H_2S浓度和pH值对X65海管钢焊接接头腐蚀行为的影响

采用高压釜模拟海底集输环境,通过电化学测试技术、浸泡实验、SEM和XRD技术研究了H2S浓度和pH值对X65钢焊接接头腐蚀行为的影响。结果表明,X65钢焊接接头中热影响区的开路电位最负,焊缝最正,母材介于两者之间,腐蚀电流密度从大到小的顺序为:热影响区母材焊缝;焊接接头平均腐蚀速率在0.1~0.25 mm/a之间,硫化物浓度增加、pH值降低均可导致腐蚀速率增加;X65钢海管焊接接头在模拟现场工况条件下以均匀腐蚀为主,焊缝区腐蚀程度低于热影响区。

Influence of H2S Concentration and pH Value on Corrosion Behavior of Weld Joint of X65 Subsea Pipeline Steel

With an autoclave the environment of submarine gathering system was simulated, then in which the influence of concentration of H₂S and pH value on the corrosion behavior of weld joints of X65 pipeline steel was investigated by electrochemical techniques, immersion test, SEM and XRD analysis technique. The results show that the free corrosion potential of different portion of the X65 pipeline steel weld joint exhibited a tendency of decrease, but the corrosion density of increase, corresponding to the following order as: the weld seam, the heat affected zone and the base material. The average corrosion rate of the steel weld joints is in the range of 0.1~0.25 mm/a, the increase of the concentration of H₂S and the reduction of the pH value can both lead to the increase of corrosion rate. The corrosion mode of weld seam of X65 steel is mainly the uniform corrosion in the simulated environment, and the corrosion of weld seam is slighter than that of the heat affected zone.