Enhanced Corrosion and Wear Resistance of AZ91 Magnesium Alloy by Fabrication of Galvanized Zn-Al-Mg Coating in Chloride Solution

Due to the poor surface properties of the magnesium alloys, a protective Zn-Al-Mg coating with Ni/Cu interlayer was developed on AZ91 magnesium alloy by simple hot-dipping method in this paper. Microstructure of the coated AZ91 magnesium alloy was observed using scanning electron microscope (SEM), optical microscope (OM). The corrosion resistance and wear resistance of the Zn-Al-Mg coating and the magnesium alloy were comparatively investigated by potentiodynamic polarization testing, electrochemical impedance spectroscopy (EIS), friction and wear testing. Results revealed that a dense and uniform Zn-Al-Mg coating, which had a thickness of more than 100 ??m, was coated on the magnesium alloy surface. Moreover, the bond between the galvanized Zn-Al-Mg coating and the magnesium alloy substrate was metallurgical, and the hot dipping process had almost no influence on the microstructure of the magnesium alloy. Electrochemical tests in NaCl solution indicated that the corrosion resistance of the coated magnesium alloy had been significantly increased. Further to this, the micro-hardness and wear resistance of the coated magnesium alloy surface were also significantly increased. In addition, the galvanic corrosion between the galvanized Zn-Al-Mg coating and the magnesium alloy was also investigated and discussed.

Automated summary

In this paper, a protective Zn-Al-Mg coating with Ni/Cu interlayer was developed on AZ91 magnesium alloy by simple hot-dipping method. The research showed that this coating significantly improved the corrosion resistance and wear resistance of the magnesium alloy.