses. Filter cartridges, bag cloth, gaskets and container washes from the electrolyte circuit, processed rather than discarded so entrained gold leaves the plant as metal rather than as waste. Output: recovered gold returned to the melting station.
Campaign record, certificate and retained sample. Every lot is released with the anode assay, the electrolyte assay, the slime assay and the product assay, the parameter log for the campaign, and a retained reference sample held for the warranty period. Output: campaign record and certificate of analysis.

Gold Electrolysis Machine Process Flow

The nine stages below are one operating cycle of the machine, from the lot registration that checks the unit is configured for the material through to a released ingot and a machine reset for the next campaign. Stages 4 and 5 are where the cycle is decided and where it is protected: the current programme set at Stage 4 is what produces a coherent seed deposit rather than a burst of nodules, and the alarm response at Stage 5 is what stops a fault from running to the end of a lot. The electrochemical design basis behind the setpoints — cell voltage as a diagnostic, silver chloride control, the electrolyte window and the working gold inventory — is set out on the gold electrolysis equipment page; this page covers the machine’s own cycle and what the operator does inside it. Engineering setpoints are fixed during process design against your own anode assay and confirmed on the production trial.

Gold electrolysis machine flow — one full operating cycle, from a registered lot to a released 99.99% ingot, with the silver chloride slime and the electrolyte rebuild closed on the same machine.

Steps 1 — Lot Registration and Machine Configuration Check. The lot is registered against a campaign number before anything is charged, and the machine is checked against the configuration recorded for that material. The feed assay is entered — gold, silver, copper by ICP-OES with the gold cross-checked by fire assay, and the platinum group metal inventory declared — and the operator confirms that the anode geometry, the cathode set, the electrolyte window and the current programme on the route sheet match the assay in hand. Where the lot sits outside the working window, the route sheet directs it to parting before casting rather than to the machine, and the decision is recorded. Anode plate dimensions and cast weights are checked against the schedule, since a plate cast outside tolerance changes the inter-electrode distance along its length and produces an uneven current distribution that is difficult to diagnose once the headspace is closed. Reagent and utility input: lot weighing and registration, riffling and sample splitting, fire assay and ICP-OES, route sheet and configuration record. Output: a registered lot with its machine configuration confirmed; anode geometry and weight verified against the schedule.

Steps 2 — Anode Casting and Cell Loading. The assayed feed is melted under flux and cast into anode plates of controlled thickness and envelope, or, where the lot arrives as a powder, a slime or a cemented precipitate, dried, fluxed and consolidated into a cast anode rather than fed loose. Each plate is bagged or fitted with a membrane before it goes near the cell, because silver chloride and platinum group metal residue are insoluble and will reach the cathode and cost grade if they are free to move. The plate is fitted to its titanium-clad copper hanger, contact faces are cleaned and dressed, and the assembly is checked for straightness and immersion depth. The cathode set is prepared in parallel — titanium plate degreased and passivated, or a pure gold seed sheet fitted and checked for flatness — and every cathode is positioned at the design inter-electrode distance with the spacing system. Busbar contact faces are cleaned on both sides before the clamps go on, because a resistive contact on a single cathode is the hardest fault to find once the headspace is sealed. Reagent and utility input: melting furnace with flux and anode mould set, anode bags or membranes, hangers, cathode plates or seed sheets, degreasing and passivation agents, spacing gauge, contact dressing. Output: bagged anode assemblies and a prepared cathode set, all at verified spacing and contact.

Steps 3 — Electrolyte Charging and Tenor Verification. The electrolyte is charged to the machine at the working gold tenor and free acid band fixed in process design, having been made up in the preparation vessel with agitation, metered acid addition and fume extraction. Gold is present as the tetrachloroaurate ion at 120–150 g/L in the standard design, which is what makes the liquor conducting and what sets the working inventory the machine ties up; free acid is held in the band that keeps the complex stable. Before the power is applied the temperature loop is brought to the 60–70 °C working band and the liquor is circulated to break up stratification of the denser gold-rich solution at the bottom of the tank. The charged electrolyte is sampled and analysed for gold and free acid, and the result is recorded against the campaign — an unassayed electrolyte is the most common cause of a disappointing first run, and it is a fault that cannot be corrected once deposition has begun. Reagent and utility input: chlor-auric acid electrolyte, hydrochloric acid with metered dosing, preparation vessel with extraction, circulation pump, temperature control loop, gold and free acid analysis. Output: electrolyte charged at the working tenor and temperature with a recorded make-up analysis.

Steps 4 — Power Ramp and Current Programme Selection. The rectifier is brought up on the staged programme written for the lot rather than switched on at working current, because the first minutes of a campaign decide the structure of the whole deposit. A modest initial current builds a coherent, fine-grained seed layer that stays coherent as it thickens; a cold start at full current produces a burst of nodules that shed back into the electrolyte and are recovered as slime rather than as product. The current programme is selected from the route sheet against the anode’s silver content and the cathode area, and the AC-DC superposition unit is set so that the alternating component that sheds silver chloride from the anode face is active from the first hour. Per-cathode currents are checked individually after start-up, cell voltage is compared with the design figure and busbar temperature is confirmed stable before the machine is left to run. Reagent and utility input: adjustable current-limited rectifier, AC-DC superposition unit with adjustable alternating component, staged current programme, per-cathode current check, busbar temperature monitoring. Output: a coherent seed deposit established, current distributed evenly across the cathode set and the silver chloride film held in check from the outset.

Steps 5 — Supervised Deposition and Alarm Response. This is the longest stage of the cycle and the one the panel exists for. Deposition runs at a cathode current density up to 1,000 A/m², with circulation refreshing the boundary layer at the cathode face and the temperature loop holding the electrolyte in its band. Cell voltage, cell current and busbar temperature are logged continuously, and an abnormal reading trips the rectifier instead of being allowed to run to the end of the lot. The operator’s scheduled work is inspection rather than intervention: the anode is lifted on the interval the silver load dictates, the anode face is examined for film build-up and any accumulated chloride is brushed clear, and the electrolyte is sampled so the bleed decision is taken on the assay rather than on appearance. Voltage is treated as a symptom — a rise at constant current is worked through contact resistance, electrode spacing, electrolyte conductivity and temperature before anything else is touched, and a dark or poorly adherent cathode is corrected by reducing voltage rather than by raising it. Reagent and utility input: rectifier at design current, circulation and agitation, temperature control, anode inspection and cleaning tooling, electrolyte sampling, PLC interlock and alarm log. Output: gold deposited to the design load, faults caught inside the cycle and corrected settings recorded against the campaign.

