Chromate coating of zinc surfaces
AssigneeNihon Parkerizing Co., Ltd.
InventorsKenshi Saeki, Kazuyuki Ohyama, Iwao Kawasaki
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Abstract
A chromate composition and process provide improved corrosion resistance and paint adhesion for zinc surfaces. The aqueous acidic composition contains hexavalent and trivalent chromium phosphate and fluorozirconate at prescribed concentrations. The composition is applied and dried without rinsing to yield a chromium coating weight of 10-200 mg/m.sup.2.
Claims8
An aqueous acidic chromate coating composition for steel sheets which have a zinc based plating comprising 10-100 grams/liter of chromic acid, 1-21 grams/liter of trivalent chromium ion, 0.1-4 grams/liter of phosphate ion and 0.1-4 grams of fluorozirconate ion and that the solution is prepared in such a way that in the said acidic aqueous solution the ratio by weight of hexavalent chromium trivalent chromium is from 1.5/1 to 5/1, the ratio by weight of chromic acid/fluorozirconate ion is from 5/1 to 100/1 and the ratio by weight of the phosphate ion/fluorozirconate ion is from 1/2 to 2/1.
Dependencies are inferred from the claim text.