轧制纳米块体304不锈钢腐蚀行为的研究Ⅱ钝化膜保护性能

采用动电位极化曲线和Mott-Schottky分析等电化学测试手段,探讨了轧制纳米块体304不锈钢与普通304不锈钢在0.05mol/L H2SO4＋0.05mol/L Na2SO4溶液中钝化膜的保护性能;运用点缺陷（PDM）模型,分析了不同电位下在0.05mol/L H2SO4＋0.25mol/L Na2SO4溶液中两种材料形成钝化膜的半导体性质,阐述了导致两种钝化膜保护性能差异的根本原因.结果表明：两种材料表面钝化膜都具有n型半导体特征,氧空穴作为主要的载流子参与钝化膜的形成和溶解过程;钝化膜中载流子密度与钝化膜的形成电位之间满足幂指数关系,载流子在两种材料表面的钝化膜中的扩散系数非常接近,说明两种钝化膜遵从相似的形成和溶解机制,但轧制纳米块体304不锈钢中的载流子密度小于普通304不锈钢钝化膜中的载流子密度,从而使其钝化膜具有更好的保护性.

CORROSION BEHAVIOR OF NANOCRYSTALLIZED BULK 304 STAINLESS STEEL Ⅱ.PROTECTION OF THE PASSIVE FILM

By employing Mott-Schottky analysis in conjunction with the point defect model(PDM),we compared donor density and donor diffusion coefficients in the passive films formed on the surface of nanocrystallized bulk 304 stainless steel(NB304SS) and cast 304 stainless steel(304SS) in 0.05 mol/L H2SO4+0.25 mol/L Na2SO4 solution.The donor density at the metal/film interface of the NB304SS was lower than that at the metal film interface of the cast 304SS.Based on the Mott-Schottky analysis,an exponential relationship between donor density and formation potentials of the passive films on the NB304SS and the cast 304SS was built up.The results showed that the donor diffusion coefficients in the passive film formed on the surface of NB304SS was similar to that in the cast 304SS.The lower donor density restrained the electrochemical reaction in the passive film and improved the stability of the passive film.That is the reason why the passive film formed on the NB304SS was more protective.