Insight into corrosion and corrosion fatigue behavior of Mg alloy via preferential adsorption of inhibitor

The combined effect of cyclic loading and corrosive environment accelerates corrosion fatigue and therefore shortens service life of Mg alloy when used in automotive and aerospace applications. Enhancement the corrosion and corrosion fatigue performance are of the utmost importance to ensure the service reliability of Mg alloys. In the present study, the influence of inhibitor (barbituric acid) on corrosion and corrosion fatigue performance of Mg-Al-Ca alloy has been thoroughly investigated for the first time. It was found that inhibitor is preferentially adsorbed on basal plane compared to non-basal planes of Mg substrate, leading to a high inhibition efficiency of 90% after 7 days immersion in NaCl solution. Molecular dynamics simulations and density functional theory calculations further corroborated that the basal plane exhibits lowest adsorption energy and most pronounced charge density, suggesting that adsorption of inhibitor is crystal-plane-dependent on the Mg surface. The results demonstrated that the corrosion fatigue strength at a defined life (1 × 10 6 cycles) of Mg alloy in a pre-damaged condition has been increased by 100% in the presence of inhibitor. The superior performance originates from suppression of pitting corrosion on various crystal planes, which consequently delays the initiation of corrosion fatigue cracks.