Patent ID: 7217327
Filing Date: 2007-05-15
Classification: C23C

Abstract:
1. A method of producing a metal member with enhanced corrosion resistance by salt bath nitriding, said method including forming a nitrided layer on a surface of said metal member and concurrently, an oxide film on an outermost layer of said nitrided layer by immersing said metal member in a nitriding salt bath containing Li which comprises, as a subsequent step to said immersion in said nitriding salt bath, immersing said metal member in a displacement cleansing salt bath, wherein the displacement cleansing salt bath is obtained by adding an alkali metal hydroxide and an alkali metal nitrite into a salt bath containing primarily at least one member selected from the group consisting of sodium nitrate, potassium nitrate and lithium nitrate, so that the displacement cleansing salt bath comprises the alkali metal hydroxide, from 43 to 45 wt % of alkali metal nitrite and from 52 to 55 wt % of alkali metal nitrate; the alkali metal hydroxide is at least one member selected from the group consisting of sodium hydroxide, potassium hydroxide and lithium hydroxide; and the alkali metal nitrite is at least one member selected from the group consisting of sodium nitrite, potassium nitrite and lithium nitrite.