The principle of aluminum anodization is essentially the principle of water electrolysis. When the current passes, the following reaction will take place:
In the cathode, according to the following reaction release H2: 2H + + 2e → H2
On the anode, 4OH - 4e → 2H2O + O2, the oxygen is not only molecular oxygen (O2), but also atomic oxygen (O) and ionized oxygen (O-2) .
Aluminum as the anode is oxidized by the oxygen precipitated thereon to form an anhydrous Al2O3 film: 2AI + 3 [O] = AI2O3 + 1675.7 KJ It is to be noted that not all of the generated oxygen acts on aluminum and part of it is precipitated as a gaseous form .
Anodizing types Anodic oxidation has long been widely used in industry. Crowded with different names of many ways, summed up the following categories:
Divided according to the current type: DC anodic oxidation, AC anodization, and can shorten the production time required to reach the thickness of the film thick and uniform dense, and significantly improved corrosion resistance of the pulse current anodic oxidation.
Divided by the electrolyte: sulfuric acid, oxalic acid, chromic acid, mixed acid and natural coloring with organic sulfonic acid solution anodizing.
Divided by the nature of the film: ordinary film, hard film (thick film), porcelain film, light modification layer, the role of semiconductor barriers such as anodic oxidation.
DC Sulfuric acid anodic oxidation method is most commonly used because of its anodization suitable for aluminum and most aluminum alloys; thicker film, hard and wear-resistant, better corrosion resistance after sealing; The film is colorless and transparent, easy to color strong adsorption capacity; lower processing voltage, low power consumption; process does not have to change the voltage cycle is conducive to continuous production and operation of automation; , Low price and other advantages.