材料期刊网

采用动电位极化曲线, 电化学阻抗谱(EIS), SEM, XPS等分析手段研究了800合金在300 ℃ NaOH和乙醇胺(ETA)溶液中的腐蚀行为. 结果表明, ETA的添加降低合金的腐蚀电流密度, 增大了氧化膜的膜层电阻. 无论是否添加ETA, 800合金均为双层膜结构. 未添加ETA时,合金氧化膜外层富Ni, ETA添加后氧化膜外层富Cr. ETA的添加提高了氧化膜中Cr的富集程度, 促进了铬氧化物的形成, 增强了800合金氧化膜的保护性.

Many components in secondary side of pressurized water reactors (PWRs) are made of carbon steels and low alloy steels. The corrosion products produced by the flow accelerated corrosion (FAC) of these components can deposite on the surface of steam generator (SG) tubes and decrease the heat transfer efficiency of SG tubes. Moreover, the enrichment of foreign ions (e.g. Cl^- and Pb²⁺) occurs with the sedimentation of corrosion products and causes the local environment degradation, and thus accelerates the failure of SG tubes. In order to decrease the FAC of carbon steels and low alloy steels, pH controllers are often added to adjust the pH value of secondary water. The water chemistry environment of secondary side in PWRs has experienced various treatment techniques, such as phosphate treatment, all volatile treatment (AVT), morpholine (MPH) treatment, ethanolamine (ETA) treatment, and boric acid treatment. In comparision with AVT, ETA can significantly reduce the concentration of Fe in the steam-water phase region and water supply system because of its higher alkalinity and lower molar concentration in feedwater. Due to the high resistance to corrosion and stress corrosion cracking in high temperature and high pressure water, alloy 800 is often used as steam generator tubes in nuclear power plants and thus becomes increasingly attractive among researchers. However, few studies focus on the effect of ETA on the corrosion behavior of alloy 800 in high temperature and high pressure water. This work mainly aims to investigate the corrosion behavior of alloy 800 in NaOH and ETA solutions at 300 ℃ by potentiodynamic polarization curve, electrochemical impedance spectra (EIS), SEM and XPS. The electrochemical results demonstrate that the addition of ETA decreases the current density of anodic and cathodic reactions, and increases the corrosion potential of alloy 800. Besides, ETA addition significantly increases the resistance of inner oxide layer and makes the oxide film more compact, which increases the film resistance of alloy 800 in high temperature water. Through the morphology observation and composition analysis, it is found that ETA addition can promote the formation of Cr-rich layer and increase the ratio of chromium in the oxide films although the deposition of magnetite is enhanced on the surface of alloy 800. For stainless steels and nickel-based alloys in high temperature water, the Cr-rich oxide layer can inhibit the diffusion process of O and metal ions, and reduces the corrosion rates of alloys. Therefore, the corrosion resistance of alloy 800 is enhanced after ETA is added in high temperature water.