Aluminum anodic oxidation is put metal as anode in the electrolyte, the metal surface to form dozens to hundreds of microns of oxidation film process, the formation of the layer of oxide film make the metal corrosion prevention, wear-resisting performance. Now in a typical and common anodic oxidation of aluminium and its alloys as an example to illustrate the principle.
Aluminium and aluminium alloy workpiece surface oil removal after pretreatment, as anode, other aluminum plate as cathode, with dilute sulphuric acid (or chromic acid) solution as electrolyte. After electrify, anode reaction is OH - discharge oxygen precipitation, it quickly and anodic aluminum oxide generated, and release a large amount of heat, namely the oxide film in the process of anodic oxidation, near the side of the electrolyte of Al2O3 and from Al203 H20, hardness is lower. Due to the uneven film and acidic electrolyte effect on membrane dissolved, formed a loose hole, porous layer is generated. Reach the surface of the aluminum electrolyte through pine hole, oxide film on aluminum substrate grow continuously.
The oxide film obtained anodic oxidation combined with metal crystal and firm, thus greatly improving the metal and its alloy corrosion resistant ability, and can improve the resistance of the surface and enhance the insulation performance. Can be done after oxidation of aluminium wire motor shaft transformer winding coil. In addition, because the metal aluminium oxide film has porous, adsorption performance is strong, and thus can be infected with all sorts of bright colors, for decoration aluminium. For don't need to stain the surface of the pore, is to be closed, shrink pore, improve the oxidation film corrosion resistance, prevent corrosion caused by corrosive medium into the hole.