Steps 6 — Cathode Draw and Crystal Washing. When the cathode has taken up its design load — judged from the ampere-hours passed against the deposit weight and confirmed by weighing the drained cathode — the machine is de-energised, the current is brought down on the ramp, and the cathode set is lifted. The deposit is washed immediately to remove adhering electrolyte, because electrolyte left on the crystal carries gold out of the machine in the wash water, loads the melt with chloride and is the single easiest way to lose metal from an otherwise clean campaign. The wash water is collected and returned to the circuit rather than sent to the effluent plant, and the containment tray under the cell is drained and its liquor recovered on the same principle. Cathode handling uses the lifting frame rather than improvised hooks, so the deposit is never dragged across the cell edge and the electrodes are not distorted for the next campaign. Reagent and utility input: cathode lifting and handling frame, washing station with collected wash water, containment tray drainage, wash water return to the circuit. Output: washed cathode gold; wash water and tray liquor returned to the machine.

Steps 7 — Drying, Weighing and Charge Reconciliation. The washed cathode gold is dried to constant weight and weighed, and that weight is reconciled against the ampere-hours passed and against the anode weight consumed before the lot is allowed to move to the melt. The reconciliation is the machine’s own check on itself: a deposit materially lighter than the charge predicts points to current lost to water decomposition, to a contact resistance that went unnoticed, or to gold that has gone into the electrolyte rather than onto the cathode, and each of those has a different remedy. Anode plates are weighed again at this point, and any residual plate still carrying appreciable gold is set aside for remelting rather than treated as spent. The weighed figures, the ampere-hours and the electrolyte sample result are entered against the campaign number, so the lot carries a metal balance forward to the melt instead of relying on a visual judgement of how full the cathode looked. Reagent and utility input: drying oven, calibrated balance, ampere-hour and current records, anode re-weighing, campaign record entry. Output: a weighed deposit reconciled against charge, plus residual anode stock identified for remelting.

Steps 8 — Slime Draw, Filter Change and Electrolyte Top-Up. The anode bags are opened and the slime that has accumulated at the anode face during the campaign is washed free of entrained electrolyte, dried, weighed and sampled for silver and for any platinum group metal content, so that the by-product leaves the machine as a declared material rather than as bag waste. The electrolyte circuit is serviced on the same schedule: the filtration elements that protect the anode bags and the deposit are changed, the level is topped up by the automatic dosing system to replace the liquor carried out with the fume, and the working liquor is analysed for gold, free acid, silver and base metals so that the bleed can be taken on the assay rather than after the machine has started to behave badly. Where the electrolyte has loaded with copper or other base metal, the bleed is withdrawn at this point, its gold recovered, and the rebuilt electrolyte returned to the machine at the working tenor. Reagent and utility input: bag opening and slime washing station, vacuum or pressure filtration, drying oven, slime and electrolyte assay, filter elements, level dosing make-up, bleed and electrolyte rebuild. Output: washed and assayed anode slime with its silver and PGM fractions declared; rebuilt electrolyte returned to service.

Steps 9 — Ingot Casting, Assay and Machine Reset. The dried and reconciled gold is melted under a flux formulation matched to the deposit, sampled from the melt, and cast to the product form the customer sells — ingot, button or granule — with the ingot marked and its weight recorded against the campaign. The cast product is analysed by fire assay with an ICP-OES cross-check, and the lot is released only when the analysis confirms the specified grade, so the machine’s output is a certificated ingot rather than a purity claim. The machine is then reset for the next lot: the cell, hood, condenser, ducting and filter housings are cleaned on the same schedule, the recovered condensate is returned to the cell, the electrodes are inspected and the cathode set is prepared or replaced, and the next campaign’s configuration is loaded against its own assay. The campaign’s mass balance — anode in, ingot out, slime out, electrolyte in circuit and losses accounted for — is closed and issued with the certificate of analysis. Reagent and utility input: melting furnace with flux and mould set, sampling and fire assay, ICP-OES cross-check, ingot marking, cell and condenser cleaning, electrode inspection, cathode re-preparation, mass balance reconciliation. Output: a released, certificated 99.99% ingot; a closed campaign mass balance; a machine reset for the next lot.

Product Structure (Main Equipment)

The machine is assembled from the six module groups below. Materials of construction are selected for hot chloride duty and for the small quantity of electrolyte that inevitably escapes the circuit: cell body and frame in polypropylene and PPH with an anti-ageing additive, busbars in titanium-clad copper, anode bags in acid-resistant woven polymer, wetted piping and ducting in PP and PVDF, and a hood in transparent polymer so the anode face and the deposit can be watched without opening the machine.

Machine frame, cell and containment

Machine frame and cell support. Welded structural frame in PPH that carries the cell, the electrode loads and the hood, and that sets the cell at the working height for anode inspection and cathode handling without a working platform. Output: a level, corrosion-resistant machine base with defined electrode access.
Electrolytic cell body. Integrally formed polypropylene or PPH tank with an anti-ageing additive, welded rib reinforcement and a sealed base, formed in one piece so that the electrolyte circuit does not weep at a joint over the life of the machine. Output: the primary process vessel.
Containment tray and cell floor. Acid-resistant tray under the cell that holds any spill or drainage for recovery instead of letting it reach the floor drain, and a floor finish that can be washed down without carrying gold out of the refining area. Output: spill containment with the liquor recoverable.
Cell lid and sealed headspace frame. Sealed lid on an acid-resistant frame that closes the cell against the working area and carries the duct connection to the condenser under negative pressure. Output: an enclosed cell with a controlled vapour path.

Electrode assemblies and busbar set

Anode hangers, hooks and contact bars. Titanium-clad copper hangers that carry each plate at the design immersion depth with machined contact faces; the hanger is the anode’s only electrical connection and its condition is the first suspect when cell voltage rises. Output: mounted anode assemblies at a verified immersion depth and contact resistance.
Anode bags and membrane frames. Acid-resistant bag or membrane assemblies fitted to each anode to retain the insoluble silver chloride and PGM residue at the anode face and keep it out of the cathode deposit. Output: contained anode residue with the deposit protected.
Cathode assemblies. Titanium plates selected for clean stripping and freedom from second-metal contamination, or pure gold seed sheets where a titanium contact is unacceptable in the customer’s specification; supplied as a matched set with hanger bars and insulated supports. Output: the deposition surface and the deposit carrier.
Cathode position and spacing system. Insulated retaining comb or spacer system that holds every cathode at the design inter-electrode distance from its anode along the full immersed length, which is what keeps the current distribution even and prevents a localised burn. Output: uniform electrode spacing and even current distribution.
Busbar set and compression contacts. Titanium-clad copper busbars with machined contact faces, compression clamps and insulated supports, sized to carry the full cell current with minimal voltage drop and arranged so that each cathode can be metered individually. Output: even current distribution and a measurable base for fault detection.
Electrode lifting and setting frame. Lifting frame for anodes, cathodes and the cell lid, designed so that routine inspection and harvest do not depend on improvisation and the electrodes are never dragged across the cell edge. Output: safe and repeatable electrode handling across campaigns.
Anode inspection and cleaning tooling. Inspection station with non-metallic scraping and brushing tools used to examine the anode face and dislodge accumulated chloride on the schedule the silver load sets. Output: inspected and cleaned anode returned to service.

