管道穿越段防腐层质量和阴极保护效果评估

Evaluation on quality of anticorrosive coating and effect of cathodic protection for crossing pipeline

在定向钻穿越段管道回拖过程中会出现防腐层损伤,而穿越段阴极保护电位分布规律与直埋段不同且难以测试,可能存在阴极保护不足,给穿越段管道带来腐蚀风险。对穿越段管道进行防腐层质量和阴极保护效果评估,采用临时阳极地床对两段穿越段管道进行馈电试验,使用电流环进行管中电流测试,结合地表电位、土壤电阻率、阴极极化行为等测试,计算穿越段管道防腐层电导率,评价防腐层质量;估算破损点阴极保护电位,形成穿越段管道防腐层质量和阴极保护有效性评价方法。评估结果表明:两段穿越管段的防腐层评估质量均为优秀,估算了较差一段管段破损点处的阴极保护水平,最正电位为-0.845 VCSE,建议适当提高阴极保护电流或采用100 mV的极化准则。该方法可用于评估在役穿越段管道的防腐层质量,为阴极保护的运维提供建议。(图4,表6,参24)

The coating may be damaged during the back dragging of horizontal directional drilling crossing pipeline,and inadequate cathodic protection may exist because the distribution law of cathodic protection potential of the crossing pipeline section is different from that of the straight section and it is difficult to test.All these conditions bring the risk of corrosion to the crossing pipeline.Hence,evaluation was carried out to the quality of the anticorrosive coating and the effect of cathodic protection for the in-service crossing pipeline.During the evaluation,feeding test was conducted with temporary anode groundbed,in-line current test was carried out with current loop,and tests based on surface potential,soil resistivity and cathodic polarization behavior were conducted for the crossing section.On this basis,the conductivity of the anticorrosive coating of the crossing pipeline was calculated,and the quality of the anticorrosive coating was evaluated.Additionally,by estimating the cathodic protection potential of the damaged point,a method was formed for the evaluation of the quality of the anticorrosive coating and the effect of cathodic protection of the crossing pipeline.For the two crossing pipeline sections in the case study,the quality of the anticorrosive coating was evaluated as excellent for both,and for the section with lower quality,the cathodic protection at the damaged point was estimated,with the most positive potential of-0.845 VCSE.Therefore,it can be recommended to appropriately increase the cathodic protection current or to adopt the 100 mV polarization criterion.As indicated by the test results,the method is applicable to the evaluation of the anticorrosive coating quality of the in-service crossing pipeline and it also provides suggestions to the operation and maintenance of cathodic protection.(4 Figures,6 Tables,24 References)