Prediction of Pitting Corrosion Damage of 316L Stainless Steel in NaCl and NaClO3 Cooperative Environment

NaClO3 is a major by-product of the chlor-alkali industry. Establishing a corrosion damage prediction method for 316L stainless steel (316L SS) in NaClO3 and NaCl cooperative environments is crucial for maintaining the service safety of chlor-alkali equipment. Electrochemical tests were conducted to obtain the reaction kinetic parameters of 316L SS in NaClO3 and NaCl environments. Based on COMSOL Multiphysics 6.2.290 simulation, the pitting corrosion behavior of 316L SS in a saturated NaCl and NaClO3 solution at 90 °C and the effect of by-product NaClO3 concentration on corrosion damage evolution were investigated. The simulated pitting depth of 316L SS in a saturated NaCl environment at 90 °C for 30 days was 18.7 μm, and the average pitting depth of the immersion experiment was approximately 21.1 μm, indicating that the simulated pitting depth was in good agreement with the experimental results. Furthermore, the potential, maximum current density and active-state dissolution of the metal were analyzed in NaCl and NaClO3 solutions. After adding NaClO3, the maximum potential, maximum current density and concentration of Cr(OH)2+ decreased by more than 41.5%, 86.4% and 91.2%, respectively. Both the tendency for pitting initiation and the pitting propagation rate of 316L SS were significantly reduced. It is noted that NaClO3 inhibits pitting of 316L SS in saturated NaCl environments.