What electroplating is

At the start of this lesson we mentioned using electrolysis to gold-plate jewellery. Think also of the many things used as ornaments at home.

Many items — gold- or silver-coloured flower vases, trays and similar ware — owe their shine to a thin layer of metal that has been coated onto them.

The metals usually used for plating are ones of low activity, such as tin, copper, silver and chromium. The plating metal must have some special property that the surface being plated does not.

Why plate instead of making it solid

A spoon of solid silver or a car bumper of solid chromium would be very expensive, and chromium is too brittle to shape. Plating gives the best of both: a strong, cheap metal such as steel inside, with a layer only a fraction of a millimetre thick of the metal whose property we want on the outside. The layer must cover the surface completely, though. As you will see at the end of the chapter, a scratch through a plating of a less reactive metal can make the iron beneath rust faster, not slower.