马氏体时效硬化不锈钢在NaCl和Na2SO4混合介质中的电化学腐蚀行为

Electrochemical Corrosion Behavior of Martensite Aging Hardened Stainless Steel in NaCl and Na2SO4 Mixed Solution

目前有关马氏体时效硬化不锈钢耐蚀性的研究还不充分,在Cl-和SO2环境中的腐蚀行为和耐蚀性均需充分探讨。通过极化曲线、电化学阻抗法(EIS)和肖特基(Mott-Schottky)曲线的测定,分析了马氏体时效硬化不锈钢在NaCl和Na2SO4混合介质中的电化学腐蚀行为。结果表明:随Cl-浓度的增大,点蚀电位负移,材料的耐点蚀性能下降;在混合溶液中,当Cl-和SO42-摩尔比为1∶3时,自腐蚀电流密度最小,试样的耐蚀性最强。马氏体时效硬化不锈钢的钝化膜在负于平带电位范围,表现为n型半导体;在高于平带电位时,表现为p型半导体,这与组成钝化膜的Cr和Fe氧化物半导体性质有关。当成膜电位为0.2 V时,平带电位负移,施主密度和受主密度均最小,钝化膜氧/金属离子空缺最少,侵蚀性Cl-在钝化膜表面的特性吸附较弱,有利于提高不锈钢的耐局部腐蚀性能。

The electrochemical behavior of martensite aging hardened stainless steel in NaCl and Na2SO4 mixed solution was analyzed by measuring the polarization curves,electrochemical impedance spectroscopy(EIS)and Mott-Schottky curves.Results showed that with the increase of Cl-concentration,the pitting potential decreased,and thereby pitting resistance decreased.In the mixed solution,when the molar ratio of Cl-and SO42-was 1∶3,the self-corrosion current density was the minimum,and the corrosion resistance of the sample was the strongest.The passive film of martensite aging hardened stainless steel performed n-type semiconductor in the negative potential range of flat band,and exhibited p-type semiconductor at high flat band potential,which was related to the properties of Cr and Fe oxide semiconductor that made up the passive film.Furthermore,when the membrane potential was 0.2 V,the flat band potential was negatively shifted,and the donor concentration and acceptor concentration attained the minimum,as well as the oxygen/metal ion vacancy in the passive film was the least.The adsorption of corrosive Cl-on the surface of the passive film became weaken,thereby improving the local corrosion resistance of stainless steel.