Abstract: An electrolytic bath for coating articles of magnesium and its alloys consists essentially of an aqueous solution containing an alkali metal silicate (e.g., potassium silicate), an alkali metal hydroxide (e.g., potassium hydroxide) and a fluoride (e.g., hydrofluoric acid). In the process, the magnesium article is immersed in the bath and an electrical potential is applied between the magnesium article serving as the anode, and a cathode immersed in the bath until a visible spark is discharged on the surface of the metal. The potential difference is maintained for a few minutes until the desired coating thickness is formed.

Abstract: To produce a corrosion-resistant coating thereon which is hard and uniform and capable of withstanding the action of strong acids and alkalis, a body of magnesium metal or an alloy of magnesium is first treated with an aqueous solution of hydrofluoric acid to form a fluoromagnesium layer on the metal surface. The coated metal is then immersed in an electrolyte bath comprising an aqueous solution of alkali metal silicate, and an aqueous solution of an alkali metal hydroxide. An electrical potential is applied between the magnesium metal anode and a cathode (iron or nickel) in the bath until a visible spark is discharged on the surface of the metal. The potential difference is maintained for a few minutes until a uniform silicate layer is formed on the fluoromagnesium layer.