Corrosion Resistance of Electroplated Zn-Ni Alloy Coating on 300M Ultra-High Strength Steel

Zn-Ni alloy coating was prepared on 300M ultra-high strength steel by electroplating in Cd-free and cyanide-free environmentally friendly bath of chloride-sulfate. The effects of plating parameters on the appearance and adhesion strength of the alloy coating, and the relationships among Ni content and microstructure and corrosion resistance of the coatings were investigated using bending test, scanning electron microscopic analysis, energy dispersive spectrometric analysis, neutral-salt-spray test, X-ray diffraction, and electrochemical polarization test. It was found that current density had obvious effect on the composition of the Zn-Ni alloy coating, the unpassivated alloy coating had better anti-corrosion ability than porous electroplated Cd coating. Moreover, the alloy coating containing 13.5% Ni had the highest enduration of 1 632 h to neutral salt spray test, indicating that the Zn-Ni alloy coating has good corrosion resistance.