The Effect of CO[sub 2] on the NaCl-Induced Atmospheric Corrosion of Aluminum

A laboratory study of the effect of and NaCl on the atmospheric corrosion of aluminum is reported. The samples were exposed to pure air with 95% relative humidity and the concentration of was <1 and 350 ppm, respectively. Sodium chloride was added before exposure (0, 14, and 70 μg/cm 2 ). The main result is that the NaCl-induced atmospheric corrosion of aluminum is about 10 to 20 times faster in -free humid air compared to air containing ambient levels of It is suggested that the rapid corrosion of aluminum coated with NaCl in humid -free air is connected to high-pH areas in the surface electrolyte that develop due to the cathodic reduction of oxygen. The anodic dissolution of aluminum is known to be enhanced by high pH. The unexpected corrosion-inhibitive effect of is explained by the neutralization of the surface electrolyte. In the absence of bayerite, forms. Only minute amounts of carbonate were found on the surface after exposure to -containing air. © 2001 The Electrochemical Society. All rights reserved.