Influence of silicon coating on the corrosion resistance of Zn-Al-Mg-RE-Si alloy

The electric arc spraying method was used to prepare the Zn-Al-Mg-RE-Si alloy coating with different content of silicon. The corrosion resisting property was measured by copper accelerated salt spray (CASS) and corrosion weightless test. The influence of silicon content on the corrosion resisting property was investigated by XRD, SEM, polarization curve and electrochemical impedance spectroscopy (EIS) and the electrochemical property of coating in the corrosion process was analyzed. The results showed that the density of coating was improved significantly since the major nonequilibrium glass-like state phase was composed of silicon and other metals existed in the Zn-Al-Mg-RE-Si alloy coating, which prevented the corrosive medium and retarded the corrosion velocity because of compact corrosion products in the corrosion embryo. The Zn-Al-Mg-RE-Si coating had better corrosion resistance than the Zn-Al-Mg-RE because of more positive potential, half corrosion current density and double electrochemical reaction resistance.