Trivalent chromium passivate process

Details Trivalent chromium passivate process Trivalent chromium passivate process

1981-06-15

1983-01-04

Silverberg, Sam

Metal treatment

Compositions

Heat treating

148 621, C23F 700

Patent

active

043670997

ABSTRACT:
A process for treating metal surfaces, particularly zinc and zinc alloy surfaces, for depositing a passivate film of improved corrosion resistance and hardness which comprises the steps of providing an aqueous acidic solution containing effective amounts of chromium ions substantially all of which are in the trivalent state, hydrogen ions to provide a pH of about 1.2 to about 2.5, an oxidizing agent, and at least one additional metal ion selected from the group consisting of iron, cobalt, nickel, molybdenum, manganese, aluminum, lanthanum, cerium, lanthanide mixtures as well as mixtures thereof, contacting the substrate with said aqueous acid solution for a period of time sufficient to form a passivate film thereon, preferably water rinsing the passivated substrate, thereafter contacting the passivated substrate with a dilute aqueous rinse solution for a period of at least one second containing a bath compatible water soluble inorganic and/or organic silicate compound present in an amount effective to impart improved corrosion resistance and hardness to the passivate film, and drying the silicate rinsed substrate.

REFERENCES:
patent: 2548420 (1951-04-01), Chester et al.
patent: 3368928 (1968-02-01), Chadha et al.
patent: 3687740 (1972-08-01), Pearlstein et al.
patent: 3932198 (1976-01-01), Schneider
patent: 4171231 (1979-10-01), Bishop et al.

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