This specification applies to electro-deposited coatings of zinc on iron and steel, except for the following: coatings applied to components having threads of basic major diameter from 0.050 to 0.500 inch; coatings applied to sheet, strip, and wire in the unfabricated form; coatings applied to high chromium alloy steel. Provision is made for five classes of ordinary zinc coating, each corresponding to a specified thickness, and for passivated zinc coatings.