Effect of vanadium content on the microstructure and properties of hot-dip galvanized Zn-0.05%Ni-V alloy coating

Zn–0.05%Ni–V alloy coatings were hot-dip galvanized on the steel containing 0.09% Si by adding a small amount of V to a Zn–0.05%Ni bath. The effect of V content on microstructure of the coatings was studied. The resistance of the pure Zn, Zn–0.05%Ni, and Zn–0.05%Ni–V coatings to corrosion and oxidation was studied by electrochemical impedance spectroscopy, electrochemical polarization and high-temperature oxidation experiments. The results showed that the addition of more than 0.03% (mass fraction) V to the Zn–0.05%Ni bath effectively restrain the Fe–Zn reaction and the growth of ζ phase in coating. As compared with pure Zn and Zn–0.05%Ni coatings, the Zn–0.05%Ni–V coating has better corrosion resistance in 5% NaCl solution based on their larger electrochemical impedance, more positive self-corrosion potential, enhanced polarization resistance, and lowered corrosion current density, as well as better high-temperature oxidation resistance. The coating containing 0.05% V has the highest oxidation resistance due to the formation of more compact oxidation product on its surface.