Hot Dipped Zn-Al-Mg-Cu Coating with Improved Mechanical and Anticorrosion Properties

wt.%Mg-0.1 wt.%Cu (ZAM) were deposited by hot dipping method on mild steel substrates. The phase structure, cross section microstructure, composition, microhardness and corrosion property of the coatings were characterized by X-ray diffraction (XRD), environmental scanning electron microscopy (ESEM-EDS), microhardness test, and electrochemical analysis. Continues salt spray tests were performed to access the corrosion behaviour of coatings. The microhardness of ZAM coating was improved to 178 HV comparing with 43 HV of G coating and 89 HV of ZA coating. The improved microhardness of ZAM coating is due to the strengthening effect of grain boundary at which intermetallic compounds of Al5Fe2Zn0.4, MgZn2 and Mg2Zn11 has precipitated. ZAM coating also showed the highest impedance and the extended exposure during the salt spray test. Simonkolleite was identified as the main corrosion product on three tested coatings. The slow corrosion mechanism of ZAM coating was discussed