hydroxide; filtering and washing the pre- cipitate; adding water to the filtered and washed precipitate to form a sludge having a solids content from 15 to 50%; and ap- plying the sludge as a patination agent to a surface of the copper bearing material, and wherein the method includes storing the sludge at a temperature below 5°C until just before the final step.

Coat ing M e t h o d u.s. Patent 5,691,002. Nov. 25, 1997 H. Oda eta/., assignors to Kansai Paint Co. Ltd., Amagasaki, Japan

A coating method comprising sequen- tially applying an amine-neutralized aque- ous intermediate coating composition and an amine-neutralized aqueous topcoating composition.

Elect ro less Gold Plat ing Process U.S. Patent 5,691,003. Nov. 25, 1997 T. Sone and H. Wachi, assignors to Electroplating Engineers of Japan Ltd., Tokyo

A plating method by means of an elec- troless gold plating solution comprising filling a tank with electroless gold plating solution for plating parts positioned in the tank; injecting air over a wide enough area at the bottom of the tank for forming air bubbles that rise uniformly where the parts are positioned for surrounding with air bubbles; maintaining a plating temperature substantially higher than the storage tem- perature of the electroless gold plating so- lution for periods of time between plating operations; and adjusting the flow rate of injected air at a given plating temperature, while maintaining substantially uniform plating.

Dual -Coated Metal Subst ra tes u.s. Patent 5,691,048. Nov. 25, 1997 O.E. Roberto and M.A. Maxim, assignors to Henke/ Corp., Plymouth Meeting, Pa.

A method for coating a metal substrate, comprising applying a first liquid coating composition comprising an intimate mix- ture of a hexavalent chromium-providing substance, supplied by 80 to 100% chromic acid and providing above 5 but below 100

g/L of chromium, expressed as CrO3; above 50 but below 500 g/L of liquid me- dium of pulverulent metal selected from the group consisting of zinc, aluminum, mixtures thereof, and alloys of same; be- low 50% by volume but substantially above about 15% of water-soluble organic liquid substance from the group consisting of tri- and tetra-ethylene glycol, di- and tri-propylene glycol, and the water-soluble C~-C 4 ethers of all such glycols, diacetone alcohol, the water soluble Cr-C 4 ethers of diethylene glycol, and mixtures of the fore- going; and above 0.0005% by volume of dispersing agent; heating the substrate to convert the liquid coating formed to an adherent, water-insoluble first solid coating on the substrate; applying a second liquid coating of an acidic aqueous composition comprising dispersed resin solids and an activator, which acidic aqueous composi- tion forms on a metallic surface a resinous coating that increases in thickness the longer the surface is contacted with the composition, to form an uncured autode- posited second liquid coating over the first solid coating; and curing to form an au-

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170 METAL FINISHING • JUNE 1998