500kV输电线路铁塔塔脚腐蚀原因及处理方案

Causes and Treatment Scheme of Tower Foot Corrosion of a 500kV Transmission Tower

对某500kV输电线路铁塔塔脚出现严重腐蚀的现场宏观检查，对上底座腐蚀产物取样进行XRD，SEM和EDS分析。结果表明，塔脚的腐蚀是发生在上底座和护板表面的局部腐蚀，主要是大气中SO2对塔脚造成的腐蚀。塔脚所处的位置S02浓度最高，而锌和A3钢在SOz存在的条件下，腐蚀速率都高于在纯空气中（不含SO2），生成的腐蚀产物结构多孔疏松，且铁塔经常处于潮湿条件下的服役环境能够满足腐蚀持续进行的电化学条件。这些因素共同作用，导致塔脚的腐蚀速率很高，在1～2a的时间内腐蚀减薄已达50％。根据对腐蚀原因的分析，制定了相应的怛补加固和防腐伸涂料体系方案。

The causes of severe corrosion of a 500 kV transmission tower foot were analyzed and a fix scheme was formulated. The results of macro inspection, SEM, EDS and XRD analyses of corrosion products sampled from above pedestal show that the corrosion of tower foot occurring on the pedestal and protective plate surface was localized corrosion. The mainly reason was SO2 in atmosphere. The position of tower foot had the highest concentration of SO2. Because of the existence of SO2, the corrosion rate was much higher than that of in the pure air. The structure of corrosion products was porous and service environment was in moist condition, which met the conditions of electrochemical corrosion continuous development. These factors worked together and led to a very high corrosion rate of tower foot, the corrosion thinning reached 50% within 1-2 a. Thus a welding repair and anticorrosive coating system of corresponding solution was formulated.