Power conversion, control and interlock cabinet

Electrolytic rectifier. Adjustable, current-limited DC supply with a voltage range covering the 1–3 V working window and the headroom the start-up ramp requires, sized to the cell current the cathode area and the electrolyte support. Output: controlled direct current to the electrode set.
AC-DC superposition unit. Superimposed alternating current module with an adjustable alternating component, fitted to break the silver chloride film away from the anode face continuously so that the plate dissolves to completion instead of passivating. Output: sustained anode dissolution on silver-bearing anodes.
Enclosed, isolated cabinet. The rectifier, its superposition unit and the control gear sit in their own compartment, physically separated from the cell atmosphere so that acid vapour does not attack their internals — the single largest determinant of power supply service life in a gold refining room. Output: extended power and control service life.
PLC control and operator interface. Touch-screen panel controlling the rectifier, circulation, heating, dosing and filtration, running a staged automatic cycle in which each stage carries its own voltage and duration, with a manual mode available for intervention and for anode inspection. Output: repeatable automatic cycles and reproducible campaigns.
Voltage, current and busbar temperature monitoring. Continuous measurement of cell voltage, cell current and busbar temperature with interlocks that trip the rectifier on an abnormal reading rather than allowing a fault to run to the end of a lot. Output: faults detected before they become unrecovered metal.
Parameter logging and campaign history. Storage and retrieval of the electrical and process record for every campaign against its lot number, so a deviation can be traced to the anode, the electrolyte or the power supply rather than guessed at after casting. Output: a per-campaign process record filed with the assay results.
Alarm and interlock schedule. A defined alarm list with set points and trip actions covering over-voltage, over-current, busbar over-temperature, electrolyte over-temperature, loss of circulation, low level and loss of extraction, so that a fault has one documented response rather than an improvised one. Output: a documented alarm response for every monitored parameter.

Electrolyte circuit and temperature control

Electrolyte preparation vessel. Agitated vessel with metered acid dosing and fume extraction in which chlor-auric acid electrolyte is made up to the working gold tenor and free acid band. Output: electrolyte made up to specification with a recorded make-up analysis.
Electrolyte circulation pump. Acid-resistant pump with PP or PVDF wetted parts that keeps the electrolyte moving through the cell, refreshing the boundary layer at the cathode face and preventing stratification of the denser gold-rich liquor at the bottom of the tank. Output: uniform electrolyte composition and a sustained mass-transfer rate.
Temperature control loop. Heating and, where the duty requires it, cooling system with a temperature probe and controller that holds the electrolyte in the 60–70 °C working band, which is fixed by the chemistry rather than by preference. Output: electrolyte held in the working temperature band.
Automatic level dosing system. Level sensing with metered make-up addition that replaces the electrolyte carried out with the fume, so the machine neither runs down in level nor drifts in concentration between shifts. Output: electrolyte level and concentration held inside the control band.
Electrolyte filtration. Cartridge or bag filtration ahead of the cell removing suspended solids that would otherwise blind the anode bag, plate onto the cathode and contaminate the deposit. Output: particle-free electrolyte.
Gold and free acid monitoring. Sampling and analysis regime with the glassware and instrumentation needed to determine gold, free hydrochloric acid, silver and base metals in the working liquor, so that the bleed decision is taken on measurement rather than on appearance. Output: an electrolyte assay trend used to set the bleed schedule.
Bleed tank and gold recovery from the bleed. Tank that receives electrolyte withdrawn on the bleed schedule together with the equipment that recovers its gold before the liquor leaves for the silver circuit. Output: gold returned to the melting station; silver-bearing bleed to the silver circuit.

Headspace capture, condensation and abatement

Transparent sealed hood. Enclosing hood with a transparent viewing panel and a sealed perimeter, fitted over the cell so the headspace is captured rather than vented into the workshop, and so the anode face can be watched during the campaign. Output: an enclosed cell with the process visible.
Electrolyte condenser. Condenser on the vapour line that recovers evaporated electrolyte and returns it to the cell, which is the equipment that holds metal loss below 0.02% of the gold charged and keeps the working area free of acid mist. Output: electrolyte condensed and returned; acid mist removed from the working atmosphere.
Exhaust ducting and fan. Ducting sized to the hood exhaust volume and run under negative pressure so that any leakage is inward, with a fan rated for acid vapour duty. Output: controlled vapour extraction at the point of generation.
Alkali scrubbing tower with demister. Scrubber that removes residual acid mist and any chlorine carried through the condenser before the air is released, with a demister to prevent droplet carry-over. Output: scrubbed off-gas with the scrubber liquor analysed and logged.
Nitrogen oxide abatement. Absorption stage added where the plant also operates nitrate-based pre-treatment, dosed with oxidant so nitrogen oxides are converted rather than carried through. Output: abated off-gas meeting the site discharge limit.
Effluent neutralisation and settling. Neutralisation and settling for the wash water and spent liquors that cannot be returned to the circuit, with the hydroxide sludge routed back for metal recovery rather than discarded. Output: compliant effluent; recovered residual metal.

Harvest, casting, assay and campaign records

Cathode washing station. Washing station with collected wash water in which the harvested cathode is rinsed free of adhering electrolyte before drying, so gold is not carried out of the machine on the crystal and chloride does not enter the melt. Output: washed cathode gold and wash water returned to the circuit.
Drying oven and balance. Controlled-temperature oven for the cathode gold, the anode slime and the filter cake, with a calibrated balance for the deposit weight that is reconciled against the ampere-hours passed. Output: dry, weighed material ready for melting, assay or reconciliation.
Melting furnace, flux and mould set. Induction or resistance furnace with a flux formulation matched to the deposit and a mould set for the product form required, whether that is an ingot, a button or granules. Output: cast precious metal product with a recorded weight.
Sampling and assay station. Fire assay apparatus, ICP-OES, sample preparation and a dedicated fume hood, so that the anode, electrolyte, slime and product assays for a campaign are produced in house on the day the campaign closes. Output: a certificate of analysis issued against the campaign.
Slime washing, filtration and drying train. Vacuum or pressure filtration with a drying oven for the anode bag contents, so the silver and PGM fraction can be washed, dried, weighed and declared by metal content. Output: washed and assayed anode slime declared by metal content.
Campaign record set and retained sample store. Sealed store holding the feed, intermediate and product samples for each lot for the warranty period, with the parameter log, the metal balance and the certificate of analysis filed against the same campaign number. Output: a retained reference sample and a complete campaign record.
On-site spares and consumable set. The wearing items the machine consumes — anode bags, filter elements, gaskets and seals, pump and dosing parts and rectifier components — supplied with a recommended stock list and a replacement interval so the machine is not idle waiting for a part. Output: a stocked spares position from the day of handover.

