Patent ID: 6149795
Filing Date: 2000-11-21
Classification: C25D

Abstract:
An improved method of anodizing an aluminum or aluminum alloy workpiece and concurrently inhibiting the growth of fungus without hindering the effectiveness of the anodizing process, comprising the steps of:(a) providing an aqueous anodizing bath consisting essentially by weight of about 3 to 5 percent sulfuric acid, from about 0.5 to 1 percent boric acid, not more than about 5.0 g/L aluminum ion, not more than about 0.2 percent chloride ion, and a fungistat consisting of benzoic acid, a water-soluble salt of benzoic acid selected from the group consisting of sodium benzoate, potassium benzoate, or lithium benzoate, or mixtures thereof, said fungistat having a concentration in the range of about one part per million (1 ppm) to about ten thousand parts per million (10,000 ppm) by weight;(b) maintaining said bath at a temperature from about 70 to about 90 degrees F.;(c) immersing said workpiece in said bath;(d) ramping the voltage applied across said workpiece in said bath from about 5 to about 20 volts such that the current density is substantially uniform across the workpiece and the average current density does not exceed about 10 amperes per square foot; and(e) maintaining said workpiece in said bath for a time such that an adherent coating of aluminum oxide is applied thereto having a coating weight between about 200 and 600 milligrams per square foot.