| Galvanizing on steel surface is one of the effective means of improving theservice life of steel. Chromate conversion treatment on galvanized steel, not onlyenhances its decorative properties, but also improves its corrosion resistance. However,due to the highly toxic carcinogenic hexavalent chromium causing serious damage tohuman health and the environment, this technology has been restricted and prohibited.Therefore, more environmentally friendly and effective chromium-free conversionprocess is urgently needed.Due to poor corrosion resistance of single vanadate conversion coating ongalvanized steel surface, the effect of different conversion solution consisting ofvanadate combining with potassium, sodium, magnesium, aluminum and ammoniumfluorosilicate respectively was studied by single factor experimenta method. Theresults showed that, under the condition of3.5g/L ammonium metavanadate?20g/L ammonium fluorosilicate, pH2,23min and25?, the obtained conversioncoating was continuous and uniform and its corrosion resistance was the best?itsneutral salt spray test was up to72h. The results from scanning electron microscopy(SEM), EDS analysis and electrochemical test demonstrated that the colorfulamorphous structure conversion coating was made of50.42%Zn?23.32%O?18.91%V?7.35%Si, and its corrosion potential was68mV more positively than that beforeconversion. The corrosion resistance of galvanized steel was improved effectively. |
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