| 摘要 |
PURPOSE:To impart a composite material with excellent corrosion resistance as well as wear resistance by subjecting the surface of a ferrous material subjected to nitriding treatment to oxidizing treatment under specified conditions to modify the surface part and forming an iron oxide contg. layer thereon. CONSTITUTION:The surface of a ferrous metallic material is subjected to nitriding treatment to form an iron-nitrogen compound contg. layer. This layer is subjected to oxidizing treatment at 110 to 140 deg.C by using a treating bath constituted of an aq. soln. contg. sodium hydroxide, sodium nitrate and sodium sulfite. By this treatment, at least the surface part of the iron-nitroten contg. layer is modified. Furthermore, an iron oxide-contg. layer is formed thereon. As for the compsn. of the treating soln., preferably, the concn. of sodium hydroxide is regulated to, by weight, 25 to 55%, that of sodium nitrate to 10 to 25% and that of sodium sulfite to 5 to 15%. The thickness of the iron-nitrogen compound contg. layer is preferably regulated to 10 to 20mum. The formed composite layer has excellent corrosion resistance and furthermore small in dispersion in the corrosion resistance.
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