iron alloyed superficially with zinc, by plunging the metal, previously well cleaned by friction with dilute acid, into a bath of melted zinc covered with sal ammoniac, and stirring it about for some time. When iron thus treated is exposed to humidity, the zinc is said to become oxidized in consequence of galvanic action. This coating protects the iron beneath from rusting; and hence galvanized iron will retain its whiteness for a long period under circumstances that would cause ordinary tinned iron to exhibit marks of corrosion.