The difference between aluminum oxidation organic dyeing and electrolytic coloring

Aluminum is a light, soft non-ferrous metal that is easily oxidized in the air, so people have come up with a solution, that is, the aluminum oxidation process, which grows a protective film on its outer layer, making it durable and dyed into colorful colors, pleasing to the eye.

The principle of aluminum anodizing is a process of making decorative and protective films on objects made of aluminum and its alloys. The manufacturing process of alumina film formed on aluminum is to pass through a suitable sulfuric acid electrolyte under sufficient voltage with direct current, in which the object aluminum is the anode, and another material (lead or special graphite plate) is used as the cathode, and the industrial aluminum profile is energized for a certain period of time to gradually grow the oxide film of the required thickness.

After the film is produced, in addition to some aluminum natural colors that do not need to be treated, the next step is to carry out coloring treatment, generally speaking, aluminum coloring is mainly divided into the following types:

1. Organic dyeing

2. Inorganic dyeing

3. Electrolytic coloring

4. Electroplating coloring

Below we mainly discuss the principles, advantages and disadvantages of commonly used organic dyeing and electrolytic coloring, as well as the product occasions used:

1. The electrolytic coloring film is based on the transparent anodized film of sulfuric acid primary electrolysis, and the oxide film (also called secondary electrolytic film) is electrolyzed in a solution containing metal salts (also called secondary electrolytic film). The weather resistance, light fastness and service life of the electrolytic coloring film are much better than that of the dyed film, and its energy consumption and coloring cost are much lower than that of the overall coloring film. At present, it is widely used in architectural aluminum profile coloring, but the color of electrolytic coloring is monotonous, usually only bronze, black, golden yellow, jujube red and so on. And the operation is not easy to control.

2. Organic dyeing, organic dyeing is based on the adsorption theory of substances, adsorption is divided into physical adsorption and chemical adsorption, and the physical adsorption of industrial aluminum profiles is the adsorption of molecules or ions in the form of electrostatic force; Chemisadption, the adsorption by chemical force, combines the two to produce organic dyeing, usually at a certain temperature. Due to the high porosity of the anodized film, strong adsorption capacity and easy organic dyeing, this method is fast coloring, bright color, easy to operate, after dyeing by sealing the hole, the dye can be firmly attached to the film pores, improve the anti-corrosion ability of the film layer, anti-fouling ability, until it can maintain a beautiful color, suitable for those that do not need to be used outdoors A large number of aluminum daily necessities, indoor aluminum industrial products and decorations, etc., the appearance is colorful and diverse. To meet people's interest in censorship and beauty pursuit in modern society, and to improve the competitive ability of the product market. Organic dyeing has some characteristics and requirements for oxide film:

1. The oxide film layer should have sufficient porosity

2. The inner wall of the membrane pore maintains a certain activity

3. The anodized film obtained from aluminum in sulfuric acid solution is colorless and porous, so it is most suitable for dyeing.

4. The oxide film layer must have a certain thickness, and the thinner film layer can only be dyed with a very light color

5. The hard anodized film is layered with chromic acid conventional oxide film, which is not suitable for organic dyeing

6. The oxide film layer should be complete and uniform, and there should be no scratches, sand holes, spot corrosion and other defects.

7. The film layer itself has a suitable color, and there is no difference in metallographic structure, such as grain size or severe segregation, so there are also certain requirements for aluminum alloy materials, when the content of silicon, magnesium, manganese, iron, copper, chromium, etc. in the alloy composition is too high, it often causes the oxide film to be dull, and the color changes will occur during dyeing.