Method for performing electropolishing treatment on aluminum material

Abstract

Provided is a method of performing electropolishing treatment on an aluminum material, which is capable of easily producing an aluminum material having an excellent outer appearance with luster and uniformity on an industrial scale. The method of performing electropolishing treatment on an aluminum material includes immersing the aluminum material in an electrolytic treatment solution in an electrolytic treatment tank, and applying an electrolysis voltage through use of the aluminum material as an anode, to thereby perform electropolishing treatment on a surface of the aluminum material, the method including: performing, as pretreatment for the electropolishing treatment, anodic oxidation treatment; performing, during the electropolishing treatment, bubble-diffusion-preventing treatment; and performing, as post-treatment for the electropolishing treatment, film peeling treatment for an electropolishing film.

1 . A method of performing electropolishing treatment on an aluminum material including immersing an aluminum material formed of aluminum or an aluminum alloy in an electrolytic treatment solution in an electrolytic treatment tank, and applying an electrolysis voltage through use of the aluminum material as an anode, to thereby perform electropolishing treatment on a surface of the aluminum material,
 the method comprising, as pretreatment for the electropolishing treatment, performing anodic oxidation treatment including subjecting the aluminum material to anodic oxidation in a pretreatment tank arranged separately from the electrolytic treatment tank at a voltage lower than the electrolysis voltage during the electropolishing treatment through use of a pretreatment solution formed of a polybasic acid aqueous solution having a weak ability to dissolve the aluminum material as compared to the electrolytic treatment solution, to thereby form an anodic oxide film on the surface of the aluminum material.   
     
     
         2 . A method of performing electropolishing treatment on an aluminum material including immersing an aluminum material formed of aluminum or an aluminum alloy in an electrolytic treatment solution in an electrolytic treatment tank, and applying an electrolysis voltage through use of the aluminum material as an anode, to thereby perform electropolishing treatment on a surface of the aluminum material,
 the electrolytic treatment tank comprising a cathode partition chamber which is formed of a material non-permeable to bubbles of hydrogen gas to be generated on a cathode serving as a counter electrode of the aluminum material and permeable to a liquid, is configured to partition the cathode from the aluminum material, and includes a discharge port for discharging the hydrogen gas out of the electrolytic treatment tank,   the method comprising, during the electropolishing treatment of the aluminum material, performing bubble-diffusion-preventing treatment including: preventing the bubbles of the hydrogen gas generated on the cathode in the cathode partition chamber from diffusing to an aluminum material side; and discharging the hydrogen gas out of the electrolytic treatment tank through the discharge port.   
     
     
         3 . A method of performing electropolishing treatment on an aluminum material including immersing an aluminum material formed of aluminum or an aluminum alloy in an electrolytic treatment solution in an electrolytic treatment tank, and applying an electrolysis voltage through use of the aluminum material as an anode, to thereby perform electropolishing treatment on a surface of the aluminum material,
 the method comprising, as post-treatment for the electropolishing treatment, performing film peeling treatment including immersing the aluminum material after the electropolishing treatment in a post-treatment solution formed of a sulfuric acid solution having a pH of 2 or less and containing sulfuric acid and an amine, to thereby dissolve and remove an electropolishing film present on the surface of the aluminum material.   
     
     
         4 . A method of performing electropolishing treatment on an aluminum material including immersing an aluminum material formed of aluminum or an aluminum alloy in an electrolytic treatment solution in an electrolytic treatment tank, and applying an electrolysis voltage through use of the aluminum material as an anode, to thereby perform electropolishing treatment on a surface of the aluminum material,
 the method comprising performing two or three treatments selected from the group consisting of i) an anodic oxidation treatment as a pretreatment, ii) a bubble-diffusion-preventing treatment during the electropolishing treatment, and iii) a film peeling treatment of an electropolishing film as a post-treatment, wherein   i) the anodic oxidation treatment includes subjecting the aluminum material to anodic oxidation in a pretreatment tank arranged separately from the electrolytic treatment tank at a voltage lower than the electrolysis voltage during the electropolishing treatment through use of a pretreatment solution formed of a polybasic acid aqueous solution having a weak ability to dissolve the aluminum material as compared to the electrolytic treatment solution, to thereby form an anodic oxide film on the surface of the aluminum material;   ii) the electrolytic treatment tank comprising a cathode partition chamber which is formed of a material non-permeable to bubbles of hydrogen gas to be generated on a cathode serving as a counter electrode of the aluminum material and permeable to a liquid, is configured to partition the cathode from the aluminum material, and includes a discharge port for discharging the hydrogen gas out of the electrolytic treatment tank, and   the bubble-diffusion-preventing treatment includes preventing the bubbles of the hydrogen gas generated on the cathode in the cathode partition chamber from diffusing to an aluminum material side, and discharging the hydrogen gas out of the electrolytic treatment tank through the discharge port; and   iii) the film peeling treatment includes immersing the aluminum material after the electropolishing treatment in a post-treatment solution formed of a sulfuric acid solution having a pH of 2 or less and containing sulfuric acid and an amine, to thereby dissolve and remove the electropolishing film present on the surface of the aluminum material.   
     
     
         5 . A method of performing electropolishing treatment on an aluminum material according to  claim 3  or  4 , wherein the post-treatment solution comprises a sulfuric acid solution obtained by dissolving a sulfate of an amine in water, a sulfuric acid solution obtained by dissolving sulfuric acid and an amine in water, a sulfuric acid solution obtained by dissolving sulfuric acid, an amine, and a sulfate of an amine in water, or a sulfuric acid solution obtained by dissolving amidosulfuric acid or an ammonium salt thereof in water. 
     
     
         6 . A method of performing electropolishing treatment on an aluminum material according to  claim 5 , wherein the sulfuric acid solution to be used as the post-treatment solution comprises an aqueous solution of amidosulfuric acid.