破损涂层下管线钢的交流电干扰腐蚀行为

AC Interference Corrosion of Pipeline Steel Beneath Delaminated Coating with Holiday

构建了带破损点的剥离涂层管道腐蚀模拟实验装置,采用微电极技术研究交流干扰X80管线钢破损/剥离涂层下局部腐蚀行为及规律。结果表明:交流电干扰使涂层破损管线钢电位负向偏移;随交流电密度增大,X80钢的阳极溶解速率增大,腐蚀形态由均匀腐蚀逐渐向局部腐蚀转变;破损点处管线钢发生严重腐蚀,剥离区腐蚀程度稍有减缓;但施加100 A/m^2交流电时,剥离区深处X80钢表面仍出现了较严重的点蚀坑。从交流干扰的整流效应、阳极反应不可逆性及交流电对钢/环境界面双电层结构影响等角度讨论了交流电干扰对涂层破损下管线钢腐蚀行为的影响。

AC interference corrosion of X80 pipeline steel beneath a delaminated coating with an artificial damage is investigated via a simulated crevice cell by means of microelectrode technique in artificial neutral soil solution NS4. The results show that the applied AC interference may induce the negative shift of the free corrosion potential of X80 steel. With the increase of AC current density, the anodic dissolution rate of X80 steel increases, while the corrosion pattern changes from uniform corrosion to local corrosion. The corrosion of pipeline steel just on the damaged spot is the most serious, however, the corrosion attack of the steel beneath the delaminated coating around the damaged spot is slightly alleviated.When the AC interference current density increases up to 100 A/m2, serious pitting corrosion appears on X80 steel surface, where locates even far from the damaged spot beneath the delaminated coating. The influence of AC interference on the corrosion behavior of pipeline steel beneath the damaged coating was discussed from aspects of the rectification effect of the AC interference, the irreversibility of anode reaction and the effect of AC on the double layer structure at the interface steel/solution.