TREATMENT LIQUID FOR FORMING PROTECTIVE FILM FOR STEEL MEMBER HAVING NITROGEN COMPOUND LAYER, AND COMPOUND LAYER PROTECTIVE FILM

摘要

Disclosed is a means for preventing oxidation of a compound layer by high-frequency hardening, said compound layer having been formed on the surface of a steel material by nitriding. Specifically disclosed is a treatment liquid for forming a compound layer protective film, which is a treatment liquid for forming a protective layer on a nitride layer for the purpose of protecting the nitride, said nitride layer having been formed on a steel material after nitriding. The treatment liquid for forming a compound layer protective film is characterized by containing at least one element selected from the group consisting of Si, Ti, Zr, Hf, V, Ta, Ca, Ce, Sc, Nb, Cr, W, Al, Sr, Zn, Mg and Mo, and containing 0.1-60 g/L of at least one kind of anions selected from the group consisting of phosphate ions, condensed phosphate ions, phosphite ions, fluoride ions, carbonate ions and silicate ions. The treatment liquid for forming a compound layer protective film is also characterized by having a pH of 4-14.