SUS304鋼に対する純水のミクロな濡れ性：塩水浸漬の影響

Abstract

The surface composition and micro-wettability of SUS304 steel by pure water before and after immersion in 3.5 mass% NaCl aqueous solution were investigated at room temperature. The surface composition was analyzed using X-ray photoelectron spectroscopy(XPS). Anode and cathode current distribution measurements on specimen surfaces in NaCl aqueous solution were performed with scanning vibration electrode equipment(SVE). The wetting morphologies of micro-pure water on specimen surfaces were observed and wettability was evaluated with an atomic force microscope(AFM) in AC non-contact mode. The relationship between micro-wetting behavior of pure water and the surface composition of SUS304 steel are discussed.The results obtained from XPS shows that considerable organic contamination is present on each surface, and oxides and hydroxides of iron, chromium and nickel formed on the specimen surfaces after wet polishing. The amount of oxide and hydroxide of chromium in the oxide (hydroxide) layer increased, while those of iron and nickel decreased after 1.8×106 s immersion in NaCl aqueous solution. The specimen surface became rougher after immersion, due to corrosion pitting. SVE measurements revealed that the ratio of anodic to cathodic area changed with immersion time, which indicates that oxides and hydroxides were resolved or formed, and local corrosion occurred. The AFM observation and evaluation showed that the wettability of SUS304 steel was reduced after immersion in NaCl solution.