CeO2 modified SiO2 acted as additive in electrodeposition of Zn-Ni alloy coating with enhanced corrosion resistance

Recently, rare earth oxide has attracted much attention because of its widely applications in petroleum, chemical engineering, metallurgy, ceramics etc. Among them, ceria has been considered as an important additive to improve metal's corrosion resistance. In this study, CeO2 modified SiO2 was prepared as additive in electrodeposition of Zn-Ni coating. The state of the as-prepared particles was characterized. The structure and wettability as well as the microhardness of coatings were tested. Moreover, the corrosion performance of coatings was analyzed in detail by means of potentiodynamic polarization technique and electrochemical impedance spectrum (EIS) in 3.5 wt % NaCl solution which used as corrosion medium. The results show that the particles disperse well among the coatings. The morphology of the coating presents a dense structure and keeps a highly preferred orientation. Meanwhile, the coating with CeO2 modified SiO2 exhibits much better corrosion resistance properties compared with that of both Zn-Ni and Zn-Ni-SiO2 coatings. The corrosion current density of the prepared coating was remarkably decreased with two and one orders of magnitude compared with those two CeO2-free coatings mentioned above, respectively. The introduction of CeO2 also significantly increases the coating's electrochemical impedance. The corrosion mechanism of the above three types of coating on low carbon steel were analyzed and discussed based on two different equivalent circuit models respectively.