Chemistry: electrical and wave energy – Processes and products
Patent
1988-07-12
1989-08-29
Niebling, John F.
Chemistry: electrical and wave energy
Processes and products
204 376, 204 58, C25D 1108, C25D 1118
Patent
active
048614408
ABSTRACT:
A process for making an improved composite aluminum article having an intermediate layer of porous coarsely crystalline aluminum oxide integral with the aluminum substrate. The oxide is electrolytically formed by applying a voltage which is steadily and continuously increased from start to finish of the electrolysis from about 5-15 volts to about 65-85 volts at a rate of about 1-3 volts/minute and utilizing a current density which is increased from start to finish of the electolysis from about 10-30 amps/sq. ft. to about 60-80 amps/sq. ft. at a rate of about 1-3 amps/sq. ft./minute. A preferred electrolyte bath comprises about 15-20 oz./gal. 66 degrees Baume sulfuric acid, about 2-3 oz./gal. malonic acid, about 2-4 oz./gal. oxalic acid, about 0.5-1 lb./gal. carbon powder, and about 2-4 oz./gal. sucrose. The crystal lattice of the aluminum oxide layer is saturated with a salt of a divalent or trivalent metal which forms a complex with the aluminum oxide of enhanced strength, hardness and corrosion resistance. A low friction material for enhancing the appearance and function of the treated aluminum article may be applied thereto. Before the aluminum oxide layer is saturated with the salt, it is dehydrated to render it hygroscopic.
REFERENCES:
patent: 4128461 (1978-12-01), Lerner et al.
patent: 4193848 (1980-03-01), Severns-Lanbenteid
patent: 4413049 (1983-11-01), Beaudet
Frederick A. Lowenheim, Electroplating, McGraw-Hill Book Co., 1978, pp. 452-467.
Leader William T.
Niebling John F.
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