Method of salt bath nitriding for producing iron member having improved corrosion resistance and iron parts

A new nitriding process by using a salt bath to produce iron and steel parts having excellent abrasion resistance and corrosion resistance are explained. A iron lithium complex oxide layer are formed at the outermost surface of the iron part by immersing the iron and steel parts in a salt bath containing cationic component of Li, Na and K and anionic components of CNO − and CO 3 2− , where hydroxide compound selected from lithium hydroxide, sodium hydroxide and potassium hydroxide are added to the salt bath. Materials being in a hydrated state or in a free water containing state can be used for preparation or replenishing of the salt bath. An moistend air of (1×10 −2 kg·H 2 O)/(1 kg dry air) can be used for mixing the salt bath. Containing ratio of Li, Na, K is preferable where a solidifying temperature of the mixture of carbonates of Li, Na, K in that ratio is lower than 500° C. It is preferable that the mol ratio of Na and K is to be 2:8˜8:2, the content of CNO − is to be 5˜35 wt %, the content of CN − in the salt bath is less than 2 wt % and the temperature of the salt bath is to be 450˜650° C.