The role of Na+ in Al surface corrosion studied by single-shot laser-induced breakdown spectroscopy

Abstract

Almost all previous studies on atmospheric corrosion of metals focused on anions such as Cl− and CO32−, ignoring the effects of cations such as Na+ in the atmosphere. Recent studies have shown that Na+ corrosion products such as NaAlCO3(OH)2 play an important role in the corrosion process of metals. However, detecting Na or its corrosion products remains a challenging task. In this work, Na depth profiling in Al corrosion samples was studied using single-shot laser-induced breakdown spectroscopy and 3D topography measurements. We found that the concentration of Na+ satisfies a power law, and it originates from atmospheric corrosion. An electrochemical corrosion model was established to interpret the invasion of Na+ into the Al matrix, and we employed COMSOL to simulate the corrosion process, by considering the controlling role of NaAlCO3(OH)2 on the atmospheric corrosion rate. Simulation results are consistent with the experimental data in different atmospheric environments.