Experimental and Modeling Studies of Single Corrosion Pits on Pure Aluminum in pH 11 NaCl Solutions II. Pit Stability

Abstract

The critical solution composition required for sustained growth of hemispherical single corrosion pits on pure aluminum in basic sodium chloride solution was studied. Single corrosion pits were initiated by using a laser initiation technique. Electrochemical current interruption experiments were used to probe the effects of bulk solution concentration and potential on pit stability. A mathematical model was used to analyze the results from one type of current interruption experiment that investigated the effect of pit size on pit stability. The mathematical model extended the results of previous work (Part I, the previous article), which considered the profiles that develop during pit growth, to include transient behavior during the relaxation of the concentration profiles. The solution of the transient model was performed by first transforming the equations using the conformal mapping technique of Verbrugge et al. [Electrochim. Acta. 38, 1649 (1993)]. Numerical results were compared with experimental data and were interpreted on the basis of the hypothesis that a critical concentration of an ionic species is required in the pit for stability. © 2000 The Electrochemical Society. All rights reserved.