埋地管道防腐保温层下的电化学腐蚀行为

Electrochemical Corrosion Behavior of Buried Pipeline under Anticorrosion and Thermal Insulation Layer

运用电化学技术,通过电极电位、耦合电流、交流阻抗图谱(EIS)测试分析,研究埋地保温管道破损点及远离破损点处的电化学腐蚀行为。结果表明:氧浓差导致破损点及远离破损点试样的电极电位出现明显差异,即破损点处电极电位较正,作为阴极,具有阴极保护效应,腐蚀速率仅为0.1593 mm/a;远离破损点位置电极电位较负,作为阳极,具有接触腐蚀效应,腐蚀速率均高于破损点位置,最高为0.5316 mm/a;受到模拟介质有效距离效应的影响,距离破损点最近位置试样的阳极电流密度最大,腐蚀最为严重;随着温度升高,阴极区与阳极区的电位差和耦合电流密度增大,远离破损点的阳极区腐蚀加剧。自腐蚀电位下T/S-52K管线钢的腐蚀具有阴极浓差极化控制为主的电极反应特征;防腐保温层破损后,破损点处具有明显O2扩散控制的阴极反应特征,而远离破损点位置具有明显活化极化控制的阳极反应特征;距破损点距离越近,电荷转移电阻越低(其中2#试样R_(t)仅为430.2Ω·cm^(2)),金属离子化趋势越强。

The electrochemical corrosion behavior of buried thermal insulation pipeline at the damaged point and the point far away from the damaged point was studied by the test and analysis of electrode potential,coupling current and EIS.The results show that:the oxygen concentration difference leads to obvious difference in electrode potential at the damaged point and the point far away from the damaged point,that is to say,the electrode potential at the damaged point is relatively positive,the damaged point is protected as cathode,and its corrosion rate is only 0.1593 mm/a;The electrode potential far away from the damaged point is more negative.As anode,the location has contact corrosion effect,and its corrosion rate is higher than that at the damaged point,with the highest corrosion rate value of 0.5316 mm/a;Affected by the effective distance of the simulated medium,the anode current density of the sample closest to the damaged point is the largest,and the corrosion of the sample is the most serious;with the increase of temperature,the potential difference and coupling current density between the cathode area and the anode area increase,and the corrosion in the anode area far away from the damaged point intensifies.The corrosion of T/S-52K pipeline steel under the self corrosion potential has the electrode reaction characteristics dominated by the cathodic concentration polarization control;After the anticorrosive insulation layer is damaged,the cathode reaction at the damaged point is controlled by O2 diffusion,while the anode reaction far away from the damaged point is controlled by activation polarization;The closer the distance to the damaged point is,the lower the charge transfer resistance is(in which the R_(t) of 2#sample is only 430.2Ω·cm^(2)),and the stronger the ionization trend of metal is.