イソプロピルアルコール中での電解研磨SUS316Lステンレス鋼の局部腐食とその防止のための表面処理法

抄録

This study developed surface finishing methods to prevent corrosion of electropolished SUS316L stainless steel in isopropyl alcohol（IPA）. For this development, immersion corrosion tests in 99.7% IPA and anodic polarization tests in 0.15 kmol･m^－3 HCl were conducted using electropolished SUS316L specimens passivated with 30% HNO₃, 0.1 kmol･m^－3 Na₂MoO₄-containing 30% HNO₃, 3.5% H₂O₂ and 0.98% H₂O₂- containing 8% citric acid. Identical tests were also applied to specimens heated to 200－450 ℃ after passivation treatments. Corrosion morphologies of these specimens in 99.7% IPA exhibited pitting. Pit densities and corrosion rates of these specimens in 99.7% IPA showed good correlation with pitting potentials in 0.15 kmol･m^－3 HCl. Judging from the obtained values of pit densities and pitting potentials, specimens passivated with 30% HNO₃ or 0.1 kmol･m^－3 Na₂MoO₄-containing 30% HNO₃ showed very good corrosion resistance against IPA corrosion. Heat-treatment at 200 ℃ after surface finishing using 30% HNO₃ and 0.1 kmol･m^－3 Na₂MoO₄-containing 30% HNO₃ increased corrosion resistance against IPA. However, heat-treatment at temperatures higher than 350 ℃ decreased the corrosion resistance.