Methanolic corrosion behaviour of 5052 Al–Mg alloys sheets under dry and moist conditions

Abstract

This study presents a comprehensive investigation of the corrosion behaviour of Aluminium 5052 in methanol under dry conditions and examines the influence of water content on this process. A marked difference in corrosion characteristics was observed between the two environments. The transition in mechanism from dry alcoholate-induced pitting corrosion to wet uniform corrosion was established through detailed analysis of corrosion products using advanced microscopic (including electron microscopy) and spectroscopic techniques. Under dry conditions, corrosion proceeds via methoxide formation followed by its decomposition to Al₂O₃, leading to localised pitting. Cracks could be observed at the bottom of these pits. In contrast, the addition of water to methanol promotes the formation of a uniform and stable Al(OH)₃ film, significantly altering the corrosion mode. Notably, introducing as little as 0.5 vol% water into methanol, while exerting negligible impact on combustion properties, substantially mitigates pit and crack formation associated with corrosion.