In-situ grown Mg-Fe-inhibitor-LDH conversion film on steel for improving corrosion protection in the chloride contaminated environment

Use of layered double hydroxide (LDH) conversion films is an effective method for enhancing the corrosion protection of metals, which has been extensively studied on non-ferrous metals. Steel, being the most commonly used engineering material , would significantly benefit from such technology if LDH films could be formed on its surface. In this study, an Mg-Fe-pAB-LDH conversion film is successfully grown in situ on Cr-alloy steel. The properties of the Mg-Fe-pAB-LDH film and its precursor Mg-Fe-CO 3 -LDH film are characterized using SEM, XRD , EDS , XPS , and electrochemical methods . The results show that both LDH films are composed of cross-linked blade-like flakes oriented perpendicular to the substrate, with numerous intersecting voids. The incorporation of pAB − inhibitor ions and CaCO 3 by-products into LDH film significantly improves its corrosion resistance in chloride-contaminated environments. The inhibition efficiencies of the Mg-Fe-pAB-LDH film in 0.1, 0.3, and 0.6 mol/L NaCl solutions are 99 %, 97 %, and 68 %, respectively. This superior protection is attributed to three primary mechanisms: physical barrier of LDH film with CaCO 3 particle, chloride absorption into LDH flakes, and release of inhibitor ions from LDH film. Typically, the Mg-Fe-pAB-LDH film have a Cl − adsorption capacity of 0.368 mol/m 2 and a pAB − release capacity of 0.217 mol/m 2 . Meanwhile, the corrosion protection performance decreases as the chloride concentration increases, indicating that the LDH film used for high-chloride environments need further optimization.