Q235碳钢缝隙腐蚀的电化学噪声研究

Investigation of Electrochemical Noise in the Crevice Corrosion of Q235 Carbon Cteel

应用电化学噪声和电化学阻抗技术研究Q235碳钢在NaHCO3+NaCl溶液中的缝隙腐蚀行为.结果显示,缝隙腐蚀过程可以被清楚地划分为3个阶段:孕育期、快速转换期和稳定发展期.电化学噪声的特征和噪声电阻在各阶段有着显著的变化.缝隙外、内表面积比(r)对缝隙腐蚀的孕育和发展有着十分重要的影响:r越大,孕育期越长.但是,在缝隙腐蚀稳定发展期,r较小时,缝隙外电极表面处于活性溶解状态,缝隙内外电位差很小,缝隙内腐蚀速率较小;倘如r很大时,则缝隙外电极表面处于钝态,缝隙内外电位差大,最终将导致严重的缝隙腐蚀.

The crevice corrosion behavior of Q235 carbon steels in a NaHCO3 ＋ NaCl solution was investigated by electrochemical noise （EN） and electrochemical impedance spectroscopy（EIS）. Three stages of crevice corrosion including the induction, the rapid transform and the stable development could be clearly distinguished. The characteristics of the electrochemical noise and the noise resistance Rn showed remarkable differences at each stage. The electrode area ratio （r） of outside to inside the crevice had a significant influence in the development of crevice corrosion. The time of the induction stage increased with increasing r. However, under the stable development stage of the crevice corrosion, the surface outside the crevice was at an active dissolution state when r was small, while the potential difference between outside and inside the crevice and the corrosion rate inside the crevice were small. When r was big, the surface outside the crevice was at a passive state and the potential difference between outside and inside the crevice was large, which causes serious crevice corrosion.