热挤压690合金管材在高温水中的长期均匀腐蚀行为

Long-term General Corrosion Behavior of Hot Extruded Tubing Alloy 690 in High Temperature Water

采用长期浸泡和表面膜俄歇电子能谱(AES)与扫描电子显微镜(SEM)分析方法研究了热挤压690合金管材3段不同挤出顺序的管段(头部A、中部B和尾部C)在高温除氧水中的均匀腐蚀行为与机理。结果表明:热挤压690合金管材头部A、中部B和尾部C 3种试样在浸泡2 500 h后均匀腐蚀均达到稳定状态,其均匀腐蚀速率均低于5 mg/(月·dm^2);头部A与尾部C的腐蚀速率相当,而明显低于中部B的腐蚀速率;氧化膜呈双层结构特征,即外层富Fe和Ni、内层富Ni和Cr,A与C试样氧化膜中间层存在铬壁垒,而B试样无明显的铬壁垒。

The general corrosion behavior and mechanism of three areas (namely head A, middle B and tail C) of hot extruded tubing alloy 690 in high temperature de-aerated water were studied by means of long-term immersion, and the oxide film was analyzed by Auger electron spectroscopy (AES) and scanning electron microscopy (SEM). The results show that the general corrosion process of A, B and C specimen reaches a stable state after immersion for 2 500 h, and their corrosion rates are all lower than 5 mg/(month·dm^2). The corrosion rate of head A is equal to that of tail C, and which are obviously lower than that of middle B. The oxide film is characterized by a double layer structure. The outer layer is rich in Fe and Ni, while the inner layer is rich in Ni and Cr. There is a chrome barrier in the middle of the oxide film of A and C specimen, however, the C specimen has no obvious chrome barrier.