摘要
Magnesium (Mg) alloys are promising lightweight materials for various applications thanks to their low density and high specific strength. However, their poor corrosion resistance remains a critical limitation. Surface modifications, such as anodization, provide good wear resistance but limited corrosion resistance due to their porous and cracked structure. On the other hand, layered double hydroxide (LDH) coatings offer ion-exchange capability [1] but insufficient physical protection due to their hydrophilic nature and needle-like structure. Therefore, to combine the advantages and compensate for the drawbacks of each coating, we developed a multifunctional corrosion-resistant composite coating via sequential anodization, LDH electrodeposition, vanadate anion exchange, and myristic acid (MA) hydrophobic modification. This composite coating design provides both structural compactness and active protection against corrosion reactions. Microstructure characterizations confirmed that the electrodeposited Zn-Al LDH effectively sealed the large pores of the anodized film on the AZ31 Mg alloy, forming a defect-free composite coating. Through corrosion and electrochemical tests in 3.5 wt% NaCl solution, the hydrophobic composite coating with ion-exchange capability and vanadates corrosion inhibition substantially improved the corrosion resistance of the AZ31 Mg alloy. Electrochemical impedance spectroscopy (EIS) analysis showed that the composite-coated sample exhibited an over 500-fold increase in polarization resistance ( R p ), while potentiodynamic polarization (PDP) curves revealed an over 300-fold reduction in the corrosion current density ( i corr ) compared to the bare AZ31 Mg alloy. The corrosion protection and inhibition mechanism of the composite coating will be discussed based on electrochemical measurements and microstructure characterizations. References: [1] W.-L. Hsiao, P.-W. Chu, Coatings, 14 (2024) 1047. Figure 1