Stress Corrosion Cracking of Sensitized AISI 304 Stainless Steel in Oxygenated High Temperature Chloride Solutions Containing Cupric (Cu²⁺) and Lead (Ph²⁺) Ions^⋆

The constant extension rate tensile (CERT) technique was used to determine the effects of moderate concentrations of Cu²⁺ and Pb²⁺ on the intergranular stress corrosion cracking (IGSCC) susceptibility of sensitized AISI 304 stainless steel (SS) in oxygenated aqueous solutions containing Cl^– ions at 250 C. The open circuit potential for each straining electrode was monitored as a function of time. The results indicated that both Cu²⁺ and Pb²⁺ enhance IGSCC susceptibility in high temperature (250 C) oxygenated chloride solutions. It was found that the addition of the cations increased the electrochemical potential of the steel; however, during straining, the potential dropped to more active (negative) values with time. Cupric ion exerts its most severe effect at a concentration of approximately 80 mg/L (ppm) in solution containing 0.2 mg/L of [O₂] and 104.1 mg/L of chloride ion. On the other hand, Pb²⁺ exhibited its most severe influence at a concentration of 25 to 30 mg/L in solutions containing 0.2 to 0.5 mg/L of [O₂] and 17.71 mg/L of chloride. These findings imply that the control of Pb²⁺ and Cu²⁺ is important in any procedures that are developed to minimize IGSCC of sensitized AISI 304 SS in high temperature aqueous environments.