The processing of aluminum die-casting parts adopts artificial methods to form an oxide film on the surface of aluminum and its alloy products and apply different colors to improve the wear resistance of aluminum materials, prolong the service life and increase the appearance of color and luster. The basic process of oxidative coloring is aluminum surface treatment, oxidation, coloring and subsequent hydration sealing, organic coating and other treatment processes.
Oxidation of aluminum: The surface of aluminum maintains a layer of oxide film of 10 to 100 angstroms under natural conditions, and the artificial oxide film is controlled to a thickness of 0.5 to 250 microns according to different purposes. The methods of artificial membrane generation include chemical oxidation and electrochemical oxidation.
Chemical oxidation: The aluminum or aluminum alloy after surface purification treatment is chemically reacted in an oxidizing solution containing an oxidant and an activator to form an oxide film. The function of the activator is to partially dissolve the oxide film during the formation process, resulting in pores, so that the oxidation can continue and the oxide film can be thickened.
Anodizing: Usually carried out in electrolyte solutions such as sulfuric acid, oxalic acid or chromic acid. With aluminum as the anode, lead and other metals as the cathode, under the action of the DC electric field, the anion moves to the anode, and the new oxygen is generated at the anode to interact with the aluminum as the anode to form an oxide film.
Chemical coloring: The oxidized aluminum material is immersed in an organic or inorganic dye solution, and the dye penetrates into the pores of the oxide film and is colored by chemical or physical action.
Electrolytic coloring: The oxidized aluminum material is subjected to secondary electrolysis in a single metal salt or multiple metal salt aqueous solution. Under the action of an electric field, metal cations penetrate into the pores of the oxide film and deposit on the bottom of the pores, thereby causing oxidation Films produce bronze, brown, gray, and shades of red, cyan, and blue.