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Basic Principles of Electroplating

& Electropolishing

Electroplating and electropolishing is carried out in an electrolytic cell, Fig.1. This
comprises two electrodes that are electrically connected and immersed in a solution –
called an electrolyte. When an electrical current is passed through the cell, metal
dissolved in the electrolyte is deposited on the negative electrode – the Cathode – whilst
the metal of the positive electrode – the Anode – may be removed and dissolved in the
electrolyte. Thus, metal passes from the anode into solution in the electrolyte and is then
deposited on the cathode.

Figure 1 – Schematic: electrochemical plating cell
Thus, if we make the cathode the piece of jewellery we wish to plate and the electrolyte
contains gold, then we can deposit gold on our jewellery item. On the other hand, if we
make our piece of jewellery the anode in a suitable electrolyte capable of dissolving gold,
then, under the right electrical conditions, we can remove the surface selectively to obtain
a polished surface. A typical electrolytic cell is shown in Fig. 2 and can enable several
pieces to be electroplated simultaneously.

Figure 2 – Typical electroplating bath