Benzothiazole-assisted in-situ growth of protective LDH coating on Zn-Al-Mg coated steel surface in NaCl solution

Zn-Al-Mg coated steel (ZM-steel) has emerged as a preferred material in automotive and infrastructure applications, yet its long-term durability remains challenged by localized corrosion in chloride-rich environments. Herein, a sustainable and scalable corrosion protection strategy based on the in-situ formation of layered double hydroxide (LDH) films intercalated with benzothiazole (BTZ) was reported. By exploiting the controlled corrosion of ZM-steel surface in BTZ-containing NaCl solution, compact LDH architectures spontaneously formed, incorporating BTZ molecules within their interlayers. The resulting hybrid coating integrated the physical barrier effect of LDH with the release of BTZ anions, enabling interfacial passivation and sustained corrosion inhibition. Comparative electrochemical tests revealed that BTZ-containing NaCl solution yielded markedly enhanced corrosion-resistance as compared to NaCl solution or bare BTZ solution, with charge transfer resistance increasing from 9.44 × 10 2 to 9.13 × 10 4 Ω·cm 2 . Moreover, epoxy-overcoating effectively suppressed filiform corrosion (FFC) of ZM-steel substrate for over 35 days. Unlike conventional hydrothermal or carbonate-assisted routes for LDH fabrication, this precursor-free strategy proceeds under ambient conditions without additional reagents, underscoring its simplicity, efficiency, and scalability. These findings demonstrate that the moderate corrosion is beneficial to the formation of LDH on ZM-steel surface.