Abstract: The present invention relates an aqueous composition and process for electro-depositing at a pH of about 1 to 3.5, a ductile, highly adhesive, adsorptive and absorptive zinc coating on a metal article. The article with the electro-deposited zinc coating can be subjected to further treatment, such as, a second functional or decorative coating or painting and forming. The ductile zinc coating is resistant to cracking during forming and metal articles treated in accordance to the present invention, including the formed areas, are highly resistant to corrosion, stress corrosion cracking, wear and galling.

Abstract: The present invention provides an aqueous composition and process for the electrodeposition of a layer of zinc containing silicon and phosphorus on a metal substrate. The electrodeposition composition is prepared by reacting metallic silicon and zinc with phosphoric acid and an alkali metal hydroxide in the ratio of between 0.4 and 1.3 moles of alkali metal hydroxide per mole of phosphoric acid, and adjusting the solution to a pH of 2 or higher after completion of the reaction. The coating is deposited on the metal substrate by electrodeposition and comprises about 70% to about 99.5% by weight of zinc, and about 0.10% to about 10% by weight of silicon, and about 0.5% to about 20% by weight of phosphorus.The resultant zinc/silicon/phosphorus coating improves the resistance of the metal substrate to corrosion, wear, galling and stress corrosion cracking.