弃置海洋平台导管架牺牲阳极消耗过快的原因分析

Corrosion analysis of sacrificial anode used in abandoned jacket platform

对某油田弃置海洋平台导管架阴极保护系统进行了检测,发现导管架牺牲阳极块消耗过快。分析表明:牺牲阳极表面覆盖大量的腐蚀产物和海洋生物,导致牺牲阳极表面发生了局部腐蚀,牺牲阳极表面分布着深度不一的点蚀坑;扫描电镜观察牺牲阳极部分区域出现铝合金晶粒脱落,说明局部腐蚀是造成牺牲阳极块消耗过快的主要原因。对牺牲阳极块的电化学测试结果表明:腐蚀产物对开路电位有影响,牺牲阳极工作15 a后的开路电位已不满足国家标准的要求。

The sacrificial anode of abandoned jacket platform in an oil field was detected, and it was found that the sacrificial anode block of jacket platform corrodes fast. The study showed that the sacrificial anode surface was covered with a large number of corrosion products and marine organism, resulting in local corrosion. Corrosion pits with different depths were distributed over the surface, and the pit depth near support foot could reach about 5 cm;scanning electron microscope found that aluminum alloy grains fell off in some areas of sacrificial anode, indicating that local corrosion is the main reason for rapid consumption of sacrificial anode block. Electrochemical test of the sacrificial anode block showed that the corrosion products have an impact on open circuit potential, and open circuit potential for sacrificial anode after 15 years of operation can not meet the requirements of national standard.