Friction stir processing coupled with LDH modification enables enhanced cathodic inhibition on Mg alloys

The formation of porous surface films during corrosion and the poor interfacial adhesion between the passive layer and the alloy substrate are two critical issues limiting the corrosion resistance of Mg alloys. In this work, we proposed a protection strategy combining friction stir processing (FSP) and layered double hydroxide (LDH) treatment for NS70 Mg alloy plates: the alloy plates were first subjected to FSP for microstructural refinement and homogenization, followed by the growth of LDH films doped with various cationic species. The dynamic recrystallization induced by FSP enhanced the intrinsic impedance of the substrate. The FSP coupled with Zn-Al LDH exhibited superior corrosion resistance, characterized by a noble shift in corrosion potential to −1.37 V vs. SCE and a reduction in corrosion current density to 6.33 × 10⁻⁷ A/cm². The surface hydrogen evolution rate decreased by 92% compared to that of the base metal after 144 h of immersion. The Zn-Al system revealed the superior interfacial separation energy among all LDH systems by first-principles theory calculations. The excellent separation energy of the Zn-Al system enabled it to resist delamination induced by corrosion product expansion, thereby contributing to the enhanced corrosion resistance of Mg alloys.