长输管线在设计之初，常采用固定支墩对管线的穿跨越处或沿线进行锚固。随着我国长输管线的不断发展，输送距离的不断增加，管线上固定支墩处的腐蚀问题随之出现。固定支墩处一般采用外套管进行保护，然而对施加了阴极保护的管线来说，套管处容易产生电流屏蔽效应，增加了管线的腐蚀风险。分析油田现场腐蚀案例后发现腐蚀情况往往发生在套管边缘处。通过对各类防腐技术进行综合比较，分析套管对阴极保护电流产生屏蔽及管线发生腐蚀的原因，并采取一系列腐蚀防护措施来延长其使用寿命。整改措施分两种，一种是在环形空间充填电解质或绝缘材质，并做好套管处的密封工作，另一种是在套管处增加牺牲阳极保护，并严格把控现场施工材料中的氯离子含量，目前这两种方式对减缓套管内管线的腐蚀具有一定的作用。

At present, with the development of long-distance transportation pipelines in China and the increasing of transportation distance, there are often fixed piers at the crossing point or along the route in the design process of external transportation pipelines.These weak areas are often protected by external casing, whereas for cathodic protection, these areas are more likely to have a shielding effect on the cathodic protection current and increase the corrosion risk of the pipeline.By analyzing the corrosion cases in the field, it is found that the corrosion usually occurs at the edge of casing.This paper makes a comprehensive comparison of various anticorrosion technologies, and finds out the reason for casing shield to cathodic protection current or the pipeline corrosion, and adopts a series of corrosion protection measures to prolong its life.Based on the investigation of the development status of protection at home and abroad, the rectification measures can be divided into two types: one is to fill the annular space with electrolyte, and the other is to inject the insulating material with good air tightness into the casing.