Surface characteristics of AISI 304L stainless steel after an atmospheric pressure plasma treatment

AISI 304L stainless steel plates were treated in an atmospheric pressure plasma at room temperature in order to improve the surface properties. After plasma treatment, the contact angle test was conducted and the wettability and the surface-free energy of the stainless steel plates were both proved to be enhanced after plasma treatment. Through the analysis of the contact angle and surface-free energy, the optimum plasma treatment conditions were also obtained, including the treatment time of 60 s, the treatment power of 120 W and the aging time of 3 to 5 min in air. In the meanwhile, the surface roughness, morphology and chemical compositions of the stainless steel plates before and after plasma treatment were characterized by atomic force microscopy (AFM) and X-ray Photoelectron Spectroscopy (XPS). It was proved that the surface roughness was slightly decreased, and new functional groups-oxides and nitrides, appeared on the surface of the stainless steel after plasma treatment.