Corrosion resistance of Fe-Si alloys in boiling sulfuric acid
Ioka Ikuo; Onuki Kaoru; Futakawa Masatoshi; Kuriki Yoshirou; Nagoshi Masayasu; Nakajima Hayato; Shimizu Saburo
Abstract:Corrosion behavior of Fe-Si alloys was examined in boiling environments of 95 wt% and 50 wt% sulfuric acid. The critical content of Si for the passivation was found to lie in the range of 9-10 wt% Si and 12-15 wt% Si in 95 wt% and 50 wt% sulfuric acid, respectively. The oxide film formed on the surface of the passivated alloys was examined by X-ray diffraction method and scanning Auger microscopy. The passivation film was composed of amorphous oxide with Si/O atomic ratio of about 0.5. The film contained a trace amount of sulfur when formed in oxidative 95 wt% sulfuric acid, whereas it did not when formed in reducing 50 wt% sulfuric acid. The film growth rate depended largely on the alloy composition and on the concentration of sulfuric acid as well. Key Words:corrosion, Fe-Si alloy, sulfuric acid, silicon oxide film, thermomechanical cycle, hydrogen production, water splitting