Abstract
A method and a treatment solution for post-treatment of an article with a metallic surface, where the metallic surface is made of one or more metals of a standard oxidation potential within the range -2.5 to +0.5 V. A thin coating is formed on the metallic surface by a treatment with an aqueous solution containing a molybdenum compound selected among molybdic acid and salts thereof in a concentration of 2.9 to 9.8 g/l calculated as molybdenum, as well as a compound capable of forming a heteropolymolybdate, such as phosphoric acid, together with a molybdate. The treatment is performed under conditions where the metal surface is maintained at a potential within the range of -600 and -1800 mV/nhe. A corrosion-protecting and/or decorative effect is obtained which can be compared with the effect obtained by conventional chromate treatment, and which avoids the environmental and toxicologic drawbacks associated with the chromate treatment.
Original language | English |
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Patent number | WO/1993/010278 |
Filing date | 27/05/1993 |
Country/Territory | International Bureau of the World Intellectual Property Organization (WIPO) |
Publication status | Published - 1993 |