Aluminum alloy surface hardening treatment Aluminum alloy surface hardening treatment

Oxidation treatment technical description:

1. Chemical oxidation

The film obtained by chemical oxidation treatment is relatively thin, the general thickness is 0.5μm ~ 4μm, the quality is soft and not wear-resistant, and the corrosion resistance is lower than that of anodic oxidation film. Generally should not be used alone, due to the chemical oxidation film adsorption capacity is good, mainly acting on the bottom of the paint, chemical oxidation according to its solution can be divided into alkaline and acidic two. According to its film properties can be divided into oxide film, phosphate film, chromate film and phosphate chromate film, etc. (This type of oxide film is conductive)

2. Electrochemical oxidation

Electrochemical oxidation (commonly known as anodizing) is aluminum and aluminum alloys in the corresponding electrolyte and specific process conditions, due to the role of impressed current. The process of forming an oxide film on aluminum and aluminum alloys is called anodizing (this oxide film is not conductive).

3. Hard anodizing

The formation mechanism of the hard oxide film is the same as that of ordinary sulfuric acid anodizing, but in order to obtain a thick and hard film layer, it is necessary to use an electrolyte of about 0 degrees Celsius, and a method of high voltage and high current, so that the formation rate of the film is much higher than the dissolution rate, and the structure of the film changes, which constitutes a new feature of the growth process of the hard oxide film. The hard oxide film is also a double-layer structure, the difference is that the thickness of the barrier layer is 10 times larger than that of the ordinary oxide film, and the hole wall is also so, which is one of the basic reasons for the high hardness. However, the porosity is 7 ~ 8 times less than that of ordinary oxide film. Only 2% to 6%, the hard film base group is disorderly and interferes with each other, and a special prismatic shape appears. Resulting in large stress in the film, even causing cracking, residual alloy elements and electrolytic decomposition products in the film wall. The color of the oxide film is dark and the color of the alloy composition is different. Alloy composition and impurities have a greater impact on hard oxidation, which affects the uniformity and integrity of the oxide film, aluminum copper, aluminum silicon. Hard oxidation of aluminum alloys is difficult.

4. Structure of aluminum anodized film.

The oxide film is composed of a barrier layer and a porous layer, which is composed of a number of oxide base groups (membrane cells) with hexagonal columns, each with a hexagonal small hole in the center of the membrane cell. Shaped like a honeycomb structure, the thickness of the pore wall is twice the diameter of the pore. The average porosity of the sulfuric acid anodized film is 20% to 30%, and there are about 800 small holes on the surface of 1μm2, so it can wear various colors after anodizing.

5. Coloring of anodic oxide film

The anodized film is porous and chemically active, making it easy to dye. The aluminum oxide film has 20% to 30% of the pores (sulfuric acid film), so it has a huge specific surface area of chemical activity, and dye molecules are deposited in the inner surface layer through the physical and chemical adsorption of the oxide film. The porosity of the hard oxide film is less than that of the ordinary oxide film, the hole depth is small, the coloring is difficult than that of the ordinary oxide film, and the hard oxide film is a thick film due to the difference of the alloy. Its background color is relatively deep, so the coloring can only be more ideal with black.

6. Sealing treatment after anodizing

Aluminum anodized film has a high porosity, and adsorption capacity, easy to be polluted and corroded, medium corrosion, therefore, whether the oxide film is colored or not, for what occasion, must be closed treatment, its purpose is to improve corrosion resistance. Improve the anti-pollution ability and fixed pigment bodies, if there is a special follow-up treatment can not be closed, increase the adsorption capacity.