Corrosion resistance of brazed aluminum in ethanol/water mixtures at high temperatures

摘要

This study investigated the corrosion of aluminum in various ethanol/water mixtures. It has been shown that a critical corrosiontemperature exists at which a sudden exothermic corrosion occurs. This critical corrosion temperature is dependenton presence of water and increases with increasing water concentration. This corrosion is independent of the atmosphere.Furthermore, it was demonstrated that denaturants in ethanol with a carbonyl group will further increase the critical corrosiontemperature. This increase is due to a reaction of water and carbonyl to carbonyl-hydrate which reacts with the aluminumoxide surface forming a passivation layer. The critical corrosion temperature has been defined by the reaction of aluminumwith ethanol. Thereby, the same energy is always released, independent of the water concentration. However, the presenceof water influences the activation energy of this reaction. The observed corrosion of aluminum depends on the exposedsurface area. Consequently, with increasing surface area, a higher statistical failure rate is observed. This is most likely dueto defects in the passivation layer of aluminum.