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

Abstract

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% HNO 3 , 0.1 kmol･m -3 Na 2 MoO 4 -containing 30% HNO 3 , 3.5% H 2 O 2 and 0.98% H 2 O 2containing 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% HNO 3 or 0.1 kmol･m -3 Na 2 MoO 4 -containing 30% HNO 3 showed very good corrosion resistance against IPA corrosion. Heat-treatment at 200 ℃ after surface finishing using 30% HNO 3 and 0.1 kmol･m -3 Na 2 MoO 4 -containing 30% HNO 3 increased corrosion resistance against IPA. However, heat-treatment at temperatures higher than 350 ℃ decreased the corrosion resistance.