Product Features

A published rating basis. The machine is rated on fine gold deposited on the cathode, and the basis is written into the process design package, so a quotation can be compared with another quotation rather than with a claim.
A site interface schedule instead of a utilities note. Rectifier rating, circulating pump duty, condenser duty, hood exhaust volume, cooling water, compressed air, floor loading, drainage and effluent interim storage are listed with a value against each line.
One operating cycle on one panel. Ramp, deposition, harvest, wash, dry, weigh, cast and reset run as a staged automatic programme with a manual mode for anode inspection, so campaigns do not depend on operator memory.
Assay-gated admission. The feed survey decides whether a lot is run directly or parted first, and the silver and copper ceilings are stated as figures rather than as warnings, so no lot is charged to the machine that will passivate in it.
A rectifier built for a refining room. The power supply and its superposition unit sit in a compartment isolated from the acid vapour in the working area, which is what decides how long they last.
Sealed headspace with electrolyte condensation. A hot chloride electrolyte evaporates and the vapour carries gold, so the machine is closed and the vapour is condensed and returned rather than extracted and lost.
Metal loss below 0.02% of the gold charged. Stated as a consequence of the sealed hood and the condenser rather than as an operating aspiration, and checkable against the campaign mass balance.
Deposit weight reconciled against ampere-hours. The deposit is weighed and reconciled against the charge before the lot moves to the melt, so a loss of current to water decomposition or a hidden contact resistance is caught inside the campaign.
Anode bags fitted as a matter of design. Insoluble silver chloride and PGM residue are held at the anode face rather than allowed to reach the cathode, which protects both the product grade and the saleable value of the by-product.
An alarm list with set points and trip actions. Over-voltage, over-current, busbar over-temperature, electrolyte over-temperature, loss of circulation, low level and loss of extraction each have a documented response rather than an improvised one.
A campaign record per lot. Feed assay, electrolyte assay, slime assay, product assay, parameter log, mass balance and retained sample are filed against the same campaign number.
Release against assay, not against appearance. The lot is certificated only when a fire assay with an ICP-OES cross-check confirms the specified grade, and the customer’s own laboratory is free to disagree on the same sample.
Modular capacity. Additional cell capacity, cathode area and rectifier rating can be added to a validated machine as volume grows, rather than replacing an installation that has already been proved on the customer’s own material.
A stated consumable schedule. Anode bags, filter elements, gaskets and seals, pump and dosing parts and rectifier components carry a replacement interval and a recommended on-site stock list issued at handover.
Running cost as a structure rather than a borrowed figure. The levers are named in the order they matter — the gold tied up in the electrolyte first, then power, then acid and consumables, then labour — and the cost is priced per project against the customer’s own power tariff and labour rate.
A silver route alongside the machine. Where the feed sits above the working ceiling, the quotation names the parting step or the silver circuit that has to run ahead of it rather than selling a machine that will not dissolve the plate.
An economic floor stated openly. The size below which a refining cell cannot carry its own working inventory, supervision and floor space is stated, together with the alternatives, because a machine that should not have been sold is a machine that will not be reordered.
Materials selected stream by stream. Polypropylene and PPH with an anti-ageing additive for the cell and frame, titanium-clad copper for the busbars, titanium for the cathode plates, acid-resistant polymer for the bags, and PP and PVDF for the wetted piping and ducting.
Anode-side gold returned to the machine. Residual plate, hanger residues and cell-bottom material go back to the melting station and into fresh anodes, which is how the anode gold balance is closed.
Melting, sampling and assay inside the scope. The customer receives a certificated ingot with a fire-assay determination, an ICP-OES cross-check and a retained reference sample, not a jar of crystal and a purity claim.
Integration with the wider flowsheet. Gold from a solution-side recovery circuit, a cementation step or an ion exchange column feeds straight in as anode stock, the silver chloride slime leaves for the silver circuit and the PGM fraction leaves for the PGM line.

Technical Parameters And Specifications

The figures below are the standard design basis and are confirmed or adjusted during process design once the anode assay is known. Cell size, cathode area, rectifier rating, installed power, footprint and site services are engineered to your anode assay, silver load, target daily output and building services rather than taken from a catalogue of fixed models.

Gold electrolysis machine — technical parameters and specifications.

