Phase Equilibrium Of Zn-Co-Ni-Sb Quaternary System And Synergistic Action Of Co,Ni And Sb On Galvanized Coating

Hot-dip galvanizing process is simple and effective,and the excellent corrosion resistance,compactness and adhesion of the coating make hot-dip galvanizing technology has unique advantages in the field of metal corrosion prevention.But in the silicon steel hot-dip galvanizing often occurs"Sandelin effect",the coating performance is gray and too thick growth,which seriously affects the appearance and quality of galvanized products.At present,multi-alloy zinc bath technology is an effective method.Adding antimony to the zinc bath will enhance the fluidity of the zinc bath and bring beautiful zinc flowers on the surface of the plating parts,but it can not solve the adverse consequences of sundelin effect in hot dip galvanizing.In order to get the hot dip galvanizing products with good coating texture and beautiful appearance,it needs the synergistic action of a variety of elements to achieve it,and the two elements of cobalt and nickel have a very obvious inhibitory effect on the silicon reactivity of silicon containing steel.In this paper,the effect of the phase equilibrium diagram of Zn-Co-Ni-Sb quaternary system（93at.%Zn）and the synergistic effect between cobalt,nickel and antimony on the microstructure of Q235 steel hot dip alloy coating was studied,and a kind of alloy zinc bath with superior comprehensive properties was sought.In this work,the equilibrium alloy method was adopted to study the Zn-Co-Ni-Sb quaternary system（93at.%Zn）isothermal cross section at 450℃/600℃by SEM,SEM-EDS and X-ray diffractometer.The results show that:At 450℃,there exists one four-phase equilibrium region and three three-phase equilibrium region.The solubility of Sb inγphase is not more than 1.5 at.%,Sb is almost insoluble inγ₂ phase,and Co is almost insoluble in Sb₂Zn₃phase.There is only one three-phase equilibrium region and two two-phase equilibrium regions at 600℃.The solubility of Sb atγ₁ is 0.1at.%.The influence of alloy elements Co,Ni and Sb on the microstructure of the alloy layer and the synergistic effect of Co-Sb and Co-Ni-Sb on the microstructure of the alloy layer were studied by hot-dip galvanizing experiment.The corrosion resistance and mechanical properties of the coating were evaluated.The results showed that:Adding a small amount of Sb to the zinc bath has no effect on the alloy layer of Q235 steel coating.Adding a certain concentration of Ni or Co can thin the coating.Adding Co in the Zn-0.05wt.%Sb zinc bath can reduce the thickness of the alloy layer,but the microstructure of the alloy phase layer is still silicon reactive.The addition of 0.1-0.4wt.%Ni in Zn-0.05wt.%Sb-0.08wt.%Co zinc bath can effectively inhibit the silicon reactivity of Q235 steel,and the thickness of alloy layer is obviously reduced.When the content of Ni is higher than 0.1wt.%,the growth mode of alloy layer is mainly determined by diffusion reaction.The corrosion resistance of Co-Ni-Sb zinc bath and Co-Ni-Sb zinc bath were both improved,and the corrosion resistance of Co-Ni-Sb zinc bath was obviously improved.The hardness of Co-Sb and Co-Ni-Sb zinc bath plating is higher than that of pure zinc bath plating,and the zinc bath composition with the highest hardness is 0.1wt.%Ni+0.08wt.%Co+0.05wt.%Sb.