A method for forming an oxidation-passive layer having high corrosion resistance to highly oxidizing materials such as ozone; a stainless steel and a titanium base alloy having corrosion resistance to an ozone containing fluid; and a fluid containing part, a process apparatus, and a fluid feed/discharge system made by using the same. The method comprises the steps of heat-treating the surface of a stainless steel or titanium-base alloy having an Al content of 0.5 percent by weight to 7 percent by weight either at 300° C. to 700° C. in a mixed gas atmosphere composed of an inert gas and 500 ppb to 1 percent H2O gas or 1 ppm to 500 ppm oxygen gas, or alternatively at 20° C. to 300° C. in a mixed gas atmosphere composed of an oxygen gas and at least 100 ppm ozone gas to form an oxidation-passive layer containing an aluminum oxide or a titanium oxide.