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设计制备了新型高氮低镍奥氏体不锈钢(高氮钢)。采用阳极动电位极化法测量了此钢在不同浓度和不同pH值的NaCl溶液中的点蚀电位,获得了点蚀电位随溶液浓度及pH值变化的关系曲线,并与800H钢进行了对比。用扫描电镜(SEM)对样品表面进行了形貌观察对点腐蚀坑处进行了线扫描,分析了高氮钢耐点蚀的机理。研究表明在不同浓度和pH值的NaCl溶液中,高氮钢的点蚀电位达到1.2V(va SCE)以上,800H钢的点蚀电位在0.3 V(vs SCE)以下。扫描图显示腐蚀区域内高氮钢的点蚀坑稀少且面积较小,800H钢的点蚀坑密集且面积较大。线扫描表明氮在腐蚀坑内的含量略有下降;氮在钝化膜/金属界面富集,形成NH_4~+,并且抑制侵蚀性Cl~-的吸附是提高高氮钢耐蚀性的原因。
Design and preparation of a new type of high nitrogen and low nickel austenitic stainless steel (high nitrogen steel). The pitting potentials of this steel in NaCl solution with different concentrations and different pHs were measured by anodic potentiodynamic polarization. The relationship between pitting potential and solution concentration and pH value was obtained and compared with that of 800H steel . Scanning electron microscopy (SEM) was used to observe the surface morphology of the sample. The pitting corrosion was observed by a line scan and the mechanism of pitting corrosion resistance of high nitrogen steel was analyzed. The results show that the pitting corrosion potential of high nitrogen steel is above 1.2V (va SCE) and that of 800H steel is below 0.3 V (vs SCE) in NaCl solutions with different concentrations and pHs. Scanning images show that the corrosion zone of high nitrogen steel pits are sparse and small area, 800H steel pits dense and large area. The line scan shows that the content of nitrogen decreases slightly in the corrosion pits. Nitrogen enrichment at the passivation film / metal interface to form NH_4 ~ + and inhibit the adsorption of aggressive Cl ~ - is the reason for improving the corrosion resistance of high nitrogen steel.