应用X射线光电子能谱(XPS)和表面增强拉曼光谱(SERS)考察18-8不锈钢表面电化学改性钝化膜各层次的化学组成.XPS的结果表明电化学改性处理可使钝化膜老化.膜层中含大量的CrO3,但未检测到CrO42-.在膜的各个层次均发生铬的富集,而在最外层铬的含量并非最大.表明在改性处理过程中,铬优先溶解,部分物种可进入溶液.铁在膜的外层存在Fe(Ⅱ)和Fe(Ⅲ)两种氧化态,同样有利于非晶态结构的形成.原位SERS测试的结果指明CrO42-主要存在于膜的最表层,进一步探明不锈钢表面电化学改性钝化膜的离子选择特性.
In order to make further insight into the mature of passivity,the combination of XPS and SERS was employed to ex-situ and in-situ characterize the chemical composition and structure of electrochemically modified passive film of 18/8 stainless steel.It was evidenced that the electrochemical modification gave rise to dehydration of the passive film.There existed an abundance of CrO3 in the outer layer of passive film ,but no CuO42- was sensed by XPS measurements.The enrichment of Cr apeared throughout the passive film, and the maximum of it did mot locate at the outmost layer.It implied that the preferential solvating hapned during the electrochemical modification.Like the coexistence of Cr2O3 and CrO3 in the barrier layer, the oxides of Fe(Ⅱ) and Fe(Ⅲ) species at the outer ayer played a beneficial role in the formation of non-crystalline passive film.It was revealed that from in-situ SERS and ion selective screen of CrO42- may be formed on the surface, which repulsed the attack of the aggressive ions and strengthened the stability of the electrochemically modified passive film of 18/8 stainless steel.
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