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: A multi-layer plating and method for improving the corrosion resistance of ferrous metal articles, such as steel fasteners, are provided in accordance with the invention. The multi-layer plating comprises, in sequence over a ferrous metal substrate, a layer of an alloy which has micro-throwing power, such as nickel-cadmium, nickel-zinc, iron-cadmium, iron-zinc, cobalt-cadmium, or cobalt-zinc, a layer of cadmium, cadmium-tin alloy, a dual layer of cadmium and tin, zinc or zinc alloy, a layer of copper, a layer of nickel, and a layer of chromium or a metallic chromium substitute. The method comprises plating, and preferably electroplating, the aforementioned layers of alloy and metals over an article having a ferrous metal substrate to obtain improved corrosion resistance.