The NaCl-induced atmospheric corrosion of aluminum -: The influence of carbon dioxide and temperature

Samples were exposed to purified air with 95% RH and <1 or 350 ppm CO2 in the presence (70 or 14 μg/cm(2)) or in the absence of NaCl. Temperature was 4, 10, 22, 38, 50, and 60°C. Samples were analyzed by gravimetry, X-ray diffraction, ion chromatography and environmental scanning electron microscopy/energy dispersive X-ray analysis. The two main results are the strong, nonlinear temperature dependence of corrosion and the inhibitive effect of CO2 at ambient temperature. NaCl-treated aluminum corrodes rapidly in humid CO2-free air because high pH areas develop due to the cathodic reduction of oxygen. This results in an enhanced anodic dissolution of aluminum. The inhibitive effect of CO2 is attributed to its acidity. CO2 neutralizes the hydroxide formed with the result that the corrosion rate decreases. (C) 2003 The Electrochemical Society.