Effect of sulfate on the pitting potential of austenitic stainless steels 18Cr8Ni and 17Cr6Mn5Ni in chloride media

Abstract Pitting corrosion resistance of two austenitic stainless steels, 18Cr8Ni (Type 304L or UNS S30403 stainless steel) and 17Cr6Mn5Ni, was evaluated in three electrolytic solutions containing a fixed concentration of 0.6M sodium chloride and different additions of sodium sulfate, 0.06M, 0.15M or 0.6M. Cyclic potentiodynamic polarization tests were performed on as-received samples and on specimens annealed at 1010°C, 1040°C, 1070°C or 1100°C. The best pitting corrosion resistance was presented by the 17Cr6Mn5Ni steel annealed at 1070°C or 1100°C, with lower delta ferrite contents, in the electrolyte with the highest sulfate concentration. It can be found that the addition of sodium sulfate inhibits pitting corrosion and has a better inhibitor effect in the high manganese steel.

摘要：本研究评估了18Cr8Ni（304L型或UNS S30403不锈钢）与17Cr6Mn5Ni两种奥氏体不锈钢的点蚀抗力，测试在三种固定含有0.6M氯化钠、添加不同浓度（0.06M、0.15M或0.6M）硫酸钠的电解液中开展。研究对供货态试样以及经1010℃、1040℃、1070℃或1100℃退火的试样进行了循环动电位极化测试。在硫酸钠浓度最高的电解液中，经1070℃或1100℃退火、δ铁素体含量更低的17Cr6Mn5Ni钢表现出最优的点蚀抗力。结果表明，硫酸钠的添加可抑制点蚀，且在该高锰钢中展现出更优的缓蚀效果。