Method to increase corrosion resistance in ferritic nitrocarburized treated cast iron substrates

Abstract

A method for improving corrosion resistance in FNC cast iron substrates without the need for additional coating or painting. The exemplary methods remove a portion of the FNC coating applied to a cast iron substrate, preferably through polishing, to expose the epsilon phase portion of the compound area. The epsilon phase portion is thought to provide improved corrosion protection as compared to non-polished FNC cast iron substrates. One exemplary product that may be provided with improved corrosion protection according to the above method is a brake rotor having a FNC treatment.

1 . A method for improving corrosion resistance for a cast iron substrate including a nitrocarburized surface treatment, the method comprising:
 applying the nitrocarburized surface treatment to an outer surface of the cast iron substrate to a predetermined depth, the applied nitrocarburized surface treatment including a compound area having a predetermined depth extending from said outer surface; and   removing a portion of said predetermined depth of said compound area to expose a dominant epsilon phase portion.   
     
     
         2 . The method of  claim 1 , wherein removing a portion of said compound area comprises grinding said compound area. 
     
     
         3 . The method of  claim 2 , wherein grinding said compound area comprising grinding said compound area with a diamond paste having diamond particles of approximately 1 micron in diameter. 
     
     
         4 . The method of  claim 1 , wherein removing a portion of said compound area comprises polishing said compound area. 
     
     
         5 . The method of  claim 4 , wherein polishing said compound area comprising polishing said compound area with a diamond paste having diamond particles of approximately 1 micron in diameter. 
     
     
         6 . The method of  claim 1 , wherein removing a portion of said compound area comprises conditioning said compound area. 
     
     
         7 . The method of  claim 6 , wherein conditioning said compound area comprising conditioning said compound area with a diamond paste having diamond particles of approximately 1 micron in diameter. 
     
     
         8 . The method of  claim 1 , wherein said dominant epsilon phase portion is located between about 2 and 6 microns from an outer surface of said nitrocarburized surface treatment, wherein said predetermined depth is between about 10 and 20 microns. 
     
     
         9 . A product including the cast iron substrate formed according to the method of  claim 1 . 
     
     
         10 . The method of  claim 9 , wherein said product comprises a brake rotor. 
     
     
         11 . The method of  claim 10 , wherein removing a portion of said predetermined depth of said compound area to expose a dominant epsilon phase portion comprises removing a portion of said predetermined depth of said compound area of a non-frictional surface of said brake rotor to expose a dominant epsilon phase portion. 
     
     
         12 . The method of  claim 11 , wherein said non-frictional surface comprises a hat portion of a brake rotor. 
     
     
         13 . A method for improving corrosion resistance for a brake rotor, the method comprising:
 applying a nitrocarburized surface treatment to an outer surface of the brake rotor to a predetermined depth, said applied nitrocarburized surface treatment forming a compound area having a predetermined depth extending from said outer surface; and   removing a portion of said predetermined depth of said compound area in a non-frictional area of the brake rotor to expose a dominant epsilon phase portion.   
     
     
         14 . The method of  claim 13 , wherein removing a portion of said compound area within said non-frictional area comprises grinding, conditioning or polishing said compound area to expose a dominant epsilon phase portion. 
     
     
         15 . The method of  claim 14 , wherein grinding, conditioning or polishing said compound area comprises grinding said compound area with a diamond paste having diamond particles of approximately 1 micron in diameter. 
     
     
         16 . The method of  claim 14 , wherein grinding, conditioning or polishing said compound area comprises conditioning said compound area with a diamond paste having diamond particles of approximately 1 micron in diameter. 
     
     
         17 . The method of  claim 14 , wherein grinding, conditioning or polishing said compound area comprises polishing said compound area with a diamond paste having diamond particles of approximately 1 micron in diameter. 
     
     
         18 . The method of  claim 13 , wherein said dominant epsilon phase portion is located between about 2 and 6 microns from an outer surface of said nitrocarburized surface treatment, wherein said predetermined depth is between about 10 and 20 microns. 
     
     
         19 . The method of  claim 13 , wherein said non-frictional area comprises a hat portion of the brake rotor. 
     
     
         20 . The method of  claim 13 , wherein said removed portion of said compound area comprises a mix of gamma phase, epsilon phase and iron oxides.