X65钢焊接接头在模拟浅表海水和深海环境中的腐蚀行为对比

在实验室模拟条件下,采用失重法及电化学等方法并结合腐蚀形貌显微观察,研究了X65钢焊接接头在浅表海水和深海(1000 m)环境中的短期腐蚀行为及其机理。结果表明,X65钢焊接接头在浅表海水环境下的腐蚀速率大于深海环境下的腐蚀速率,浅表海水环境以点蚀为主,深海环境只在熔合线附近腐蚀相对较快,焊缝区腐蚀不明显;在模拟浅表海水和深海环境下,热影响区(HAZ)的腐蚀电位均低于焊缝和母材区,导致焊缝区域存在电偶效应,加速了HAZ的腐蚀,形成较厚的腐蚀产物膜。

Comparative Study on Corrosion of X65 Pipeline Steel Welded Joint in Simulated Shallow and Deep Sea Environment

The short-term corrosion behavior of the welded joint of X65 pipeline steel was comparatively studied in artificial laboratory environments, which aims to simulate the real environment of shallow and deep sea respectively, by using mass loss test, potentiodynamic polarization curve measurement and corrosion morphological observation by scanning electron microscopy (SEM). Results show that the corrosion rate of the welded joint in simulated shallow sea water was faster than that in the simulated deep sea environment. In the simulated shallow sea environment the weld joint exhibited mainly pitting corrosion; however in the simulated deep sea environment, relatively serious corrosion occurred near the fusion-line (FL) while non obvious corrosion could be observed on the welded zone. The corrosion potential of heat affected zone (HAZ) was lower than that of the welded zone and matrix of X65 pipeline steel both in simulated deep and shallow sea environments, which caused galvanic effect in welded zone and accelerated the corrosion rate of HAZ. Thereby the formed corrosion product film on HAZ was thicker with a larger charge-transfer resistance R_t.