The structure and application of anodic oxidation
anodic oxidation film structure of the anodic oxidation film is composed of two layers, the outer layer called the porous layer, thicker, porous, low resistance. The inner layer is called blocking layer ( Also called active layer) , thin, high density, resistance. Outer layer is in the dielectric properties of porous density on the inner layer of growing up. Overall, anodic oxide film is hexagon cylinder array, each cylinder to a full solution of radial holes, shaped like a honeycomb structure, the thickness of the wall of hole twice the diameter of the pore. ( 1) Barrier layer barrier layer is composed of the anhydrous AI2O3, thin and compact, has high hardness and prevent the current role. ( 2) Porous outer oxide film of the outer layer is mainly composed of amorphous AI2O3 and a small amount of r - AI2O3。 H2O also contain electrolyte anions. Oxide film in the aperture between 100 nm to 200 nm, thickness of oxide film about 10 microns, porosity 20%, hole spacing between 300 ~ 500 nm. Oxide film section show that oxidation film hole is basically a tubular structure, oxide film dissolve membrane reaction is basically in the bottom of the hole. While sulfuric acid dc anode oxidation membrane pore size is about 20 nm, if is 12 micron oxide film, that's how deep fine tubular structure! Assume that this is a 1 m diameter of the well, the well depth so it will have 600 m deep. Most of the good qualities of oxide film, such as corrosion resistance, abrasion resistance, insulation performance, such as adsorption, aluminium alloy profile is determined by the thickness and porosity of porous outer, but both are closely associated with anodic oxidation conditions, therefore can be get by changing anodization conditions meet the requirements of the use of different membrane layer. Film thickness anodic oxidation products is a major performance a pointer, the size of its value directly affects the coating corrosion resistance, abrasion resistance, insulation and chemical coloring ability. In the process of conventional anodic oxidation, thickening of membrane layer increased with the increase of time. After spreading to the largest thickness, as the extension of processing time and thinning, some alloys such as AI - Mg、AI- Mg- Zinc alloy was especially obvious. Therefore, oxidation time general control within the ability of the biggest film thickness of time. 2) Anodic oxidation film properties and application of anodic oxide film with high hardness and wear resistance, strong adhesive ability, strong adsorption ability, good corrosion resistance and electrical insulation and high resistance to thermal insulation. Due to the specific performance, in various aspects have been widely used. Main use: ( 1) Improve parts of corrosion resistance, corrosion resistance and climate. （ 2) Coloring, oxide generated by the transparent membrane, can produce all kinds of color film. （ 3) As a capacitor dielectric film. （ 4) And the adhesion strength of the organic coating. As a coating layer. （ 5) As the bottom layer of plating, enamel. （ 6) Is developing other USES, solar panels, ultra hard film, dry lubricating film, catalytic membrane, nanowires, sedimentary magnetic alloys for memory in porous membrane element.