The process of depositing a layer of a desired metal on another material by means of electricity is called:

Electroplating is the process of coating an object with a thin layer of a metal using electric current. It is based on the chemical effect of electric current, that is, electrolysis.

How electroplating works:

• The object to be plated is made the cathode (negative electrode).
• A plate of the metal to be deposited is made the anode (positive electrode).
• Both are dipped in an electrolyte, a solution of a salt of the metal to be deposited.

When a direct current (DC) is passed, metal ions from the solution move to the cathode and are deposited on the object as a thin, even layer. At the same time, metal from the anode dissolves into the solution, keeping the concentration of metal ions constant.

For example, to copper-plate an iron key, the key is made the cathode, a copper plate is made the anode, and a solution of copper sulphate is used as the electrolyte.

Uses of electroplating:

Chromium plating on car parts, bicycle handlebars, bath taps and kitchen fittings gives a shiny surface that resists corrosion and scratches. Chromium is usually plated over a layer of nickel.

Silver and gold plating on cheaper metals makes jewellery and cutlery that look like silver or gold, at low cost.

The laws of electrolysis were given by Michael Faraday in 1833-34. The waste from electroplating factories contains toxic chemicals and must be disposed of carefully.

Why not the other options?

• ✗Galvanisation is the coating of iron or steel with zinc, usually by dipping it in molten zinc, not mainly by electricity.
• ✗Anodising thickens the natural oxide layer on aluminium.
• ✗Electrolysis of water splits water into hydrogen and oxygen.