热带海洋大气环境下X70管线钢的缝隙腐蚀行为研究

目的研究X70管线钢在热带海洋大气实海环境下的缝隙腐蚀行为。方法在距离湛江东海岛海岸50m和200 m处分别搭建楔型缝隙模型,安装大气环境Cl-收集装置和自动气象监测站。结果距离海岸越近,风速越大,大气中Cl-沉降速率也越大,X70管线钢缝隙腐蚀越严重。X70管线钢在距离海岸50 m处发生缝隙腐蚀的最大缝宽约为0.96 mm,200 m处最大缝宽约为3.75 mm,50 m处缝隙腐蚀更严重。结论缝隙腐蚀区域形成了氧浓差电池,同时随着缝隙液中Cl-向缝隙内迁移,发生闭塞区电池自催化过程,在二者共同作用下,缝隙腐蚀区域较非缝隙腐蚀区域腐蚀更严重。

Crevice Corrosion Behaviors of X70 Pipeline Steel in Tropic Marine Atmosphere

Objective To investigate crevice corrosion behaviors of X70 pipeline steel in tropic marine atmosphere. Methods A wedge-type crevice model, Cl- -collecting device and automatic meteorological station were set up respectively 50 m and 200 m away from Donghai island of Zhanjiang. Results As close to the coast, the wind speed and the sedimentation rate of atmospheric Cl- got greater and the crevice corrosion of X70 pipeline steel was more serious. The maximal crevice width of X70 pipeline steel 50 meters and 200 meters away from the coast were respectively about 0.96 mm and 3.75 mm; the corrosion of X70 pipeline steel 50 m away from the coast was more serious. Conclusion Oxygen concentration cell forms in the area with crevice corrosion. The autocatalysis of cell generates in the occluded area as the migration of the Cl- in the liquid of the crevice gap. In the combination of the two mechanisms, the areas with crevice corrosion are more serious than other areas.