2009 Volume 50 Issue 7 Pages 1798-1804
Micro-contaminants on SUS304 stainless steel were observed and confirmed by atomic force microscope, and the micro-contaminant removal was carried out by ultraviolet (UV) illumination. With an increase in the holding time in air, particle- and film-like micro-contaminants appeared and their amount increased on the specimen surface. Then, the amount of particle-like contaminants decreased and finally almost all the surface was covered by film-like contaminants. The amount of micro-contaminants on the specimen surface decreased with an increase in the UV illumination time, with extensive removal of the organic substance in the contaminants but leaving part of the contained water in the contaminants. The micro-contaminants slowly re-adhered on the treated surface when the surface was re-exposed to air, with a longer period than 172 ks for the recovery to the state before the UV illumination. The surface for macro-droplets after the UV illumination became hydrophilic, while no large change of the wettability for micro-droplets on the same surface can be observed.