关键词: 铬, 碳钢, 半导体特性

Abstract: 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.

Key words: chromium, carbon steel, semi-conductive property, defect density