Effect of electropolishing on corrosion of Alloy 600 in high temperature water

Effect of change in surface composition and microstructure by electropolishing on corrosion of Alloy 600 in high temperature water was investigated. The investigation was conducted by comparing the corrosion of electropolished surface (EPS) with that of the 40 nm-colloidal silica slurry polished surface (CPS), which has few composition change as well as few surface residual strain. The result revealed while EPS had a thicker oxide scale at the early stage of corrosion, it showed a lower corrosion rate when the exposure time was >25 h. This is attributed to formation of a Cr-enriched oxide film at the primary surface by electropolishing.