In Situ Fabrication of Nanostructured Layered Hydroxide Salt Coating and Its Enhanced Corrosion Resistance on Mg–Zn Alloy

In this study, a Mg–Zn layered hydroxide salt (LHS) coating was fabricated in situ on a Mg–Zn alloy (ZK61M) to enhance its corrosion resistance properties. The LHS coating was synthesized via a chemical process utilizing a carbonate solution, the pH of which was adjusted by using a sodium hydroxide solution. The surface morphology, composition, and structure of the LHS coating were examined. The findings confirmed the successful development of a uniform and dense LHS coating on the Mg–Zn alloy surface. The coating exhibits a distinct two-dimensional nanosheet-like layered structure. This was accomplished by adjusting the pH of the carbonate solution to 10 with a sodium hydroxide solution and maintaining the reaction at 50 °C for 4 h. The corrosion resistance of the LHS-coated Mg–Zn alloy was assessed through electrochemical impedance spectroscopy (EIS) and polarization curves in 3.5 wt % NaCl solution. The corrosion resistance assessments showed that the LHS-coated alloy displayed markedly improved resistance compared to that of the uncoated one. For instance, the corrosion potential (Ecorr) was measured at −1.3362 V, which is more positive than that of the uncoated Mg–Zn alloy at −1.4645 V. Additionally, the corrosion current density (Icorr) was reduced to 3.30 × 10–6A/cm–2, approximately 0.94% of that of uncoated Mg–Zn alloy, which was 3.51 × 10–4A/cm–2. The LHS coating effectively mitigated the corrosion process, serving as a protective barrier that hindered the ingress of corrosive agents into the substrate. This study offers significant contributions to the advancement of corrosion-resistant coatings for Mg–Zn alloys through in situ fabrication methods.