Localized Corrosion of Tantalum in Chloride-Containing Methanol Solutions—Effect of Water Concentration

Abstract

Abstract Tantalum is one of the most corrosion-resistant engineering materials. It is commonly used in harsh environments in the chemical process industry. However, it is known that tantalum is susceptible to localized corrosion in methanol solutions. It has been found that the pitting and repassivation potentials of pure Ta are a strong function of water concentration. Increasing the water concentration results in increased pitting and repassivation potential. The pitting potential is a stronger function of water concentration than the repassivation potentials. One-dimensional pit growth studies have shown that the pit growth of Ta is ohmically controlled. Repassivation transient data clearly indicate that the time to repassivate increases with decreasing water concentration. This suggests that the critical conditions for pit growth are sustained for a longer time at lower concentrations of water, leading to a lower pitting potential at lower concentrations of water.