Mcgean-rohco, Inc.

Billie J Page

George S Bokisa

Craig V Bishop

Marlinda J Thomay

A method is described for preparing a black chromium-containing conversion coating on a zinc-nickel alloy surface containing at least about 8% nickel in the alloy or on a zinc-iron alloy surface. The method of the invention comprises contacting said surfaces with an aqueous acidic solution comprising trivalent chromium and an amount of a phosphorus acid selected from phosphoric acid, phosphorous acid, hypophosphorous acid, and mixtures thereof effective to provide a solution having a pH of from about 1.0 to about 2.5. Metal articles having zinc-nickel alloy surfaces containing at least about 8 % nickel in the alloy or having zinc-iron alloy surfaces which have been treated in accordance with the method of the invention exhibit the desired blackened surfaces and are characterized by improved corrosion resistance.

Black chromium-containing conversion coatings on zinc-nickel and

It now has been found that a smooth, level, matte and/or bright deposit of tin, lead or tin-lead alloy can be deposited on a substrate from an aqueous plating bath which comprises

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Cleveland Hts., OH, United States of America

Billie J Page