Corrosion behavior of lithium silicate-based Zn-5.5Al-4.5Mg-0.3Ce coating

The effects of Ce on the microstructure of Zn-5.5Al-4.5Mg alloy and the corrosion mechanism of Zn-5.5Al-4.5Mg-0.3Ce alloy and its coatings were investigated in this research. The results show that the structure of Zn-5.5Al-4.5Mg-0.3Ce alloy is composed of hcp-Zn, fcc-Al and ternary eutectic structure (Zn/Al/MgZn2/Mg2Zn11), without dendritic tissue and MgZn2. The salt spray corrosion performance of Zn-5.5Al-4.5Mg-0.5CMC-2C coating was significantly better than that of Zn-5.5Al-4.5Mg-0.3Ce coating and Zn-5.5Al-4.5Mg-0.5CMC coating. The corrosion current density of Zn-5.5Al-4.5Mg-0.5CMC-2C coating was 3.217 mu A cm(-2), which was significantly lower than 3.96 mu A cm(-2) of Zn-5.5Al-4.5Mg-0.3Ce alloy and 5.879 mu A cm(-2) of Zn-5.5Al-4.5Mg alloy. Sodium carboxymethylcellulose and graphene improve the film formation and electrical conductivity of water-based lithium silicate resin. During corrosion of Zn-5.5Al-4.5Mg-0.3 Ce series alloy and coatings, Zn and Mg2Zn11 dissolved preferentially to form corrosion products of Zn-5(OH)(6)(CO3)(2) and Zn-5(OH)(8)Cl2H2O. Mg6Al2(OH)(16)CO(3)4H(2)O and Zn4Al2(OH)(12)CO(3)3H(2)O bimetallic hydroxide colloidal membranes were formed, which attached and wrapped on the surface of early corrosion products. Mg6Al2(OH)(16)CO(3)4H(2)O and Zn4Al2(OH)(12)CO(3)3H(2)O, preventing the dissolution of soluble corrosion products, improved the corrosion resistance of Zn-5.5Al-4.5Mg-0.3Ce alloy.