THE SIGNIFICANCE OF CHLORIDES ON THE PITTING CORROSION OF CARBON STEEL IN HOT POTASSIUM CARBONATE SOLUTIONS

摘要

This investigation was carried out to determine the effect of chloride ions on the pitting corrosion of carbon steel in potassium carbonate solutions with pH values and solution ionic strengths reflecting hot potassium carbonate (HPC) acid gas processing plant conditions. The pitting potential was evaluated from polarisation curves. For solutions with pH values of 8.5 to 9.5 the pitting potential was much more positive than the free corrosion potential and therefore pitting corrosion is not an issue. However, the carbon steel was susceptible to pitting corrosion in the pH 8.0 solution with high anodic inhibitor concentrations and chloride concentrations in excess of 0.5wt %. As these chloride concentrations are considerably above the maximum concentration of 0.1 wt% recorded in plant, chloride is judged not of concern.