Abstract: Novel micro-throwing alloy undercoatings, multi-layer coatings containing a novel micro-throwing alloy undercoating and method of improving the corrosion resistance of ferrous metal articles are provided in accordance with the invention. The novel micro-throwing alloy undercoatings are applied as an initial layer over ferrous metal and comprise a layer of alloy having micro-throwing power, such as nickel-cadmium, nickel-zinc, iron-cadmium, iron-zinc, cobalt-cadmium, cobalt-zinc or a ternary or quaternary alloy containing iron, nickel or cobalt in combination with cadmium or zinc. The method comprises application, preferably by electroplating, of a layer of novel micro-throwing alloy undercoating directly over ferrous metal, optionally followed by one or more layers of metallic or organic coatings which further contribute to improved corrosion resistance.

Abstract: The present invention provides a method of improving the corrosion resistance of a ferrous metal substrate by providing a non-ferrous corrosion resistant plated undercoating by steps of sequentially plating onto the substrate a first layer of copper of about 0.00015 to 0.0005 inches in thickness, a layer of zinc of about 0.0002 to 0.0005 inches in thickness and a second layer of copper of about 0.00015 to 0.0005 inches in thickness and, optionally, multiples of such zinc and copper layers, and thereafter subjecting the plated substrate to a thermal treatment sufficient to effect partial diffusion at the respective interfaces of each of the layers of copper and zinc to provide zones of non-homogeneous copper-zinc alloy of infinitely variable linear distribution of copper and zinc.