Corrosion behaviour of Alloy 800 in high temperature aqueous solutions: Electrochemical studies

Abstract The anodic behaviour and passivity breakdown of Allot 800 in aqueous solutions of sodium chloride, sodium sulphate and sodium bicarbonate were studied by electrochemical techniques in the temperature range from 60°C to 280°C. The pitting resistance and pitting morphology of the alloy in chloride plus sulphate and chloride plus bicarbonate mixtures, at 60°C and 280°C, were also examined. Increasing bicarbonate or sulphate additions to chloride solutions shift the characteristic pitting potential of Alloy 800 to higher values, both at low and high temperatures. Changes in pitting morphology were observed in sulphate containing solutions while the morphology of the attack found in bicarbonate containing solutions was similar to that in pure chloride solutions. Finally, no localized or substantial generalized corrosion was detected in pure sulphate or bicarbonate solutions at any temperature.