Evaluation of pitting susceptibility of aluminum anodized in borate and phosphate solutions using EN analysis

Abstract

The electrochemical noises (ENS) obtained from anodized aluminum in 0.1 M NaCl solution have been analyzed to evaluate the resistance to pitting corrosion as a function of anodizing solution and formation potential. The application of stochastic theory to the electrochemical noises provides more additional information on corrosion process than that of shot-noise theory alone. The occurrence of two linear regions on one Weibull probability plot indicated that the present analysis method allowed us to distinguish between pitting corrosion and uniform corrosion in an engineering sense. Moreover, from the lower pit embryo formation rate of aluminum anodized in boric-ammonium phosphate solution compared to the rate of aluminum anodized in boric-borate solution, it was concluded that the oxide film formed in boric-ammonium phosphate solution provides good pitting corrosion resistance, as compared with the film formed in boric-borate solution. (C) 2007 The Electrochemical Society.