The difference between aluminum oxide organic dyeing and electrolytic dyeing

Aluminum is a light and soft non-ferrous metal, which is easily oxidized in the air, so people came up with a method, that is, aluminum oxidation process, which grows a protective film on its outer layer to make it durable and can be dyed into colorful 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 aluminum oxide film formed on aluminum is made by passing a suitable sulfuric acid electrolyte through direct current at a sufficient voltage, where the object aluminum is the anode, and another material (lead or special graphite plate) is used as the cathode. The oxide film of the required thickness is gradually grown after electrifying for a certain period of time.

After the film is produced, the next step is to carry out the coloring process, except for some of the natural color of aluminum that does not need to be processed. Generally speaking, the coloring of aluminum 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 dyeing, as well as the product occasions used:

1. The electrolytic colored film is based on the transparent anodic oxide film produced by the primary electrolysis of sulfuric acid. The electrolytic colored oxide film (also called the secondary electrolytic film) is electrolytically colored in a solution containing metal salt in a solution containing metal salts. The weather resistance and light resistance of the electrolytic colored film And the service life is much better than that of dyed film, and its energy consumption and coloring cost are much lower than that of overall dyed film. At present, it is widely used for the coloring of architectural aluminum profiles, but the electrolytic coloring has a monotonous tone, usually only bronze, black, golden yellow, maroon and so on. And the operation is not easy to control.

2. Organic dyeing. Organic dyeing is based on the adsorption theory of substances. There are physical adsorption and chemical adsorption. Physical adsorption is the adsorption of molecules or ions by electrostatic force; chemical adsorption, adsorption by chemical force, a combination of the two To produce organic dyeing, usually at a certain temperature. Because the anodic oxide film has high porosity and strong adsorption capacity, it is easy to dye organically. This method has fast coloring, bright color and easy operation. After dyeing, the dye can be firmly attached to the pores of the film, which improves the film’s performance. Anti-corrosion ability, anti-fouling ability, until it can maintain beautiful color, it is suitable for a large number of aluminum daily necessities that do not need outdoor use, indoor aluminum industrial products and decorations, etc., and the appearance is colorful and diverse. Satisfy people's interest in censorship and pursuit of beauty in modern society, and improve the competitiveness of the product market. Organic dyeing has some characteristics and requirements for oxide film:

1. The oxide film layer must have sufficient porosity.

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

3. The anodic oxide film of 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 anodic oxide film uses 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 defects such as scratches, blisters, and pitting corrosion.

 7. The film itself has the appropriate color and there is no difference in the metallographic structure, such as different grain sizes or severe segregation. Therefore, there are certain requirements for aluminum alloy materials. The alloy composition includes silicon, magnesium, manganese, iron, When the content of copper, chromium, etc. is too high, it will often cause the oxide film to be dull, and the color tone will change during dyeing.