| Abstract Zinc-Chromium chemical conversion film, called Dacromet in foreign country, has high corrosion resistance as well as no hydrogen brittle, no pollution, high temperature resistance, good combination with steel base and the organic coat, uniformity, and etc. so it is used widely. The production, performance, structure and composition of the film were investigated in this article systematically and gain some senseful results. 1. Technological parameters of Zinc-Chromium film are the Zinc powder 262 to 299g/l, Aluminum powder 38 to 43g/l, Cr03 24 to 36g/l, succinic acid 8 to 12g/l, baking temperature 25O~?2OC, baking time 15 to 40mm. The best of them is the Zinc powder 320g/1, Aluminum powder 40g/1, Cr03 32g/l, succinic acid lOg/i, baking temperature 300C, baking time 20mm. 2. Film structure, phrase composition, element composition were detailedly studied using XRD, SEM, EPMA, EDS and XPS. There are lots of Zinc and Aluminum powders in the film, which are combined by oxide. the combination between film and base steel also depend on oxide, the structures have efficient protection to steel base. There is still about 0.51 %(Element weight) of hexavalent Chromium in the film. 3. The film structure was analysesed, results show Zinc-Chromium film is the whole passivation of Zn, Al and the base steel. The theory of film formation and mechanism of corrosion resistance are explained successfully. 4. Comparison between Zinc-Chromium film and Zinc plating was made. It is shown Zinc-Chromium film is much better than Zinc plating on corrosion resistance, so Zinc-Chromium film can substitute Zinc plating in much case.
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