长输管道在穿越河流、公路位置通常会采用箱涵的建设方式,与箱涵外的主管道相比,箱涵内管道电位难以测试;箱涵的钢筋结构可能会吸收阴极保护电流使箱涵内管道阴极保护电位不足,给穿越段管道带来腐蚀风险。为研究箱涵内管道的电位分布规律和腐蚀特点,在实验室搭建管道穿越箱涵的试验装置,测试和对比管道和箱涵在短路和未短路2种工况条件下,进箱涵、箱涵内和箱涵外管道的阴极保护电位和腐蚀速率;利用仿真软件进行箱涵屏蔽计算,探讨了箱涵对管道的阴极保护屏蔽效应。结果表明:箱涵与管道未短路时,箱涵内管道的阴极保护达标,腐蚀风险低;箱涵与管道短路时,箱涵内管道因箱涵的电流屏蔽效应,阴极保护电位不达标,腐蚀风险高,提高阴极保护输出电流,可以缓解箱涵内管道的腐蚀风险。
Box culverts are usually used in the construction of long-distance pipelines crossing rivers and highways. Compared with the main pipe outside the box culvert, it is difficult to measure the potential of the pipe inside the box culvert. The steel reinforcement structure of the box culvert may absorb the cathodic protection current so that the cathodic protection potential of the pipe in the box culvert is insufficient, which will bring the risk of corrosion to the pipeline in the crossing section. To investigate the potential distribution law and corrosion characteristics of the pipeline in the box culvert, the experimental device for pipeline crossing box culverts was built in the laboratory to test and compare the cathodic protection potential and corrosion rate of pipelines entering, inside, and outside the box culverts under two working conditions of short circuit and non-short circuit between pipelines and the box culverts. The shielding calculation of box culverts was conducted using simulation software, and the cathodic protection shielding effect of box culverts on pipelines was ultimately explored. Results showed that cathodic protection inside the box culverts met established criteria and corrosion risk was minimal in the absence of a short circuit between the box culvert and pipelines. Conversely, when a short circuit between the box culvert and pipelines occurred, the cathodic protection potential of pipelines inside the box culverts fell below the criterion due to the current shielding effect of the box culvert, thereby increasing the corrosion risk. Under such circumstances, an increase in the output current of the rectifier is necessary to mitigate the risk of corrosion of pipelines inside the box culverts.
