Effect of SO 2 and pH on the Anodic Behavior and Pitting Corrosion of Alloy 600
Résumé
The anodic behavior and pitting corrosion of Alloy 600 in solutions containing low concentrations of and were studied by cyclic voltammetry near the activation peak. The results are presented in the form of an vs. corrosion diagram for different sweep rates. A model based on the competitive adsorption of and is proposed. The effect of pH on the various adsorption states is discussed. The adsorption of anions gives rise to the breakdown of the oxide film and that of provides a protective effect; the adsorption of depends very strongly on the pH. Two types of pitting were observed at different potentials in the activation range. Relatively few and deep pits occur at low concentrations (−0.47 V/SSE) while numerous and shallow pits develop at higher concentrations (−0.52 V/SSE).