What is anodizing?

- Mar 25, 2019-

What is anodizing?

     The so-called anodic oxidation of aluminum is an electrolytic oxidation process in which the surfaces of aluminum and aluminum alloys are usually converted into an oxide film which has protective, decorative and some other functional properties. The anodization of aluminum from this definition includes only the part of the process of forming an anodized film.

    What is the difference between anodizing and conductive oxidation?

     A metal or alloy article is used as an anode, and an oxide film is formed on the surface by electrolysis. Metal oxide films alter surface conditions and properties such as surface coloration, improved corrosion resistance, enhanced wear resistance and hardness, and protection of metal surfaces. For example, aluminum anodizing, aluminum and its alloys are placed in the corresponding electrolyte (such as sulfuric acid, chromic acid, oxalic acid, etc.) as an anode, and electrolysis is carried out under specific conditions and an applied current. The aluminum of the anode or its alloy is oxidized, and a thin layer of aluminum oxide is formed on the surface, and the thickness thereof is 5 to 30 μm, and the hard anodized film is 25 to 150 μm. Aluminized aluminum or its alloy improves its hardness and wear resistance up to 250-500 kg/mm 2 , good heat resistance, hard anodized film melting point up to 2320K, excellent insulation, and resistance to attack The wearing voltage is up to 2000V, which enhances the corrosion resistance and does not corrode in thousands of hours in the salt fog of ω=0.03NaCl. The oxide film has a large number of micropores in the thin layer, which can adsorb various lubricants, and is suitable for manufacturing engine cylinders or other wear-resistant parts; the membrane microporous adsorption ability can be colored into various beautiful and beautiful colors.

What is the difference between anodizing and conductive oxidation?

    1) Anodizing is carried out under high voltage, it is an electrochemical reaction process; conductive oxidation (also called chemical oxidation) does not require electricity, but only needs to be soaked in the syrup, it is a a pure chemical reaction.

    2) Anodizing takes a long time, often several tens of minutes, while conductive oxidation requires only a few tens of seconds.

    3) The film formed by anodization has a few micrometers to several tens of micrometers and is hard and wear resistant, while the film formed by conductive oxidation is only 0.01-0.15 micrometers. The wear resistance is not very good, but it is both electrically conductive and resistant to atmospheric corrosion, which is its advantage.

    4) The oxide film is inherently non-conductive, but since the film formed by conductive oxidation is really thin, it is electrically conductive.

 The role of anodizing:

    1. Protective;

    2. Decorative;

    3. Insulation;

    4. Improve the bonding with the organic coating;

    5. Improve the bonding force with the inorganic coating layer;

    6. Other features in development.

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