含硼水溶液上方蒸汽对奥氏体不锈钢的腐蚀行为

Corrosion behavior of austenitic stainless steel exposed to the vapor above boron-containing solution

硼酸应用广泛,其对设备腐蚀不容忽视。针对核电站含硼水溶液循环体系中设备顶端腐蚀的实际情况,取304奥氏体不锈钢为研究对象,研究了在给定温度和一定硼浓度水溶液存在下,溶液上方含硼水蒸气对奥氏体不锈钢的腐蚀行为,并将其与相应的溶液腐蚀对比。采用扫描电子显微镜(SEM)、X射线衍射仪(XRD)和X射线光电子能谱仪(XPS)分析了试样表面氧化膜。结果表明:在180℃下腐蚀1 200 h后,304不锈钢在含硼水蒸气中的腐蚀程度高于相应含硼水溶液的腐蚀程度;尽管两种环境中的试样表面均形成了双层氧化膜,但在含硼水蒸气中形成的氧化膜表层富铁镍,而在含硼水溶液中形成的氧化膜表层富铬,并用氧化膜形成机理解释了此现象。

With the widespread use of boric acid,the corrosion problem of equipments exposed to boric acid-containing medium cannot be ignored.Based on the actual situation of the equipment tip corrosion in the boron-containing solution circulating system of nuclear power plant,the corrosion behavior of 304 austenitic stainless steel exposed to the vapor above boron-containing solution at a given temperature and a certain boron concentration was studied,and contrasting the vapor phase corrosion with the corresponding solution corrosion was also discussed.The oxide films formed on the surface of specimens were characterized by scanning electron microscopy(SEM),X-ray diffraction(XRD) and X-ray photoelectron spectroscopy(XPS).The result indicated that the corrosion of 304 stainless steel exposed to boron-containing vapor was more serious than that exposed to boron-containing solution at 180 ℃ when the corrosion test was carried out for 1 200 h.In spite of forming double-layer oxide films on the samples in both boron-containing vapor and solution,it was noted that the surface layer of the oxide film formed in boron-containing vapor was rich in Fe and Ni,while the surface layer of the oxide film formed in boron-containing solution was rich in Cr.This phenomenon was elucidated by the formation mechanism of oxide film.