Parameter	Specification
Machine type	Self-contained electrolytic refining unit: cell and electrode assemblies on one frame, power and control cabinet, electrolyte circuit, sealed headspace with condenser and scrubber, harvest and casting station
Process basis	Anodic electrorefining in which the cast crude-gold anode is both the feedstock and the electrochemical reactant; fine gold is deposited on a seeded cathode and released as a certificated ingot
Boundary against neighbouring equipment	Downstream of dissolution, reduction and anode casting; a solution-side recovery circuit recovers gold from liquors and is a different machine, and a hydrometallurgical plant dissolves and separates material that is not yet metal
Rated output — unit definition	Fine gold deposited on the cathode, weighed after washing and drying and reconciled against the ampere-hours passed; not the weight of crude gold charged and not the weight of anode plate consumed
Capacity, rated output	Engineered to your anode assay, silver load, target daily gold output, shift pattern and building services, and stated as a figure in the process design package rather than selected from a fixed model list
Capacity — what sets it	The gold content of the anode fixes the metal to be dissolved; the silver content fixes how hard the anode can be driven and therefore the cathode area; the copper content fixes the bleed frequency; the target daily output and shifts fix the cell count
Feed gold content	Au ≥ 90% admitted for direct electrolysis; Au ≥ 95% preferred, because anode dissolution and plate integrity both fall away as the base-metal load rises
Feed silver content	≤ 6% in the anode for direct running; above that the lot is parted — by nitric acid where the gold-to-silver ratio allows it, or through the silver circuit — before it is cast
Feed copper content	≤ 2% in the anode; above that copper reports to the cathode and costs grade, and the electrolyte loads faster and needs a shorter bleed interval
Feed platinum group metal content	Reports to the anode slime rather than to the electrolyte; declared in the feed assay and separated on the slime circuit
Feed forms accepted	Mine doré and smelted bullion, cast crude gold plates, gold reduced from chloride or aqua regia solution, karat scrap after parting, bench sweeps and workshop residues, slime-derived gold, electronic scrap gold concentrate, deplated coating gold, silver electrolysis anode slime, dental and laboratory alloy scrap, Au–Ag and Au–PGM alloy scrap, recycled bullion and coin, electrowon or cemented gold powder, consigned toll lots, first-pass gold for a second campaign
Feeds not admitted	Low-grade ore, un-stripped electronic scrap, plating rinse waters and dilute liquors; these are routed to concentration or to a solution-side recovery circuit rather than to this machine
Feed pre-treatment	Melting under flux and casting to anode plates; incineration and milling of sweeps; inquartation and nitric parting where the silver or copper figure exceeds the working ceiling; drying and consolidation of powder, slime and cemented precipitate
Anode geometry	Cast to a controlled thickness and envelope with hanger positions and immersion depth fixed in process design, and checked for straightness so the inter-electrode distance is uniform along the immersed length
Campaign time	10–20 h of machine time per lot, set by the anode plate thickness and the current programme selected for the campaign
Shift pattern	One operator per machine across the cycle, with the panel running the staged programme and the operator carrying scheduled anode inspection, electrolyte sampling and harvest
Electrolyte system	Chlor-auric acid in hydrochloric acid, gold present as the tetrachloroaurate ion
Electrolyte gold tenor	120–150 g/L in the standard design, held inside a control band for the campaign
Free hydrochloric acid	Held in the band fixed in process design to keep the liquor conducting and the gold complex stable
Electrolyte volume and working inventory	Electrolyte volume, cell geometry, circulation and the bleed schedule are set as design outputs so that the gold tied up as solution is a known, stated and minimised figure
Electrolyte temperature	60–70 °C held by the temperature control loop; below the band the resistance rises and the plating kinetics fall away, and the upper end is bounded by evaporation and reagent loss
Cell voltage, working window	1–3 V per cell; gold deposition is the favoured reaction only inside the window, and voltage above it is spent decomposing water and roughening the deposit
Cell voltage, fault interpretation	A rising cell voltage at constant current is diagnosed in a fixed order: contact resistance, inter-electrode spacing and anode geometry, electrolyte conductivity and free acid, temperature, then the condition of the anode face
Cathode current density	Up to 1,000 A/m² on the cathode, against the 200–800 A/m² band conventional electrolytic gold and silver cells occupy
Cost of high current density	Increased IR drop across the electrolyte gap, accelerated silver chloride build-up at the anode and a greater tendency to nodular deposit growth; each is answered by the machine design rather than by reducing the current
Inter-electrode spacing	Fixed at the closest spacing that keeps electrolyte resistance low without risking dendrite or chloride bridging at the working current density, and held by the cathode spacing system along the full immersed length
Current start-up	Ramped from a fraction of the target value over a defined period on a staged voltage and time programme, to establish a coherent seed deposit before full current is applied
Silver chloride control	Superimposed alternating current shedding the film continuously, anode bagging retaining the detached chloride, an anode silver ceiling fixed in process design, and scheduled anode inspection and cleaning
Residue containment	Anode bag or membrane assembly retaining silver chloride and PGM residue at the anode face and keeping it out of the cathode deposit
Anode material	Cast crude gold plate, bagged, carried on a titanium-clad copper hanger at the design immersion depth
Cathode medium	Titanium plate selected for clean stripping, or a pure gold seed sheet where a titanium contact is unacceptable in the customer’s specification
Busbar material	Titanium-clad copper with compression clamps, machined contact faces and insulated supports, arranged so each cathode can be metered individually
Cell body material	Integrally formed polypropylene or PPH with an anti-ageing additive, welded rib reinforcement and a sealed base, formed in one piece so the circuit does not weep at a joint
Lid and hood material	Transparent polymer viewing panel in a sealed acid-resistant frame, ducted to the condenser under negative pressure
Wetted piping and ducting	Polypropylene and PVDF
Power supply	Adjustable current-limited rectifier with a range covering the 1–3 V working window and the start-up ramp headroom, plus an AC-DC superposition unit with an adjustable alternating component
Power supply location	Enclosed in its own compartment, physically separated from the cell atmosphere so acid vapour does not attack the rectifier and control gear
Electrical supply	Three-phase AC supply stepped down and rectified at the machine
Installed power	Engineered to the cathode area, current density and target daily output, and stated in the process design package
Electrolyte circulation	Acid-resistant pump and piping sized to the design circulation rate, refreshing the boundary layer at the cathode face and preventing stratification of the denser gold-rich liquor
Electrolyte level control	Automatic level sensing with metered make-up addition matched to the rate at which electrolyte leaves with the fume
Electrolyte filtration	Cartridge or bag filtration ahead of the cell removing suspended solids that would blind the anode bag, plate onto the cathode or contaminate the deposit
Electrolyte bleed	Taken on the schedule the electrolyte assay for silver and base metals dictates; gold is recovered from the bleed before the liquor leaves for the silver circuit
Fume condensation	Condenser on the vapour line returning evaporated electrolyte to the cell and holding metal loss below 0.02% of the gold charged
Off-gas treatment	Alkali scrubbing tower with a demister for residual acid mist and chlorine, with nitrogen oxide abatement added where nitrate-based pre-treatment is also operated
Emission and effluent control	Headspace under negative pressure, scrubber liquor analysed and logged, wash water and spent liquor neutralised and settled with the hydroxide sludge returned for metal recovery
Instrumentation and control	PLC with touch-screen interface controlling the rectifier, circulation, heating, dosing and filtration, monitoring cell voltage, cell current and busbar temperature, running a staged automatic cycle with a manual mode, and logging the parameter record per campaign
Alarm and interlock schedule	Defined alarm list with set points and trip actions covering over-voltage, over-current, busbar over-temperature, electrolyte over-temperature, loss of circulation, low level and loss of extraction
Campaign records	Feed assay, electrolyte assay, slime assay, product assay, parameter log, closed metal balance, certificate of analysis and a retained reference sample filed against one campaign number
Final purity, standard release	Au ≥ 99.99%, released against a fire-assay determination with an ICP-OES cross-check and accompanied by a certificate of analysis
Final purity, second campaign	99.999% gold produced by charging first-pass gold as the anode of a second campaign
Gold recovery	At least 99% of the gold charged taken into the cathode product and the declared side streams under the design window, with the balance recovered from the anodic residue, the residual plate and the electrolyte bleed rather than written off
Metal loss	Below 0.02% of the gold charged, achieved by the sealed headspace and the condenser
Anode slime	Silver chloride and PGM residue retained in the anode bag, washed, dried, weighed and declared by metal content before leaving the machine
Residual anode handling	Spent plate, hanger residues and cell-bottom material returned to the melting station and cast into fresh anodes rather than sold as scrap
Product forms	Fine gold ingot, button or granule; cathode gold crystal; silver chloride slime; PGM-bearing anode slime; residual anode remelt stock; electrolyte bleed solution; rebuilt electrolyte; recovered fume condensate
Quality verification	Fire assay with an ICP-OES cross-check on the product; gold, free acid, silver and base metal determination on the electrolyte; ICP-OES on the anode, the slime and the effluent; deposit weight reconciled against ampere-hours and anode consumption
Acceptance testing	Production trial on the customer’s own anode material, confirmed against measured gold recovery into the cathode, the released product assay and the declared slime content, with a performance certificate issued
Documentation	Process design package with the rated output basis and mass balance, site interface schedule, operating procedures, alarm schedule, electrical drawings, equipment layout, spare parts catalogue, campaign record template and certificate of analysis
Footprint and layout	Cell size, harvesting station and service clearances engineered to your building, its floor loading and the access required for anode handling, with the figure stated in the process design package
Site services and utilities	Rectifier rating, circulating pump duty, condenser duty, hood exhaust volume, cooling water, compressed air, drainage and effluent interim storage listed item by item in the site interface schedule with a value against each line
Materials of construction, summary	Polypropylene and PPH with an anti-ageing additive, titanium-clad copper, titanium, acid-resistant bag and membrane polymer, PP and PVDF wetted parts, transparent polymer for the hood panel
Consumables and replacement	Anode bags, filter elements, gaskets and seals, pump and dosing parts and rectifier components carry a stated replacement interval and a recommended on-site stock list issued at handover

