Electrolyte for micro-arc oxidation and method for dyeing substrate therein

Abstract

Disclosed is an electrolyte for micro-arc oxidation, which includes silicate, a fluoride, an alkali metal hydroxide, a pore modifier selected from at least one of triethanolamine and diethanolamine, and a polar solvent. Also disclosed is a method for dyeing a substrate which includes immersing a metal substrate as an anode into the electrolyte, oxidizing the substrate to form an oxide layer on the substrate, applying a solution containing a dye on the oxide layer, and allowing the dye to adhere on the oxide layer, so as to obtain a half-finished product, and forming a sealing layer on the half-finished product.

What is claimed is: 
     
         1 . An electrolyte used for micro-arc oxidation, comprising:
 a silicate;   a fluoride;   an alkali metal hydroxide;   a pore modifier selected from at least one of triethanolamine and diethanolamine; and   a polar solvent.   
     
     
         2 . The electrolyte used for micro-arc oxidation as claimed in  claim 1 , wherein said pore modifier has a concentration ranging between 0.1 g/L and 5 g/L. 
     
     
         3 . The electrolyte used for micro-arc oxidation as claimed in  claim 1 , wherein said silicate is selected from at least one of sodium silicate and potassium silicate. 
     
     
         4 . The electrolyte used for micro-arc oxidation as claimed in  claim 1 , wherein said fluoride is selected from at least one of sodium fluoride and potassium fluoride. 
     
     
         5 . The electrolyte used for micro-arc oxidation as claimed in  claim 1 , wherein said alkali metal hydroxide is selected from at least one of sodium hydroxide and potassium hydroxide. 
     
     
         6 . The electrolyte used for micro-arc oxidation as claimed in  claim 1 , wherein said silicate is selected from at least one of sodium silicate and potassium silicate, said fluoride is selected from at least one of sodium fluoride and potassium fluoride, and said alkali metal hydroxide is selected from at least one of sodium hydroxide and potassium hydroxide. 
     
     
         7 . The electrolyte used for micro-arc oxidation as claimed in  claim 1 , wherein said polar solvent is water. 
     
     
         8 . The electrolyte used for micro-arc oxidation as claimed in  claim 1 , wherein said electrolyte has a pH value greater than 7 and not greater than 11. 
     
     
         9 . A method for dyeing a substrate, comprising:
 providing a substrate made of magnesium or magnesium alloy;   immersing the substrate as an anode into the electrolyte as claimed in  claim 1 ;   oxidizing the substrate to form an oxide layer on the substrate, the oxide layer having a plurality of pores;   applying a solution containing a dye on the oxide layer, and allowing the dye to adhere on the oxide layer and to enter into at least a part of the pores, so as to obtain a half-finished product; and   forming a sealing layer on the half-finished product so that the sealing layer wraps the oxide layer and the dye.   
     
     
         10 . The method as claimed in  claim 9 , wherein oxidizing the substrate is conducted by micro-arc oxidation. 
     
     
         11 . The method as claimed in  claim 10 , wherein oxidizing the substrate is conducted in a voltage ranging between 450 V and 550 V, and an average current density across the substrate is 2 A/dm 2 . 
     
     
         12 . The method as claimed in  claim 9 , wherein in oxidizing the substrate, the electrolyte is maintained at a temperature ranging between 25° C. and 40° C. 
     
     
         13 . The method as claimed in  claim 9 , wherein oxidizing the substrate is carried out for a period not less than 10 minutes. 
     
     
         14 . The method as claimed in  claim 9 , wherein the oxide layer has a thickness not less than 10 μm, and the appearance of the oxide layer is white. 
     
     
         15 . The method as claimed in  claim 9 , wherein the pores have a pore size ranging from 10 μm to 25 μm. 
     
     
         16 . The method as claimed in  claim 9 , further comprising, after oxidizing the substrate, cleaning the substrate and the oxide layer so as to remove residue of the electrolyte. 
     
     
         17 . The method as claimed in  claim 9 , wherein forming the sealing layer is conducted by contacting the half-finished product with a sealing solution that contains nickel acetate at a temperature ranging from 25° C. to 35° C.