In the earlier processes of galvanising iron and steel the zinc was deposited upon the metal by electrolysis, but the hot-bath process in most galvanising establishments has entirely superseded the electro process. In the so-called galvanising process, the iron is first immersed in hydrochloric acid to render it perfectly clear and free from scale. It is then immersed in molten zinc, the surface of the molten metal being kept covered with powdered sal-ammoniac, this salt possessing the property of dissolving the oxide from the surface of the molten zinc, and also aiding the adhesion of the molten zinc to the iron surface. If the iron has a slight coating of tin. and is then coated with zinc, the zinc coating is said to adhere more firmly and does not scale when the metal is being worked.