The effect of ZnAl-LDHs-CO3 on the corrosion behaviour of Zn-5Al alloys in 3.5wt.% NaCl solution

Highlights: • The ZnAl-LDHs−CO₃ is prepared on Zn-5Al alloy using the substrate as an internal source of the both metal ions. • The ZnAl-LDHs−CO₃ nanosheets on the Zn/Al eutectoid area are denser than that on the Zn/Al eutectic area. • ZnAl-LDHs−CO₃ nanosheets will prevent the generation of cracks in the corrosion product film. • ZnAl-LDHs−CO₃ can restrain the corrosion of Zn-5Al alloy substrate. In this work, the ZnAl-LDHs−CO₃ film was prepared on Zn-5Al alloy by in-situ growth method. The ZnAl-LDHs−CO₃ nanosheets on the Zn/Al eutectoid areas are denser than that on the Zn/Al eutectic areas of Zn-5Al alloy. During the immersion corrosion process, the corrosion products of LDHs/Zn-5Al deposit in the gaps of the ZnAl-LDHs−CO₃ film, which will form a dense film on the Zn-5Al alloys. The electrochemical analysis shows that the ZnAl-LDHs−CO₃ film can restrain the corrosion of Zn-5Al alloy substrate. At last, the corrosion protection mechanism of ZnAl-LDHs−CO₃ film on Zn-5Al alloys are discussed in detail.