the electrochemical oxidation
of a metal or alloy. The process by which aluminum and its alloys form an oxide film on aluminum products
(anodes) under the action of an applied current under the corresponding electrolyte and specific technological conditions. Anodizing, if not specified, isusually sulfuric acid anodizing.
In order to overcome the surface hardness, wear resistance and other defects of aluminum alloy, expand the application range and extend the service life, surface treatment technology has become an indispensable link in the use of aluminum alloy, and
anodic oxidation technology is currently the most widely used and most successful. Electrochemical oxidation of metals or alloys
Usually refers to Sulfuric acid anodizing.
Anodizing of aluminum is an electrolytic oxidation method. In which the surface of aluminum and aluminum alloys is usually transformed into an oxidation film, which has protective, decorative and other functional properties. Anodizing of aluminum from this definition includes only the process of forming anodized films.
A thin oxide film is formed on the surface of a metal or alloy as an anode by electrolysis. Metal oxide films change the surface state and properties, such as surface coloring, improve corrosion resistance, enhance wear resistance and hardness, and protect the metal surface. For example, aluminum and its alloys are anodized by placing them in corresponding electrolytes (such as sulfuric acid, chromic acid, oxalic acid, etc. as anodes to conduct electrolysis under specific conditions and applied current. The anodic aluminum or its alloy is oxidized to form a thin layer of alumina on the surface with a thickness of 5 ~ 30 microns and a hard anodic film of 25 ~ 150 microns. Anodized aluminum or its alloy, improve its hardness and wear resistance, up to 250 ~ 500 kg/square mm, good heat resistance, hard anodized film melting point up to 2320K, excellent insulation, breakdown voltage up to 2000V, enhance the anti-corrosion performance, in the ohm =0.03NaCl salt spray for thousands of hours without corrosion. The thin layer of oxide film has a large number of micro holes, can adsorb a variety of lubricants, suitable for making engine cylinders or other wear-resistant parts;
The membrane pores have strong adsorption ability and can be colored into various beautiful and gorgeous colors. Nonferrous metals or their alloys (such as aluminum, magnesium and their alloys) can be anodized, which is widely used in mechanical parts, aircraft and automobile parts, precision instruments and radio equipment, daily necessities and architectural decoration.
Generally speaking, the anode is made of aluminum or aluminum alloy as the anode, and the cathode is made of lead plate. The aluminum and lead plate are put together in an aqueous solution, which contains sulfuric acid, oxalic acid, chromic acid, etc., for electrolysis, so as to form an oxidation film on the surface of the aluminum and lead plate. The most extensive of these acids is anodic oxidation with sulfuric acid.
Other types of
Oxidation caused by anodizing other substances other than metals is also known as "anodizing".
In the real process, the anodization of aluminum alloy is more and more, which can be applied in daily life. Because of the characteristics of this process, the surface of aluminum parts has a hard protective layer, which can be used in the production of kitchen utensils and other daily necessities. However, the anodizing effect of cast aluminum is not good, the surface is not bright, and can only be black. Aluminum profiles are better.
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