ATOMIC IMAGES OF 304SS SURFACE AFTER ELECTROCHEMICAL TREATMENTS

Sputter-deposited 304 stainless steel was electrochemically treated in 0.1 M H2SO4 aqueous solution, and was observed in air at atomic resol ution with a scanning tunneling microscope. After passivation for 15 m in at 400 mV (SCE), there was initially little order present, but the diameter of oxide particles (grains or partly ordered domains) increas ed from about 30 to 200 nm during 3 h after the treatment, Surface ato ms of oxygen or hydroxyl gradually become ordered in air and the struc ture of the substrate surface becomes apparent on the surface of the p assive film. This suggests that the surface is covered with a single o xide phase, which is initially rather disordered but crystallizes with time. (C) 1997 Elsevier Science B.V.