Abstract: Method for coating a rectifier metal (aluminum) with alkali metal molybdenate/alkali metal silicate or alkali metal tungstenate/alkali metal silicate comprises immersing a rectifier metal (anode) and a cathodic metal in an electrolytic solution and imposing voltage potential between the two electrodes. The voltage is first raised to about 240 to about 260 volts during an oxidation stage, and thereafter to about 380-420 volts to form the desired coating.Unique electrolytic solutions are provided for the electrodeposition method.

Abstract: A method is provided for electrolytic coating of a rectifier metal with a hard, adherent, uniform and corrosion-resistant coating which predominates in vanadium oxides. A rectifier metal (anode) and a metal cathode are immersed in the electrolytic bath and voltage potential is applied across the two electrodes and raised to about 280 volts within about 25 to about 35 seconds, and thereafter raised further therefrom to between about 280 and about 360 volts within a few minutes until the desired coating thickness is obtained. The electrolytic bath comprises a mixture of a major amount of alkali metal orthovanadate and a minor amount of alkali metal silicate in water.

Abstract: An electrolytic bath for coating articles of aluminum and its alloys consists essentially of an aqueous solution containing an alkali metal silicate, a peroxide, a water-soluble carboxylic group-containing organic acid and a water-soluble fluoride. A vanadium compound may also be included in the bath whenever the coated articles are intended to be used for decorative purposes. In the process, the aluminum article is immersed in the bath and a voltage shock is applied thereto by imposing a voltage potential between the aluminum metal serving as the anode and a cathode immersed in the bath. The voltage potential is quickly raised to about 300 volts within about 2 to about 10 seconds and thereafter, the voltage is increased gradually to about 450 volts within a few minutes until the desired coating thickness is formed.

Abstract: A relatively low voltage process for electrolytically coating a rectifier metal with a hard, glassy, corrosion-resistant silicate coating. The rectifier metal is immersed in an aqueous solution of pure potassium silicate (or a mixture of potassium silicate and a peroxide, e.g., sodium peroxide) and a voltage potential is applied between said metal and a cathode which is also immersed in said solution until a visible spark is discharged at the surface of the rectifier metal. The voltage potential is then increased to about 300 volts and maintained at that level until the desired thickness of the coating is deposited.