Galvanization, named after the Italian scientist Luigi Galvani, was originally the administration of electric shocks (in the 19th century also termed Faradism, after Michael Faraday). It stemmed from Galvani's induction of twitches in severed frogs' legs, by his accidental generation of electricity (see galvanism). This archaic sense is the origin of the meaning of galvanized when meaning 'stirred to sudden action'.
Later the word was used for processes of electrodeposition. Nowadays it typically means hot-dip galvanizing, a chemical process that is used to coat steel or iron with zinc. This is done to reduce corrosion (specifically rusting) of the ferrous item. The zinc coating prevents oxidation of the protected metal by forming a barrier. Zinc oxide is a fine white dust that (in contrast to iron oxide) does not cause a breakdown of the substrate's surface integrity as it is formed. Indeed the zinc oxide, if undisturbed, can act as a barrier to further oxidation, in a way similar to the protection afforded to aluminium and stainless steels by their oxide layers. Hot dip galvanizing deposits a thick, robust layer that may be more than is necessary for the protection of the underlying metal in some applications. This is the case in automobile bodies, where additional rust proofing paint will be applied. Here, a thiner form of galvanizing is applied by electroplating, called "electro-galvanized". Where the metal is not to be painted or is to be used in critical exposure conditions such as near salt water, "hot-dip galvanized" is preferred for its long term durability. Galvanized nails are now usually electro-galvinized but these are greatly inferior to the hot dipped kind, particularly when used in fences.
Galvanic or sacrificial-anode protection uses ingots of zinc electrically bonded to the metal it is to protect where the metals will be subject to an electrolytic solution. In such a solution the zinc is absorbed into the electrolyte in preference to the metal that it protects.
Obviously in some environments both mechanisms can be at work. For example, the traditional measure of a coating's effectiveness is resistance to a salt spray . Galvanization cannot protect surfaces subject to surface abrasion.