Technical Advantages

The rating is defined, so quotations become comparable. Because the rated output is stated as fine gold deposited on the cathode, a buyer can compare two machines on the same basis. Read a feed-weight rating as if it were a product rating and the same cell looks roughly a third larger; read an anode-consumption rating as a product rating and it counts metal that never leaves the machine. Result: a quotation that can be audited line by line instead of a number that depends on which definition the supplier had in mind.
The site interface is a schedule with values, not a paragraph of warnings. Nine services are listed item by item — electrical supply and rectifier rating, circulating pump duty, condenser duty, hood exhaust volume and negative pressure, cooling water, compressed air, floor loading and electrode access, drainage and containment, and effluent interim storage — each engineered to your assay and output. Result: the builder can price and prepare the site before the machine ships, instead of the plant discovering a missing service during commissioning.
The machine’s cycle is one programme on one panel. Ramp, deposition, harvest, wash, dry, weigh, cast and reset run as a staged automatic sequence with a manual mode reserved for anode inspection and for intervention. Result: campaign behaviour is reproducible across operators and across shifts, and the process does not depend on which shift is on duty.
Admission is gated on assay, not on sales enthusiasm. The feed survey establishes gold, silver, copper and platinum group metal figures before a machine is specified, the silver and copper ceilings are stated as numbers, and a lot above them is routed to parting first. Result: no customer is sold a cell that will passivate in the middle of a plate and hand back residual gold that has to be remelted.
The silver problem is answered four ways at once. An anode ceiling fixed in process design, upstream parting where the feed exceeds it, a superimposed alternating component that sheds the chloride film continuously, and anode bagging that retains the detached chloride at the plate face. Result: an anode that dissolves to completion instead of stalling, and a by-product that leaves as a declared, saleable material rather than as waste.
Metal loss is contained by equipment rather than by care. The machine runs hot because the chemistry requires it, a hot chloride electrolyte evaporates, and the sealed headspace and condenser return that vapour to the cell. Result: loss below 0.02% of the gold charged, checked against the campaign mass balance rather than asserted.
The deposit is reconciled inside the campaign. Weighing the dried deposit against the ampere-hours passed and the anode weight consumed is a check the machine performs on itself, and it separates three causes that look identical from the outside — current lost to water decomposition, an unnoticed contact resistance, and gold that has gone into the electrolyte. Result: a deviation is diagnosed at the machine rather than discovered at the assay bench after the metal has been cast.
The working inventory is designed down and stated. The electrolyte must carry gold to conduct the plating reaction, so cell volume converts directly into metal held as solution; volume, geometry, circulation and bleed schedule are set as design outputs with the resulting figure declared. Result: less capital tied up in gold that is neither feedstock nor product, which is the largest recurring cost of ownership in this process.
Routine inspection is scheduled against the silver figure. The anode is lifted and cleaned on an interval derived from the feed assay rather than when output appears to fall. Result: film is cleared before it stalls dissolution, and the interval is a documented instruction rather than an operator’s judgement.
The power supply is built for where it has to live. Rectifier, superposition unit and control gear sit in an enclosed compartment separated from the acid vapour that fills a refining room, and the supply is interlocked to stop the machine on an abnormal reading. Result: a power supply whose service life is set by its components rather than by its environment, and a fault that halts a campaign instead of quietly spoiling one.
Every campaign carries its own record. Feed assay, electrolyte assay, slime assay, product assay, parameter log, closed metal balance, certificate of analysis and a retained reference sample are filed against one campaign number. Result: a recovery or grade question can be answered from the record for that lot, and the customer’s own laboratory can check the same retained sample.
Release is by assay, and disagreement is expected. The lot is certificated only when a fire assay with an ICP-OES cross-check confirms the specified grade. Result: a product claim that a buyer, an exchange or a tolling counterparty can verify independently rather than take on trust.
Capacity grows on a validated machine. Cell capacity, cathode area and rectifier rating are modular, and the extension is planned against services that were sized for it at the outset. Result: the first machine proves the route on the customer’s own material instead of becoming stranded capital.
Consumables are scheduled rather than discovered. Anode bags, filter elements, gaskets and seals, pump and dosing parts and rectifier components carry a replacement interval and a recommended on-site stock list issued at handover. Result: the machine is not idle waiting for a part that nobody knew it needed.
Running cost is given as a structure you can price locally. The levers are named in the order they matter — the gold held in the electrolyte, then power, then acid and consumables, then labour — and the cost is priced per project against your own tariff and wage rate. Result: a total cost of ownership the customer can compute rather than a per-gram figure lifted from someone else’s cost base.
The economic floor is stated openly. The size below which a refining cell cannot carry its own working inventory, supervision and floor space is disclosed, together with the alternatives that suit small volumes better. Result: qualified enquiries, and customers who are not sold a machine that should not have been sold.
The melting, sampling and assay stages are inside the scope. The customer’s output is a certificated ingot with a fire-assay determination, an ICP-OES cross-check and a retained sample. Result: a saleable product at the machine’s discharge rather than an intermediate that has to be discounted.
The machine closes the gold loop without breaking the circuits around it. Gold from solution-side recovery, cementation or ion exchange feeds in as anode stock, silver chloride slime leaves for the silver circuit and the PGM fraction leaves for the PGM line. Result: one machine that sits inside a flowsheet instead of at the end of one.

