The technique of covering the surface of a cheaper material with thin layer of gold. There are a number of different ways of gilding metal and non-metallic objects (see below)
Acid
Cold Mercury Gilding
Depletion Gilding
Diffusion bonding
Electrochemical
Fire
Also known as mercury gilding
Foil gilding
Fusion
A process used in ancient South America, especially Ecquador, for the gilding of copper alloys by dipping or fusion of molten gold alloys to the surface, resulting in thick gold alloy coatings. May also be used to create silver alloy coatings over copper.
This is the precious metal version of hot-dip plating which has a wider range of applications.
Lacquer
Leaf gilding
Mercury or fire gilding

The art of applying a thin layer of gold leaf or dust to a surface using chemical or mechanical processes for the purpose of decoration.