埋地管线阴极保护屏蔽剥离涂层下薄液腐蚀环境特征及演化  

CHARACTERISTICSAND EVOLUTION OFTHIN LAYER ELECTROLYTE ON PIPELINE STEEL UNDER CATHODIC PROTECTION SHIELDING DISBONDED COATING

作　　者：闫茂成[1] 王俭秋[1] 韩恩厚[1] 孙成[1] 柯伟[1] 

机构地区：[1]中国科学院金属研究所国家金属腐蚀控制工程技术研究中心,沈阳110016

出　　处：《金属学报》2014年第9期1137-1145,共9页Acta Metallurgica Sinica

基　　金：国家自然科学基金重点项目51131001;教育部留学回国人员科研启动基金项目资助~~

摘　　要：构建了埋地管线表面剥离高绝缘性聚乙烯(PE)涂层下模拟缝隙实验装置,采用微电极技术研究阴极保护(CP)水平和环境气氛(CO2和O2)条件下剥离涂层下缝隙薄液电化学环境(电位和溶液pH值等)特征及其演化规律,探讨剥离涂层下近中性pH环境存在条件.结果表明,不同阴极保护水平和CO2分压条件下,剥离涂层下可出现近中性到高pH值各种薄液环境.高阴极保护电流使管表产生并维持高pH环境;大面积剥离、阴极保护屏蔽或缺失和CO2的缓冲作用可使剥离涂层下封存近中性pH应力腐蚀开裂(SCC)敏感薄液环境;由剥离涂层下缝隙薄液pH值可判断剥离涂层下阴极保护有效性及其屏蔽程度.External corrosion and stress corrosion cracking （SCC） have been observed in a thin layer electro- lyte under disbonded coating shielding cathodic protection （CP）. In this work, characteristic and evolution of the thin layer electrolyte environment （potential, pH, etc.） on pipeline steel under disbonded coatings were investigated by microelectrode technology in a simulating crevice cell at various CP levels and different atmosphere conditions （CO2 and O2）. The results show that pH of the thin layer electrolyte under the disbondment varies from near neutral to the value as high as 12, depending on the amount of CP current and CO2. CP current on pipeline surface initiates a high pH environment on the steel surface. Due to the CP shielding effect and a high CO2 content, a near-neutral pH environment may exist under disbonded coating. The CP effectiveness and the shielding effect of the disbond-ment can be estimated by measuring pH of the thin layer electrolyte under disbonded coatings.

关 键 词：管线钢 土壤腐蚀 3PE防腐层 阴极保护 薄液膜 应力腐蚀开裂(SCC) 

分 类 号：TG172.9[金属学及工艺—金属表面处理]