Effect of passive film quality on corrosion resistance of 304 austenitic stainless steel after air exposure and chemical passivation was investigated by using electrochemical impedance spectra.A novel inspection of the film quality was proposed based on cathodic reduction and chromaticity inspection.The results show that the compactness of passive film and corrosion resistance for the sample after chemical passivation are superior to that after air exposure.The chromaticity measurement is dependent on the applied potential for the samples after air exposure.The chromaticity measured value increases with decreasing potentials when the applied potential is lower than the reduction potential of outer Fe-rich oxide in passive film.However,the chromaticity for the samples after chemical passivation is close to 0.Based on cyclic voltammetry,it reveals that the chemical passivation improves the corrosion resistance of 304 stainless steel by enhancing the compactness of inner Cr-rich oxide in passive film.Experimental results suggest that the chromaticity inspection could be utilized to numerically characterize the quality of passive film.%采用电化学阻抗比较空气暴露和化学钝化304奥氏体不锈钢表面钝化膜质量对其耐蚀性的影响,并提出一种结合阴极还原和显色测量的钝化膜质量检测新方法.结果表明:化学钝化304不锈钢表面钝化膜的致密性和耐蚀性均高于空气暴露样品;空气暴露样品表面钝化膜的显色检测值与还原电位相关,当电位低于钝化膜外层富铁氧化物的还原电位时,显色值随还原电位的降低而增大;化学钝化样品的显色检测值均接近于0;结合循环伏安分析可知,化学钝化通过提高钝化膜内层富铬氧化物的致密性来改善不锈钢耐蚀性,基于阴极还原的显色检测可实现钝化膜质量的数值化表征.
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