Corrosion-resistant Mg(OH)₂/Mg-Fe layered double hydroxide (LDH) composite films on magnesium alloy WE43

Background: A new synthesis approach was developed for Mg-Fe layered double hydroxide (LDH) film on oxidised magnesium (Mg) alloy WE43 surface by cathodic electrodeposition. Methods: The synthesised Mg(OH)₂ surface layer provides essential divalent cations and a foundation for the direct growth of an Mg-Fe LDH film through the electrodeposition process with trivalent cations containing solution. Findings: The cross-section analysis results disclosed that the Mg(OH)₂ layer altered the typical morphology of LDH film, leading to structured LDH nanoplates with a thickness of approximately 3.5 µm. The formation of structured LDH nanoplates resulted from the perpendicular arrangement of the ab-faces of the crystallites to the WE43 surface, as seen from Field Emission Scanning Electron Microscopy (FE-SEM) images. Electrochemical tests in Hank's Balanced Salt Solution (HBSS) report the E_corr value increased by 0.24 V and a decrease in i_corr by one order of magnitude of Mg(OH)₂/Mg-Fe LDH composite films against its substrate. Furthermore, the impedance modulus values of Mg(OH)₂/Mg-Fe LDH composite films can achieve a magnitude of three times greater than its substrate. These results indicate that the Mg-Fe LDH film can effectively capture the corrosion anions during corrosion through the anion-exchange process, making it a promising surface modification for Mg alloy.