Abstract:

With the widespread use of boric acid,the corrosion problem of equipments exposed to boric acid-containing medi-um 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-con-taining solution at a given temperature and a certain boron concentration was studied,and contrasting the vapor phase corro-sion 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.

Key words: austenitic stainless steel, boron-containing vapor, oxide film