残余应力存在时Cl^-对304不锈钢管道点蚀行为的影响

This paper explores the effects of residual stresses on the pitting corrosion of 304 stainless steel pipes. The open circuit potential(OCP), polarization test, electrochemical impedance spectroscopy(EIS), Mott-Schottky and other methods are used to study the effects of stresses and Cl^- concentration on the corrosion of cold-bent 304 stainless steel elbows. The pitting corrosion and passive film characteristics of different parts of the elbow in 100 and 1 000 mg/L Cl^- solution were tested. How the stresses and Cl^-concentration affect the pitting corrosion of stainless steel and the corresponding corrosion mechanism were analyzed. The results show that the residual stresses on the U-bend tensile surface and compression surface of 304 stainless steel after cold machining are tensile and compressive stresses respectively, and that there is almost no stress on the undeformed straight pipe. The corrosion test shows that when the Cl^- concentration is 100 mg/L, the residual stress will enhance the ability of stainless steel to resist Cl^- pitting corrosion and reduce the carrier concentration of the passivation film. The effects of tensile stress are stronger than those of compressive stress and the maximum pit depth is 80.426 μm). When the Cl^- concentration is 1 000 mg/L, both tensile and compressive stresses reduce the ability of stainless steel to resist Cl^- pitting corrosion, and the pit size at the tensile stress is the greatest under the same concentration condition(117.956 μm).