Microstructure and Corrosion Resistance of Zn-Mg Alloy Coating Prepared by Mechanical Energy Aided Diffusing Method

Zn-Mg alloy coating was prepared on railway gasket by means of mechanical energy aided diffusing method. The surface and cross section morphology, phase composition and corrosion resistance of the permeable layer in neutral salt spray environment were analyzed by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectroscopy (EDS) and weight loss method. The results showed that Zn-Mg alloy coating was compact and uniform. With the salt spray corrosion time extending from 120 h to 2 000 h, the white corrosion products on the surface of Zn-Mg alloy coating gradually increased, but no red corrosion products appearred. After 2 000 h salt spray corrosion, the mass loss of Zn-Mg alloy coating sample was 0.048 4 g/(m²· h), which indicated that Zn-Mg alloy coating sample had good corrosion resistance. The Zn-Mg alloy coating was mainly composed of FeZn_10.98, FeZn_6.67, MgZn₂, Mg₂Zn₁₁ and Mg₄Zn₇ alloy phases. The MgZn₂ and Mg₂Zn₁₁ formed by the infiltration of magnesium element were the main reason for the relatively good corrosion resistance of Zn-Mg alloy coating.