铬对碳钢在NaHCO_3/NaCO_3缓冲溶液中所成钝化膜半导体性能的影响

应用电化学阻抗谱技术研究铬对碳钢钝化膜半导体性能的影响.实验表明,在碳酸氢钠/碳酸钠缓冲溶液中碳钢形成的钝化膜具n型半导体特性,而含有3%铬的碳钢钝化膜则呈n-p型半导体特性,随着成膜电位的增加,以上两种钝化膜之Mott-Schottky直线部分的斜率均呈增大的趋势,表明成膜电位升高,膜内的杂质密度减小,但铬的加入使得碳钢钝化膜的施主密度增加约一个数量级,从而增加了碳钢点蚀发生的趋势.EIS分析表明:铬的加入降低了钝化膜的传递电阻R1和膜电阻R2,特别是膜电阻R2下降达3个数量级,这就有可能增加碳钢在高pH值环境中的腐蚀.

Influence of Chromium on the Semi-Conductive Property of Passive Film Formed on Carbon Steel in Bicarbonate/Carbonate Buffer Solution

The influence of chromium on the semi-conductive property of the passive film formed at carbon steel in bicarbonate/carbonate buffer solution,is investigated by using electrochemical impedance spectroscopy(EIS).The results showed that the passive film fomed at carbon steel appeared an n-type semi-conductive property,but if the passive film formed at carbon steel with 3% chromium content exhibited an a-p semi-conductive charatcer.The slopes of Mott-Schottky plot of two passive films increased with rising the formation potential,it indicating the defect density of the film decreasing,but for the passive film formed at carbon steel with chromium additive,its donor density was lower about one order of magnitude than that of passive film formed at carbon steel,this showed that the addition of chromium can increase the occurrence of the pitting corrosion.EIS experimental results raveled chromium increased the values of transfer impedance R1 and film impedance R2.Especially,the film impedance R2 was lower about three order magnitudes than that of carbon steel,it illustrated that the addition of chromium may increase the corrosion occurrence in the environment with high pH value.