Chromate-plating bath and process for finishing zinc zinc alloy or cadmium surfaces
AssigneeAtotech Deutschland GmbH
InventorEliane Jeannier
Life of this patent
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Abstract
Process for finishing zinc, zinc alloy or cadmium surfaces which consists in bringing the components to be treated into contact first with an acidic chromate-plating bath based on chromium, cobalt and silver salts and then with a top coat bath comprising a colloidal silica, a corrosion inhibitor, a complexing agent, a surfactant and a black dye.
Claims9
Chromate-plating bath, consisting essentially of an aqueous solution having a pH of between 1 and 2 and containing, per liter, 5 to 40 g of hexavalent chromium ions, 5 to 20 g of sulphate ions, 0.1 to 0.3 g of cobalt ions, 0.1 to 0.65 g of silver ions and 50 to 150 ml of at least one organic acid.
Chromate-plating bath consisting of an aqueous solution having a pH of between 1.2 and 1.8 and containing per liter 7-15 g of hexavalent chromium ions, 7-12 g of sulphate ions, 0.1 to 0.2 g of cobalt ions, 0.15-0.3 g of silver ions and 70-120 ml of a organic acid wherein zinc, zinc alloy or cadmium surfaces are finished with a deep, glossy and uniform color and having substantial corrosion resistance, resistant to thermal shock showing substantially no white rust nor red rust after exposure to salt spray for at least 200 hours.
Dependencies are inferred from the claim text.