埋地管线剥离覆盖层下阴极保护的有效性

EFFECTIVENESS OF CATHODIC PROTECTION UNDER SIMULATED DISBONDED COATING ON PIPELINES

由微小缝隙模拟管线剥离覆盖层(涂层)下的局部电化学环境,用微电极技术测量了缝隙内局部电位及pH的分布,研究了缝口阴极保护电位、剥离区几何形状、溶液电导率等因素对剥离区内部局部环境及阴极保护水平的影响。结果表明,剥离区内电位降(电位梯度)主要集中在破损口附近,而剥离区深处接近自然腐蚀状态;剥离区内有效保护距离随缝口保护电位负移而增加,但缝口过保护并不能有效提高剥离区保护效果。阴极保护可使剥离区局部电化学环境pH升高、电导率增大。

The local using microelectrodes. potential and pH along a crevice simulating disbonded coating on pipelines were measured The effectiveness of cathodic protection （CP） in the local environment and the effects of applied cathodic potential, geometry of the crevice and solution conductivity were investigated. The results showed that the IR drop in the disbondment mainly occurred in the vicinity of the opening. The distance effectively protected by CP increased with the decreasing applied potential. However, hydrogen evolution had a reverse effect when an overprotection potential was applied. The additional effect of CP was shown to be the modification of the local environment, such as increase of pH and conductivity of solution, which was beneficial to corrosion controlling as well as direct polarization of the exposed steel at the holiday.