Enamel coating for protection of the 316 stainless steel against tribo-corrosion in molten zinc alloy at 460 °C

Abstract

Hot-dip galvanizing provides excellent corrosion and wear resistance for steels. However, the equipment itself, such as the steel roller, immerged in corrosive molten zinc suffers serious material loss during steel’s production. Its protection has become the main technique problem in modern galvanizing line. In this study, an enamel coating was designed and prepared. Its tribo-corrosion in molten zinc alloy (Zn-0.2 wt% Al) at 460 °C was investigated in comparison with the traditional WC-12Co composite coating and the 316 stainless steel. Results indicate that the steel suffers serious material damage. Various corrosion products of Fe2Al5Znx form at the worn surface and the wear scar has reached 200 μm deep after merely 5 h tribo-corrosion. Though the two coatings provide an improved tribo-corrosion resistance, for the WC-12Co coating, its chemical reaction with the molten zinc increases brittleness and promotes cracking. The synergistic wear and corrosion cause its degradation. The enamel coating performs better during tribo-corrosion. It is chemically stable in molten zinc thus able to provide high corrosion resistance. In addition, the amorphous [SiO4] network and the self-lubricating CaF2 crystallite help it to build up an intact amorphous glaze layer readily at surface on sliding, leading to a reduced wear loss. During the whole tribo-corrosion process, the enamel coating is completely free of cracking, and the Zn penetration is inhibited.