Aluminum is a light, soft non-ferrous metal, easily oxidized in the air, so people came up with a method, that is, aluminum oxidation process, the outer layer of the growth of protective film, make it durable, and can be dyed into colorful colors, pleasing to the eye.
The principle of aluminum anodizing is a process of forming decorative and protective films on objects made of aluminum and its alloys. The production process of alumina film formed on aluminum is by direct current under sufficient voltage through a suitable sulfuric acid electrolyte, in which aluminum is the anode, and another material (lead or special graphite plate) as the cathode, industrial aluminum profile electricity for a certain period of time to gradually grow the required thickness of the oxide film.
After the film is produced, in addition to some aluminum color does not need to be treated, the next step is to carry out coloring treatment. Generally speaking, the coloring of aluminum is mainly divided into the following types:
1. Organic dye
2. Inorganic dyeing
3. Electrolytic coloring
4. Electroplating tinting
Here we mainly discuss the principle, advantages and disadvantages of common organic dyeing and electrolytic coloring, as well as the product occasions used:
1. The electrolytic coloring film is based on the transparent anodic oxide film of sulfuric acid primary electrolysis. In the solution containing metal salts, the electrolytic coloring film (also known as the secondary electrolytic film) has much better weather resistance, light resistance and service life than the dyeing film, and its energy consumption and coloring cost are far lower than the overall coloring film. At present, it is widely used for building aluminum profile coloring, but the color of electrolytic coloring is monotonous, usually only bronze, black, golden, jujube red and so on. And the operation is not easy to control.
2. Organic dyeing, organic dyeing based on the adsorption theory of substances, adsorption can be divided into physical adsorption and chemical adsorption, physical adsorption of industrial aluminum profiles is the adsorption of molecules or ions by electrostatic force; Chemorption, adsorption by chemical forces, which combine to produce organic staining, usually at a certain temperature. Due to their high anodic oxidation film porosity, adsorption ability to organic dyes, this method color fast, bright color, easy to operate, the hole sealing treatment after dyeing, the dye can firmly adhere to the membrane pores, improve the anticorrosive ability of the film, fight corrupt ability, until can keep beautiful color, suitable for outdoor use for those who do not need to a large number of aluminum products, Interior with aluminum industrial products and decorations, the appearance of a variety of colors. Meet the modern society people review and pursue beauty interest, improve the competitive ability of the product market. Organic dyeing has some characteristics and requirements for oxide film:
1. The oxide film should have sufficient porosity
2. The inner wall of the membrane hole maintains certain activity
3. The anodized film obtained from aluminum in sulfuric acid solution is colorless and porous, so it is most suitable for staining.
4. The oxide film must have a certain thickness, and the thinner film can only be stained with a very light color
5. Hard anodic oxide film with chromic acid conventional oxide film is not suitable for organic dyeing
6. The oxide film should be complete and uniform, without scratches, trachoma, spot corrosion and other defects.
7. The film layer itself has the right color, and there is no difference in metallographic structure, such as grain size or serious segregation, so there are certain requirements for aluminum alloy materials, alloy components of silicon, magnesium, manganese, iron, copper, chromium and other content is too high, often cause the oxide film dark matte, when the color changes.
