Differential growth of active-driven LDHs in different zones (weld zone/base material zone) of friction stir welding and corrosion protection

The paper studied, for the first time, the kinetics and protective effect of layered double hydroxides (LDHs) film formation on the base material and welded zones of a friction stir-welded (FSW) ZK60 Mg alloy. Under various time gradients, the LDHs film was successfully grown in-situ in the weld zone area. The weld zone surface’s corrosion resistance and film formation behavior were examined both longitudinally and transversely. According to the research, as the growth period grows, the form and composition of the in-situ generated LDHs films on the welding area's surface will progressively alter. The LDHs film on the welding zone’s surface gets denser and more homogeneous after 12 h of growth, which effectively lessens the contact between the substrate and the corrosive media and increases corrosion resistance. Additionally, the differential growth behavior of LDHs films grown in situ on the weld zone and the base zone was investigated in conjunction with the SVET. The unique microstructure formed during the FSW process serves as an optimization driving factor for the growth of LDHs, providing a new mechanism perspective for understanding the corrosion protection of lightweight welded structures.