Many people are not clear about what specific process "aluminum oxidation" refers to. Here is a brief introduction for everyone:

Aluminum oxidation: the process of using aluminum or aluminum alloy products as the anode, placing them in an electrolyte solution for electrical treatment, and using electrolysis to form an aluminum oxide film on their surface is called anodic oxidation treatment of aluminum and aluminum alloys. After anodic oxidation treatment, an oxide film from several microns to several hundred microns can be formed on the aluminum surface. Compared with the natural oxide film of aluminum alloys, its corrosion resistance, wear resistance, and decorative properties are significantly improved and enhanced.

The principle of aluminum anodic oxidation is essentially the principle of water electrolysis. When current passes through, the following reactions occur: at the cathode, H2 is released according to the reaction 2H+ + 2e → H2; at the anode, 4OH- - 4e → 2H2O + O2. The oxygen released is not only molecular oxygen (O2) but also atomic oxygen (O) and ionic oxygen (O2-), and it is usually expressed as molecular oxygen in the reaction. The aluminum acting as the anode is oxidized by the oxygen released on it to form an anhydrous Al2O3 film: 2Al + 3[O] → Al2O3 + 1675.7 kJ. It should be noted that not all of the generated oxygen reacts with the aluminum; part of it is released in gaseous form.

Types of anodic oxidation: anodic oxidation has long been widely used in industry. There are many methods under different names, which can be summarized into the following categories:

Classified by current type: direct current anodic oxidation, alternating current anodic oxidation, and pulse current anodic oxidation, which can shorten the production time required to reach a given thickness while producing a thick, uniform, and dense film with significantly improved corrosion resistance;

Classified by electrolyte: sulfuric acid, oxalic acid, chromic acid, mixed acid, and natural-color anodic oxidation using organic sulfonic acid solutions;

Classified by film properties: ordinary films, hard films (thick films), porcelain films, bright decorative layers, and barrier layers with semiconductor effects;

The direct current sulfuric acid anodic oxidation method is the most widely used because it is suitable for the anodic oxidation treatment of aluminum and most aluminum alloys; the film is thicker, hard, and wear-resistant, and better corrosion resistance can be obtained after sealing; the film is colorless and transparent with strong adsorption capacity and is easy to color; the treatment voltage is low and power consumption is small;

The process does not require changing the voltage cycle, which is conducive to continuous production and automated operation; sulfuric acid is less harmful to the human body than chromic acid, is widely available, and is low in price.

Over the past decade, the construction industry in China has gradually adopted aluminum doors and windows and other decorative aluminum materials, and their surface treatment production lines all use this method.