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中文摘要：
采用电位-电容测试和Mott—Schottky分析技术研究了碳钢／醇酸涂层在5％NaCl溶液侵蚀下腐蚀失效过程中的极化及半导体行为．浸泡2h，电极形成了MIS（Metal-Insulator-Semiconductor）结构，涂层半导体为n型导电，半导体载流子密度为4．99×10^9cm^-3，腐蚀仅受水和离子在涂层中的扩散控制；浸泡1d和2d时，涂层在电场下发生偶极极化，偶极电场阻碍载流子的迁移，偶极弛豫效应使微分电容随外加电位绝对值增大而减小，并造成电位-电容行为的频率依赖性；浸泡7～17d涂层发生空间电荷极化，碳钢与涂层形成了金属／半导体接触，随着浸泡时间延长，涂层载流子密度逐渐增加，平带电位正移，功函数逐渐减小，对电子束缚能力减弱，随外加电位的增加，金属／醇酸涂层界面势垒升高，空间电荷层成为阻挡层，电极载流子输运受涂层孔隙电阻、空间电荷层、金属基底反应动力学三重控制．
英文摘要：
Polarization and semiconductor behavior of alkyd coating coated on a carbon steel electrode in 5% NaCl solution during its degradation was investigated by potential-capacitance measurement, Mott-Schottky analysis and electrochemical impedance spectroscopy in this paper. An MIS （Metal-Insulator-Semiconductor） structure was generated when the electrode immersed in the electrolyte for 2 h, and carrier density of the n type coating semiconductor was 4.99 × 10^9 cm^-3. The corrosion was controlled by diffusion of aggressive ions and water in the coating at this stage. Dipole polarization happened under voltage in the coating which was immersed for 1 and 2 d, and the electric field caused by the dipole polarization baffled charge carrier transfer. Because of dipole relaxation, the differential capacitance decreased with raising absolute value of voltage, and frequency dependence of potential-capacitance behavior also occurred; after immersion for 7 d, space-charge polarization dominated and the carbon steel/coating was transformed into a metal-semiconductor contact. With extending the immersion time, cartier concentration of coating increased, and fiat band potential moved positively, so the work function of it decreased gradually, which resulted in weakening the binding ability of coating to electrons. Potential barrier on the interface of metal and semiconductor was heightened with raising the voltage, and also a barrier layer initiated on the interface. Carrier transport on the electrode was controlled by pore resistance of the coating, space charge layer and kinetics of corrosion reaction of substrate.
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