Effect of degradable (CaP and ZnO) nanoparticals void-plugging MgFe-LDHs film on the pitting-responsive behaviors of AZ31 magnesium alloy

The influence of degradable (CaP and ZnO) nanoparticles embedded in MgFe-LDHs film on protective-barrier and pitting-responsive behaviors of magnesium alloy were investigated. Cyclic-polarization studies in SBF indicated that LDHs/ZnO exhibited lower pitting-resistance but higher re-passivation ability compared to LDHs/CaP. Unexpectedly, different self-repairing effects and corroded-morphologies were observed after immersion in SBF. For LDHs/CaP, the additional layer induced by CaP shielded the intact film from corrosive-attacking, yielding tunnel-shaped corroded-channels. For LDHs/ZnO, the secondary zinc-containing layer covered corroded-pits by dissolution/recrystallization, retarding Cl− vertical attack to form shallow pits. In brief, the secondary-protective layer interferes with Cl− selective attack, governing the pitting propagation.