Research on Zinc-Silica Composite Plating

Abstract

In order to explore a new kind of high anti-corrosion and environmentally benign materials to protect steel, zinc-silica composite coatings were prepared by plating technique. In this paper, experiments on electrodeposited zinc-silica composite coatings are reported, effects of cathodic current density, agitation, additive, anode number, space between anode and cathode on the appearance of coatings are discussed, composition and property of zinc-silica composite coatings are investigated. The electrolyte composition and operating conditions are: ZnCl2 80 g/L, KCl 220 g/L, additive 10 ml/L, SiO2 2~3 g/L, pH 4~5, current density 140~180 A/m2, temperature 15~35°C, 20~30 cm space between anodes and cathodes, once plating time is 60 min.The content of silica in coatings is 0.47~0.56%(mass), the thickness of coatings is 20~23 μm, and the time of composite coatings appearing red rust in neutral salt spray test(NSS) keeps more than 410 h. During the experiment lasting for 30 days, pH value and composition of the electrolyte and deposition speed of coatings all keep relatively stable. Further more, this composite plating technique can reach the first National Entironment Standard(GB 8978–1996). All the results show that zinc-silica composite coatings with no chromate treatment have better corrosion resistance than zinc coatings, stability of this composite plating technique is satisfactory, maintenance operation is convenient, and the plating process is innocuous and safe, so this technique will undoubtedly has a great future in application.