Surface treatment process for aluminum alloy and aluminum alloy article thereof

Abstract

A surface treatment process for aluminum alloy includes the steps of: providing an aluminum alloy substrate containing silicon element; evenly distributing the silicon element in the substrate by solution treating the substrate; removing the silicon element at/near the surface of the substrate by acid treating the substrate; forming a porous aluminum oxide film on the substrate by anodizing the substrate; and staining the aluminum oxide film. An aluminum alloy article treated by the process is also described.

What is claimed is: 
     
         1 . A surface treatment process for aluminum alloy, comprising:
 providing an aluminum alloy substrate comprising silicon element;   evenly distributing the silicon element in the substrate by solution treating the substrate;   removing the silicon element at/near the surface of the substrate by acid treating the substrate;   forming a porous aluminum oxide film on the substrate by anodizing the substrate; and   staining the aluminum oxide film.   
     
     
         2 . The process as claimed in  claim 1 , wherein solution treating the substrate is carried out by positioning the substrate in a chamber type electrical resistance furnace having an inner temperature of about 495° C. to about 525° C. for about 8 hours to about 10 hours. 
     
     
         3 . The process as claimed in  claim 1 , wherein acid treating the substrate is carried out by dipping the substrate in an acid solution for about 5 min to about 10 min, the acid solution comprises nitric acid and hydrofluoric acid in a volume ratio of about 8-10:1-1.5. 
     
     
         4 . The process as claimed in  claim 3 , wherein after the acid treatment, the substrate comprises no silicon element from the surface of the substrate to the depth of about 15 μm to about 25 μm of the substrate, the total content of the silicon element contained in the substrate decreases about 1.3% to about 1.65%. 
     
     
         5 . The process as claimed in  claim 1 , wherein anodizing the substrate is carried out in a sulfuric solution having a concentration of about 120 g/L to about 210 g/L for about 5 min to about 65 min, the substrate acts as an anode, a stainless steel is provided and acts as a cathode, a voltage of about 20 V to about 60V is applied to the anode and cathode, producing an electric current of about 2 A/dm 2  to about 6.5 A/dm 2  in the sulfuric solution; wherein during the anodizing process, the sulfuric solution is kept at a temperature of about 3° C. to about 30° C. 
     
     
         6 . The process as claimed in  claim 5 , wherein the aluminum oxide film has a thickness of about 5 μm to about 12 μm, the aluminum oxide film defines a plurality of micro-pores, and comprises no silicon element. 
     
     
         7 . The process as claimed in  claim 1 , wherein staining the aluminum oxide film is carried out using a colorant having a concentration of about 0.2 g/L to about 4 g/L and a pH value of about 4-10, the colorant has a temperature of about 30° C. to about 60° C., staining the aluminum oxide film last about 5 min to about 20 min. 
     
     
         8 . The process as claimed in  claim 7 , wherein the colorant is xanthene dyes, methane dyes, coumarins dyes, cyanine dyes, stilbene dyes, or oxazine dyes. 
     
     
         9 . The process as claimed in  claim 7 , wherein the pH value of the colorant is adjusted using an acetic acid, ammonia water, or a sodium hydroxide. 
     
     
         10 . The process as claimed in  claim 1 , further comprising a sealing treatment to the aluminum oxide film using boiling water, vapor, nickel acetate, nickel sulfate, potassium dichromate, or stearic acid. 
     
     
         11 . The process as claimed in  claim 10 , wherein a hydrated aluminum oxide film is formed on the aluminum oxide film after the sealing treatment. 
     
     
         12 . The process as claimed in  claim 1 , further comprising a step of quenching the substrate after the substrate being solution treated, the quenching process is carried by dipping the substrate in water having a temperature of about 20° C. to about 25° C. for about 3 min to about 5 min. 
     
     
         13 . The process as claimed in  claim 1 , further comprising a step of chemical polishing the substrate before the substrate being anodized. 
     
     
         14 . The process as claimed in  claim 13 , wherein the chemical polishing process comprises the following steps: the substrate is dipped in a first polishing solution having a temperature of about 70° C. to about 90° C. for about 20 seconds to about 30 seconds, the first polishing solution comprises sulfuric acid and phosphoric acid in a volume ratio of about 1-1.5:3-5; the substrate is dipped in a second polishing solution having a temperature of about 60° C. to about 80° C. for about 20 seconds to about 30 seconds, the second polishing solution comprises nitric acid and phosphoric acid in a volume ratio of about 1-1.5:3-5. 
     
     
         15 . An aluminum alloy article, comprising:
 an aluminum alloy substrate, the substrate comprising no silicon element from the surface of the substrate to the depth of about 15 μm to about 25 μm of the substrate;   an porous aluminum oxide film disposed on the substrate, the aluminum oxide film comprising no silicon element, and defining a plurality of micro-pores; and   a hydrated aluminum oxide film disposed on the aluminum oxide film.   
     
     
         16 . The aluminum alloy article as claimed in  claim 15 , wherein the aluminum oxide film has a thickness of about 5 μm to about 12 μm.