Chemical conversion reagent for magnesium alloy, surface-treating method, and magnesium alloy substrate

Abstract

The objective of the present invention is to impart coating film adhesion, corrosion resistance and rust prevention to magnesium alloys. A chemical conversion reagent for a magnesium alloy which comprises a phosphate ion and a permanganate ion and has pH of 1.5 to 7.

1 . A chemical conversion reagent for a magnesium alloy 
 which comprises a phosphate ion and a permanganate ion and    has pH of 1.5 to 7.    
     
     
         2 . The chemical conversion reagent for a magnesium alloy according to  claim 1   wherein the concentration of a compound serving as a source of the phosphate ion is 20 to 50 g/L and    the concentration of a compound serving as a source of the permanganate ion is 1 to 10 g/L.    
     
     
         3 . A surface-treating method 
 which comprises a step of bringing the chemical conversion reagent according to  claim 1  or  2  into contact with a magnesium alloy substrate.    
     
     
         4 . The surface-treating method according to  claim 3   wherein the magnesium alloy substrate is subjected to degreasing, pickling and desmutting treatments in advance.    
     
     
         5 . The surface-treating method according to  claim 4   wherein the pickling treatment is carried out with a reagent containing at least one member selected from the group consisting of sulfuric acid, nitric acid, phosphoric acid and a fluorine-containing compound.    
     
     
         6 . A magnesium alloy substrate obtainable by the surface-treating method according to any of  claims 3  to  5 .