Method for producing highly corrosion-resistant colored article made of steel

Abstract

The present invention provides a method for producing a highly corrosion-resistant colored article made of steel, which are highly corrosion-resistant and has a variety of vivid surface colors, by subjecting the surface of a nitrided steel article to oxidizing heat treatment to form a colored oxide film layer. The method for producing a highly corrosion-resistant colored article made of steel includes the steps of (a) subjecting an article made of steel to nitriding and (b) subjecting the steel article thus treated in step (a) to surface processing such as abrasion, buffing, polishing or the like, and then to oxidizing heat treatment in an oxidizing atmosphere at 100 to 700° C. for 30 seconds to 100 hours, to form a colored oxide film layer on the surface of the steel article.

1 . A method for producing a highly corrosion-resistant colored article made of steel, the method comprising the steps of:
 (a) subjecting an article made of steel to nitriding and then to abrasion; and   (b) subjecting the steel article thus treated in step (a) to oxidizing heat treatment in an oxidizing atmosphere at 100 to 700° C. for 30 seconds to 100 hours, to form a colored oxide film layer on the surface of the steel article.   
   
   
       2 . The method according to  claim 1 , wherein the oxidizing atmosphere comprises oxygen, air, carbon dioxide or steam, either individually or as a mixture of two or more species. 
   
   
       3 . The method according to  claim 1 , wherein the process of abrasion is performed by any one selected from buffing, lapping, abrading and polishing. 
   
   
       4 . The method according to  claim 1 , wherein the heat treatment used for the nitriding or oxidizing heat treatment is performed using any one selected from a pit type furnace equipped with stirring fans at the top and the bottom and having gas introduced at the top or the bottom, a sealed quench furnace, a fluidized bed furnace, a meshbelt type continuous furnace consisting of three or more chambers respectively equipped with stirring fans at the top and the bottom, a salt bath furnace, a plasma furnace, and a high frequency induction furnace.