Below is a list of Acid Etching manufacturers from Azusa, California. Acid etching, otherwise known as chemical milling or chemical etching, is a chemical process used by many industrial metal parts manufacturers to etch, cut or engrave very delicate or precise lines into metal. This process involves very little mechanical work, for it is an almost entirely chemical procedure. Almost every type of metal can be chemically etched, including most types of steel, titanium, brass, nickel, copper and so forth.