It is not often that it is necessary to coat either brass or copper with zinc, the ordinary "silvering" (i. e., washing with tin) answering most effectually under all ordinary circumstances. Still, a method of coating them with zinc may be found useful. The usual process of boiling the brass or copper articles in a concentrated solution of ammonium chloride containing shavings of zinc is superseded by a method in which an alkaline solution of zinc oxide is found to give a better result in less time. An excess of powdered zinc is placed in a boiling solution of potash or caustic soda. The brass or copper articles after cleaning are then immersed in the solution, and after a minute's immersion they may be withdrawn covered with a coat of zinc. By this process an easy method of converting copper plates into pinchbeck is furnished to the mechanic. The copper plates thinly coated with zinc are heated, preferably in an oil bath, to 250°-285° F., when the coating of zinc will be found to combine with the copper, forming an excellent pinchbeck, more or legs of a golden colour, When the desired hue is attained, the plates must be immediately cooled in water or any other suitable liquid.
The process is also employed for making Zamboni's piles (dry voltaic piles). Very thin pieces of sheet copper are coated with zinc, and the latter is subsequently removed from one side of the copper by means of hydrochloric acid. Piles made from discs of the metals thus prepared are said to give much better results (are more active electromotors) than layers of gold leaf or the other materials used in constructing Zamboni piles.