PURPOSE: To maintain superior antibacterial characteristic over a long period without deteriorating characteristics, such as external appearance and workability, by regulating the Cu concentration in the surface layer part in the range between the position at a specific depth from the surface of a Cu-containing stainless steel and the surface.
CONSTITUTION: A martensitic stainless steel containing 0.01-5wt.% Cu is used as a base material, and the Cu concentration in the surface layer part between the surface and the position at a depth of 50 from the surface is regulated to ≥0.1 atomic %. A relationship of C1/C2=0.2 is established between the Cu concentration C1 in the surface layer part and the Cu content C2 in the steel as base material. The Cu concentration in the surface layer part can be increased to ≥0.1 atomic% by applying alternating electrolytic treatment to the stainless steel. By impressing a square-wave potential oscillating between the potential range baser than the passivating potential of Cr and the noble potential range from the natural potential of Fe to the passivation completing potential of Fe, the Cu ions eluted at the noble potential are precipitated in the steel surface at the base potential and the Cu concentration in the surface layer part can be increased.
UDAGAWA YOSHIKATSU
SAKAI TETSUO
FUKUMOTO HIROMITSU
