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

This study investigated the corrosion of aluminum in various ethanol/water mixtures. It has been shown that a critical corrosion temperature exists at which a sudden exothermic corrosion occurs. This critical corrosion temperature is dependent on 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 corrosion temperature. This increase is due to a reaction of water and carbonyl to carbonyl-hydrate which reacts with the aluminum oxide surface forming a passivation layer. The critical corrosion temperature has been defined by the reaction of aluminum with ethanol. Thereby, the same energy is always released, independent of the water concentration. However, the presence of water influences the activation energy of this reaction. The observed corrosion of aluminum depends on the exposed surface area. Consequently, with increasing surface area, a higher statistical failure rate is observed. This is most likely due to defects in the passivation layer of aluminum.