Study of the physicomechanical and corrosion properties of hot-dip zinc coatings on the construction profiles

To assess the quality hot-dip zinc coating on steel construction, microhardness, porosity and adhesion strength of the coating to the substrate were investigated. It was shown that these properties of zinc coatings depend on the phase composition, which in turn are determined by the content of silicon in the steel. Studies have shownthat all types of zinc coatings can be classified as non-porous, because porosity does not exceed 6%. Pores are localized mainly in ζ-phase. The most dense coatings with a minimum pore size formed at low silicate steel (0.027% Si) at standard temperature and after high temperature hot-dip galvanizing of high-silicon steel (0.767% Si). The microhardness of the iron-zinc coating depends on the lattice structure and porosity of phases. δ-phase has a maximum hardness (HV 80). The porous ζ-phase has minimum micro-hardness (20-45 HV). The corrosion resistance of zinc coating in different electrolytes and the nature of the corrosion destruction with different chemical composition were analyzed. Analysis of the standard electrochemical potential of zinc coatings on various steels has shown that the most corrosive environment for zinc coatings are fluorides. The research allowed us to evaluate the service life of the steel construction in real-world conditions.