Processes for improving the corrosion resistance of ni-co-metal coatings containing boron
United States Patent 3247028

The corrosion resistance of chemically deposited metal coatings containing boron and nickel and/or cobalt is improved by treating the coated surface with an aqueous solution of a hexavalent chromium compound. The chromium compound is preferably chromic acid or potassium dichromate in a concentration of 1-300 g/l. CrO3 and the solution may also contain 0.1-2% of phosphoric acid, the treatment of the coated surface being effected at 18 DEG C.-100 DEG C. In the examples given an iron plate is coated with a 90-92% Ni and 8-10% B layer by treating with a solution containing 30 g/l. nickel chloride, 40 g/l. sodium hydroxide, 50 g/l. ethylene diamine, 0.6 g/l. sodium borohydride, 1 g/l. thiodiglycollic acid and 10 mg/l. lead chloride. Iron plates are also coated with a 47% Co. 51% Ni, 2% B layer by treating with a solution containing nickel and cobalt chlorides, ammonium chloride, sodium acetate, thiodiglycollic acid and N-diethylborozane in methanol.

Heinz-gunter, Klein
Eberhard, Zirngiebl
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C01B35/04; C23C18/34; C23C18/48; C23C18/50; C23C22/24; C23C22/33
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