Service Process

Step 1 — Anode data and duty review. You provide the anode material type, an assay or typical analysis with the silver and copper figures, the expected monthly gold volume, the shift pattern and any site constraints on power, water, floor loading or space. We state at this stage whether the material can be run directly or needs parting, drying or consolidation first, and whether the volume is above the economic floor for a refining cell. Output: preliminary route statement, boundary conditions and a clear scope of supply.

Step 2 — Machine configuration and rated output proposal. The cell size, cathode area, electrode count, rectifier rating, electrolyte volume, circulation and temperature duty, headspace exhaust volume, condenser duty and the harvest and casting arrangement are calculated from your assay and your target output, and the rated output basis is written down with them. Output: a configuration proposal with the rated output basis stated, plus the draft site interface schedule.

Step 3 — Laboratory and pilot validation on your material. A representative sample is cast to a small anode and run through a full cycle at bench scale, establishing the anode silver tolerance, the achievable current density, the electrolyte window, the expected deposit grade, the campaign time and the slime yield on real material rather than on assumption. Output: a test report with the product sample returned for your own assay.

Step 4 — Module fabrication and factory function test. Cell, frame, electrode assemblies, busbar set, power and control cabinet, electrolyte circuit, headspace, condenser and scrubber are fabricated, assembled and function-tested before shipment, with material certificates and test records retained and issued with the machine. Loose and bulk items are packed for sea or land freight with the preservation that hot chloride duty requires. Output: a factory function test record and the shipping documentation set.

Step 5 — Site interface schedule and building preparation. The nine services on the interface schedule are confirmed against your building, together with foundations, floor finish, containment and drainage, electrode handling access, the exhaust route to atmosphere and the effluent interim storage. Output: a signed interface schedule, layout drawing and utility connection drawing your builder can work from.

Step 6 — Installation, pressure test and electrical checkout. Our engineers supervise setting the modules, aligning the frame and cell, assembling the electrode and busbar set, leak and pressure testing the electrolyte circuit, commissioning the headspace and ducting under negative pressure, and checking out the electrical and control installation against the drawings. Output: a mechanically complete machine ready for electrolyte charging.

Step 7 — Electrolyte charging and machine commissioning. The electrolyte is made up to the working tenor and free acid band, charged, brought to temperature and circulated; the current programme and the superimposed alternating component are set from the route sheet; and a water and dummy campaign is run to confirm the interlocks, the alarm responses and the extraction before any gold is charged. Output: a commissioned machine with its setpoints recorded against the configuration document.

Step 8 — Operator training and production qualification. Training covers safe handling of chlor-auric acid, hydrochloric acid and acid mist, anode inspection and cleaning, deposit quality judgement, electrolyte sampling and assay practice, slime handling, harvest and casting, alarm response and routine maintenance, taught on the actual machine. The first production campaign then runs on your own anode and the agreement is confirmed against measured recovery, product assay and slime content. Output: trained operators, a signed SOP set and a performance test certificate with the first certificate of analysis.

Step 9 — Consumables, spares and continuing process support. The spares stock list and replacement intervals are handed over with the machine, spare parts are supplied at cost, and our engineers stay available for process troubleshooting and for re-specifying the current programme and electrolyte window as your feed mix changes. Output: continuing production support with a stocked spares position and revised procedures as the feed changes.

Warranty And After-Sales Service

Warranty period. Twelve months from successful commissioning or eighteen months from shipment, whichever falls earlier, covering design, manufacture and assembly defects of the supplied equipment. Excluded: consumables such as anode bags, filter elements, gaskets, seals and reagents, and damage from misuse or from anode material outside the agreed specification.
Performance commitment. Where the anode material matches the tested sample, we stand behind the gold recovery into the cathode, the released product assay and the anode silver tolerance established in the process design package, with the production trial as the reference point. Output: a documented performance acceptance attached to the machine’s file.
Spare parts. Wear and critical spares — anode bags, cathode plates or seed sheets, hangers, gaskets, seals, pump and dosing parts, filter elements and rectifier components — are quoted at the time of order and held available afterwards, with a recommended on-site stock list issued at handover. Output: an on-site spares position agreed before the machine enters production.
Remote support. Telephone, email and messaging support on operating questions, alarm interpretation, cell voltage diagnosis and electrolyte chemistry, whenever the machine is running. Output: same-day response on operating issues.
On-site service. Engineer attendance for warranty faults, process problems and periodical check-ups, with response and attendance times agreed in the contract according to your location. Output: on-site intervention and a service report.
Operator retraining and refresher visits. Additional training, refresher sessions and process optimisation visits as your feed mix, anode quality or product standard changes, including re-establishing the current programme and the electrolyte window after a change of anode supplier. Output: updated training and revised procedure documents.
Capacity extension support. Engineering advice and supply for extending a validated machine — additional cells, larger cathode area, higher rectifier rating — against the service capacity identified when the site interface schedule was first issued. Output: an extension designed against services that already exist.
Documentation set. Operation and maintenance manuals, the process design package with the rated output basis and mass balance, the site interface schedule, process flow diagram, piping and instrumentation diagram, equipment layout, electrical drawings, alarm schedule, spare parts catalogue, safety data for the reagents handled and the emergency response plan. Output: complete documentation handover at commissioning.
Compliance support. Assistance with emission and effluent parameter declarations, condenser and scrubber performance verification, and the handling, storage and disposal requirements for chlor-auric acid, hydrochloric acid and the slime streams. Output: technical data for your permit applications.
Lifetime technical support. The process design remains yours, and our engineering team remains available for modification and expansion advice for the operating life of the machine. Output: long-term engineering continuity.

Frequently Asked Questions

What does the capacity rating of a gold electrolysis machine actually measure?

Fine gold deposited on the cathode — the refined product, weighed after washing and drying, and reconciled against the ampere-hours passed. A rating expressed on feed weight counts the silver and copper that leave the machine as slime and as electrolyte, so the same cell can appear roughly a third larger for the same output; a rating expressed on anode consumption counts metal that partly returns to the melt as residual plate. Whenever you compare two machines, establish which of the three the figure refers to, because the three are not interchangeable and the difference is the most common reason two quotations for the same duty come back far apart. On this machine the basis is fine gold deposited, and it is written into the process design package so the figure can be audited rather than accepted.

What is the smallest gold electrolysis machine that still makes commercial sense?

