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Electroplating Jewellery

by Chris Corti
In this paper, we shall concentrate on the electroplating of gold and gold alloys and
rhodium – one of the platinum group of metals with a good white colour and tarnish
resistance – for decorative applications.
Electroplating is a method to put a metal coating onto an object, in our case a piece of
jewellery, by placing it in a solution containing the metal to be plated and passing an
electrical current through the piece and the solution. It is possible to electroplate coatings
of most pure metals and even some alloys.
Electroplating is a comparatively quick and easy process to carry out and does not require
major investment in costly equipment. It can be done successfully with very simple, basic
equipment. Finished carat gold jewellery may be electroplated with gold for several
reasons:
1. electroplating carat gold jewellery with pure 24ct gold to impart a richer gold
colour.
2. electroplating with carat or pure gold to give a more uniform colour, hiding
variations in colour of the component parts and solder lines.
3. electroplating to give a different desired colour; a wide range of colour can be
achieved by co-depositing gold with other metals.
4. electroplating to hide surface defects or to improve properties. In addition, there
are other uses for gold electroplating, viz:
5. electroplating base metal or silver items with gold to obtain a gold appearance as
in fashion jewellery and gilt silver.
Rhodium is often used to give a good white colour to white gold jewellery (which is often
not a good white colour) or is used selectively on yellow gold jewellery to give local areas
of whiteness, often around gem stone settings, and also to plate the master model made
in silver used for making the rubber mould in investment casting.
In contrast, electropolishing is the opposite to electroplating: we remove metal from the
surface of our jewellery by passing an electrical current in the opposite direction and, if
we get the conditions right, we can do this in a way that leaves a polished surface. Many
jewellery producers use electropolishing as part of their total finishing process in gold
jewellery manufacture. In this paper we shall discuss the following aspects:
 Basic principles
 Factors in electroplating to be considered
 Surface preparation in electroplating
 Safety and pollution aspects
 Gold plating – caratage, colour, types of electrolytes and deposits
 Rhodium plating baths
 Equipment
 Electropolishing of gold jewellery – types of electrolytes
Much of this information is contained in our two WGC publications – The Technical
Manual and the Finishing Handbook.