metal or alloy article is used as an anode, and an oxide film is formed on its surface by electrolysis. Metal oxide films change the surface state and properties, such as surface coloration, increase corrosion resistance, enhance wear resistance and hardness, and protect metal surfaces.

For example, aluminium anodization,
aluminium and aluminium alloys are placed in the corresponding electrolyte (such as sulfuric acid, chromic acid, oxalic acid, etc.) as the anode, and electrolysis is performed under the specific conditions and applied current. The aluminium of the anode or aluminium alloy is oxidized, and a thin layer of aluminium oxide is formed on the surface, the aluminium anodizing thickness is 5-30 micrometers, and the hard anodized film can reach 25-150 micrometers. Anodized aluminum or aluminium alloy improves its hardness and abrasion resistance, up to 250-500 kg / mm², good heat resistance, melting point of hard anodized film as high as 2320K, excellent insulation and impact resistance

The breakdown voltage is as high as 2000V, which enhances the corrosion resistance and does not corrode for thousands of hours in the salt spray of ω = 0.03NaCl. There are a large number of micropores in the thin layer of the oxide film, which can absorb various lubricants, which is suitable for manufacturing engine cylinders or other wear-resistant parts. The micropores of the film have strong adsorption ability and can be coloured into various beautiful colours. Non-ferrous metals or their alloys (such as aluminium, magnesium and their alloys) can be anodized. This method is widely used in mechanical parts, aircraft and automobile parts, precision instruments and radio equipment, daily necessities and architectural decoration.

aluminium anodizing process

Aluminium Anodizing Process

Can we anodize die cast aluminum?

the answer is Yes, The surface of aluminium alloy die casting is easy have defects such as welding mark, cold crack, and porosity. we need to do some extra surface treatment to cover it, before we run anodizing on it directly . but part aluminium extrusion parts we can run anodizing directly, and the electroplating is more suitable to zinc aluminium alloy or zinc alloy die casting.

Polishing / Sandblasting / Brushing → Degreasing → Masking → Anodizing 1 → Anodizing 2 → Sealing → Drying

anodized coating thickness

Aluminium Anodizing Layer

Die Casting Aluminium Anodizing Solution

Die castings can complete the difficult structure, edges and corners, which is CNC parts hard to achieve. the keypoint of oxidation quality is based on die casting parts quality, A small change and detailed process control determine the quality of the anode. Engaged in the oxidation of die castings
Manufacturers must scientifically control the runner technology, die casting process and post-processing of parts.With this series of strict control Process to ensure smooth production of oxidation quality

The design of the mold runner and gate

And the control of the mold temperature; due to the characteristics higher aluminum content in the raw material, poor fluidity and high working temperature,
The mold runners and gates are designed based on the short range design; the water transport channel should use a mold temperature machine to ensure Uniform of mold temperature. overcome the flow marks defect.

Use of raw materials to avoid pollution factors

Choose raw materials with low impurity content; eliminate silicon, copper, iron and zinc elements during production,high-quality graphite crucibles must be used separately, and cannot be mixed with other raw materials for production

Process control in the die-casting process

Reducing water ripples; using professional release agents during die-casting, scientific spraying, reducing cavity Residual water drops, avoiding water marks on the die casting, controlling the pressure and speed of the die casting, reducing local filling overpressure, and easy to stick die.

Pre-roughcast processing

After machining, according to the needs of the product, manually polish or grind to remove burrs and flash.

Selection of anodizing companies

Because the bottom layer of the die castings contains different degrees of shrinkage and dirt, the pre-treatment(Cleaning or Degreasing) of Anodizing must be handled, to ensure the quality of aluminium alloy die casting anodizing,The General post-oxidation process cannot meet the oxidation process of die castings.Before mass production, it should be tested and audited to verify suitability.