Outgassing Properties of 304 Stainless Steel Electropolished by Wiping Method

Surface and outgassing properties of 304 stainless steel samples were studied after electropolishing by a wiping method (WiEP) using felt that is attached to a cathode electrode and impregnated with an electrolyte. Surface morphology observed with an atomic force microscope suggests that WiEP yields a smoother surface with fewer pits compared with the conventional electropolishing method of immersing the samples in an electrolyte. The thickness of the oxide layer after either of the electropolishing processes was 3–4 nm as estimated by x-ray photoelectron spectroscopy, transmission electron microscopy, and energy-dispersive x-ray spectroscopy. Furthermore, no significant difference was found in the chemical state of the surface and oxide film in the two cases. Thermal desorption spectroscopy of the samples revealed that the amount of desorbed H2O and H2 was significantly low in the case of WiEP. The low outgassing was attributed to the formation of a smooth and dense oxide film on the sample surface after electropolishing by WiEP.