PLATING

coating a metal or other material such as plastic or china with a hard, nonporous metallic surface to improve durability and beauty. Such surfaces as gold, silver, stainless steel, palladium, copper, and nickel are formed by dipping an object into a solution containing the desired surface material, which is deposited by chemical or electrochemical action. While much plating is done for decorative purposes, still more is done to increase the durability and corrosion-resistance of softer materials. Most automotive parts, appliances, housewares and flatware, hardware, plumbing and electronic equipment, wire goods, aircraft and aerospace products, and machine tools are plated for durability. Several processes are used for plating: electroplating, electroless plating, and anodizing are the major processes used today, but other methods also have been developed. In electroplating (q.v.), the article to be plated serves as the cathode in an electrolytic bath composed of a solution of the salt of the metal to be deposited. The other terminal, the anode, may be of the same metal or another chemically unaffected conductor. A low-voltage current is passed through the solution and causes the metal in solution to plate the article. Electroless plating (q.v.) relies on reactions in a chemical bath that may or may not be aqueous and may or may not be heated. Anodizing (q.v.) is similar to electroplating, but the article to be plated serves as the anode in the electrical circuit.