The limit is not the cell, it is everything the cell carries with it: the gold held in the electrolyte as working inventory, the supervision a cycle of 10–20 h requires, and the floor space, power and services the machine occupies whether it runs or not. Below a certain daily output those items cannot be carried by the margin on the metal, and that is the point at which a refining cell stops being the right answer. For small volumes the honest routes are a toll-refining arrangement with a refinery that runs a machine properly, or a solution-side recovery circuit if the gold is still in a liquor. This page states the boundary rather than selling a machine into it, because a machine that should not have been sold is a machine that will not be reordered.

Which feed materials should not be charged to a gold electrolysis machine?

Low-grade ore, un-stripped electronic scrap, plating rinse waters and dilute liquors. An electrolytic refining cell dissolves a solid anode, so it needs a plate that is mostly gold: ore and raw scrap must be concentrated mechanically and pyrometallurgically first, and rinse waters and dilute liquors belong on a solution-side recovery circuit where the metal is recovered from solution rather than purified from a plate. Within the anode family the material also has to clear the composition gate — above 6% silver or above 2% copper in the anode, the lot is parted before it is cast, because silver chloride film stalls dissolution and copper above the working limit reports to the cathode and costs grade.

What happens to the machine when the anode runs high in silver?

Silver in the anode is oxidised at the anode face and precipitates immediately as silver chloride, which is essentially insoluble in the chloride electrolyte; the film coats the plate, the effective anode area falls, the local current density on the remaining exposed metal rises, cell voltage climbs and dissolution finally stalls with a substantial fraction of the gold still inside the plate. Three things hold it in check: the superimposed alternating component of the power supply sheds the film continuously, the anode bag retains the detached chloride so it cannot reach the cathode, and the operator lifts the plate on the schedule the silver figure dictates and brushes the accumulation clear. What none of those do is remove the ceiling — above roughly 6% silver in the anode the lot is parted before casting, and the machine is quoted for the material that comes out of that step.

Which site services have to be sized before the machine is ordered?

Nine of them, each listed with a value in the site interface schedule: the electrical supply and the rectifier rating; the circulating pump duty; the condenser duty; the hood exhaust volume and its negative pressure requirement; cooling water flow and temperature where the duty needs it; compressed air; floor loading and access for anode and cathode handling; drainage and containment capacity; and the interim storage volume for effluent and bleed. These are the items that decide whether a machine can be installed on a given floor, and they are the most common cause of a commissioning delay when they are discovered after the order rather than before it. They are engineered to your anode assay and target daily output, then stated as figures you can hand to your own builder.

What does one operator do across a full machine cycle?

The panel runs the staged programme, so the operator supervises rather than drives it. Across a cycle the work is to register the lot and confirm the machine is configured for that anode; check plate geometry, cast weight and immersion depth; verify the charged electrolyte and free acid against the make-up record; confirm the current programme, the superimposed alternating component and the per-cathode current after start-up; lift and inspect the anode on the interval the silver load sets and brush any accumulated chloride clear; sample the electrolyte so the bleed is taken on the assay; draw the cathode, wash it and return the wash water to the circuit; dry, weigh and reconcile the deposit against the ampere-hours passed; open the bags, draw the slime, change the filters and top up the level; and cast, sample and release the ingot before resetting the machine for the next lot.

What sets the length of one machine campaign?

Two things: the thickness of the anode plate and the current programme the lot is given. A campaign runs 10–20 h of machine time. A thicker plate holds more metal and takes longer to dissolve at a given current; a higher current dissolves it faster but is only available to a plate whose silver content will tolerate it, because the chloride film builds faster as the current rises and the anode, not the rectifier, is the constraint. The programme is therefore written per lot from the anode assay at the configuration stage and confirmed on the production trial, rather than fixed at purchase.

What does the machine arrive with, and what is built on site?

The machine arrives as function-tested modules with material certificates: cell and frame, electrode assemblies and busbar set, the rectifier and control cabinet, the electrolyte circuit, the sealed headspace with condenser and scrubber, and the harvest, casting and sampling station where those are in scope. What is built on site is the foundation and floor finish, the electrical supply to the machine terminals, the cooling water and compressed air connections, the drainage and containment, the exhaust route to atmosphere, and the effluent interim storage. Installation, leak and pressure testing of the electrolyte circuit, electrical and control checkout and the commissioning run are supervised by our engineers, and the site interface schedule issued with the quotation is the document the builder works from.

How is the machine’s output sampled and assayed before a lot is released?

The deposit is dried to constant weight and weighed, then reconciled against the ampere-hours passed and the anode weight consumed before it is allowed to move to the melt. The dried gold is melted under flux, sampled from the melt rather than from the surface of the ingot, and cast; the cast product is analysed by fire assay with an ICP-OES cross-check, and the lot is released only when the analysis confirms the specified grade. Anode, electrolyte and slime are assayed under the same campaign number, the mass balance is closed, and a retained reference sample is held for the warranty period so the customer’s own laboratory can run the same sample and disagree if it wishes.

What drives the running cost of a gold electrolysis machine?

Four things, in the order they matter. First the gold tied up in the electrolyte as working inventory, because that is a recurring capital cost rather than a consumable. Second power, set by the cell voltage window, the current programme and the duty the machine runs, and the reason voltage is treated as a symptom rather than as a throttle. Third acid and consumables: electrolyte make-up, anode bags, filter elements, gaskets and the flux used in casting. Fourth labour, which across a cycle of 10–20 h with one operator per machine is modest compared with a chemical route. We quote the structure and the levers per project against your own power tariff and labour rate rather than publishing a per-gram figure borrowed from somebody else’s cost base.

Can a gold electrolysis machine be extended later, or is capacity fixed at purchase?

It can be extended. Cell capacity, cathode area and rectifier rating are modular, so a machine that proves the route on your own material can be grown as your volume grows rather than replaced, and additional rectifier headroom can be added as the current density is increased. What cannot be retrofitted cheaply is the building: the services and the floor are sized once, so the site interface schedule is written with the practical extension in mind and the spare capacity you will need at the next step is identified at the quotation stage. That way the entry machine is a first stage rather than stranded capital.

What alarms and interlocks does the machine carry?

A defined alarm list with set points and trip actions, covering over-voltage, over-current, busbar over-temperature, electrolyte over-temperature, loss of circulation, low level and loss of extraction. An abnormal reading trips the rectifier rather than allowing a campaign to continue to the end of a bad lot, and the event is written into the campaign parameter log with the time and the reading that caused it, so the cause can be traced afterwards to the electrode contact, the electrolyte or the power supply. Alongside the trips, the panel logs cell voltage, cell current, busbar temperature and electrolyte temperature continuously, which is what makes a campaign reproducible rather than a matter of operator recollection.