A plating tank is the container that holds the electrolyte solution used in electroplating jewellery with gold, rhodium, palladium, or other metals. The tank houses the anode — the source of metal ions — and the cathode workpiece, with the electrolyte conducting current between them under the regulated DC of a plating rectifier. Tank construction, capacity, and the chemistry of the bath inside it govern what the rectifier and the operator can achieve at the bench.

Materials and construction

Plating tanks for jewellery use are typically built from borosilicate glass, polypropylene, or stainless steel. Glass is favoured for small benchtop baths because it permits visual monitoring of the work and is inert to most plating chemistries. Polypropylene is preferred for larger tanks and for solutions that attack glass over time. Stainless steel tanks are used for some industrial processes where the tank wall doubles as part of the electrical circuit, but they require careful chemistry selection because the tank is itself in contact with the bath.

Volume ranges from a few hundred millilitres for pen-plating reservoirs to tens of litres for production tanks. Heating elements, agitation systems, and filtration are added as the chemistry requires.

Bath chemistry and temperature

Different plating chemistries operate at different temperatures and require correspondingly different tank features. Rhodium baths run hot, typically at 40 to 50 degrees Celsius, requiring a heated, well-ventilated tank because the sulphuric-acid-based electrolyte produces aggressive vapour. Gold baths — cyanide-based or sulphite-based — operate at room temperature or modestly elevated temperatures and have less demanding ventilation requirements. Each bath has a specified pH window and a minimum bath turnover before the chemistry must be refreshed.

Tank life and bath life are linked. Contamination from the workpiece, base-metal dissolution, and chemistry drift all shorten the useful life of a bath and require either replacement or adjustment.

In the trade

For repair benches running rhodium and gold plating in low volume, a few small dedicated tanks of the appropriate chemistry are the working setup. Production shops run dedicated lines with larger tanks, automated dosing, and effluent treatment. The overall quality of the plating depends on the combination of clean tank, fresh bath, stable rectifier, and correctly prepared workpiece — failures in any one of these compromise the result.

Further reading

• GIA — bench finishing and plating practice
• International Gem Society — electroplating fundamentals
• AGTA — trade practice and bench equipment