核电汽轮机焊接转子接头在氯离子环境中的电偶腐蚀行为

Galvanic corrosion behavior of nuclear steam turbine welded joint in chloride environment

为了研究焊接接头的尺寸效应对焊接接头的电偶腐蚀行为的影响,采用宏观电化学、微区电化学(SVET)、浸泡试验等试验研究了25Cr2Ni2MoV转子钢焊接接头在氯离子溶液中的电偶腐蚀行为.结果表明,焊缝的腐蚀电位最低,腐蚀电流密度最大,焊缝区作为阳极优先发生腐蚀,而母材和热影响区作为阴极区被保护.进一步运用三维形貌仪(IFM)和扫描电镜(SEM)观察腐蚀表面形貌,发现随着焊接接头尺寸的增加电偶腐蚀效应更显著,但是当接头尺寸增大到一定程度后,电偶腐蚀效应又有所减弱.

To investigate the effect of geometry of welded joint on the galvanic corrosion behavior,the macroscopic electrochemical experiments,scanning vibrating electrode technique (SVET) and immersion tests were used to study the galvanic corrosion behavior of welded joint of 25Cr2Ni2MoV rotor steel in the chloride solution.The results indicate that the corrosion potential of the WM is the lowest and the corrosion current density is the highest.That is to say,the WM is the anodic region which is prior to be corroded while the BM and the HAZ are the cathodic region which are protected.The infinite focus microscope (IFM) and scanning electron microscope (SEM) were used to further observe the morphology of the specimen surfaces.It is found that the effect of galvanic corrosion is more significant with the increase of welded joint size,but when the joint size increases to a certain extent,the galvanic corrosion effect is weakened.