Anodizing is a process in which an oxide film is formed on the surface of aluminum by electrolytic oxidation. In this process, the aluminum plate coil is used as the anode, placed in the electrolytic cell, and sulfuric acid, oxalic acid, etc. as the electrolyte will be used as the electrolyte. After the current is applied, the aluminum surface begins to oxidize and form an aluminum oxide film. The colorless and porous nature of the anodized film is used to achieve the purpose of dyeing and protecting the aluminum substrate.
Process flow of anodizing
The anodizing process is mainly from degreasing → etching → neutralization → anodizing → coloring → sealing.
Good corrosion resistance and weather resistance: aluminum oxide film has strong corrosion resistance, can form a protective layer on the surface of aluminum, prevent aluminum from contacting with the external environment, use for a long time without discoloration, no corrosion, no oxidation, no rust , thereby prolonging the service life of the product.
High hardness: Aluminum oxide film has a fairly high hardness, ranging from a few microns to dozens of microns, which makes the aluminum oxide film have excellent performance in some fields such as decoration and electronic product casing.
Color and appearance: The color and appearance of aluminum oxide film can be adjusted by controlling process parameters and dyeing methods. This makes the anodized aluminum plate not only retains the metal texture, but also can be customized in a variety of colors to meet different aesthetic and design needs.
Strong applicability: Anodizing is suitable for various series and grades of aluminum alloys; it is also suitable for aluminum coils with different surface treatments (Mill, Bright, Polished, Hairline, Stucco, Embossed, Etching, etc.); the product has a wide range of uses and is suitable for Metal aluminum ceiling, curtain wall aluminum panel, aluminum-plastic panel, fireproof board, honeycomb aluminum panel, aluminum veneer, electrical panel, cabinet panel, furniture panel, etc.
Different grades of wrought aluminum alloys have different compositions, heat treatment processes and corresponding processing shapes, so they have different anodizing characteristics. Not all aluminum alloy sheets are suitable for anodizing. The aluminum plates coil usually used for anodizing mainly include 1xxx series, 3xxx series, 5xxx series and 6xxx series aluminum alloy plates.
1xxx series aluminum plate: pure aluminum alloy, generally not used for hard anodizing. But has very good properties in bright anodizing and protective anodizing. Represents alloys 1050, 1060, 1070, 1100, commonly used in decoration, signs, electronic product casings, etc.
3xxx series aluminum plate: it will not reduce the corrosion resistance of the anodized film, but the anodized film will appear gray or grayish brown. Represents alloys 3003, 3004, 3005, 3105, suitable for some applications requiring corrosion resistance, such as beverage cans, chemical equipment, etc.
5xxx series marine grade aluminum plate: It is a widely used aluminum alloy with good corrosion resistance and good weldability. Commonly used alloys are 5005, 5052, 5083, 5086, 5251, etc., which are usually used in applications in some external environments, such as building materials, auto parts, etc., and are also used in shipbuilding, aerospace, etc. that require high strength and corrosion resistance field.
6xxx series aluminum plate: Typical alloys are 6061 and 6063 anodized aluminum plates, which are suitable for bright anodizing and have good surface treatment properties, suitable for applications requiring exquisite appearance such as decoration, construction, and electronic product casings.
7xxx series aluminum plate: represents alloy 7075, which is a high-strength aluminum alloy and is usually used in applications requiring extremely high strength, such as aerospace, high-performance mechanical parts, etc.
The thickness of the oxide layer on the surface of the anodized aluminum coil is 3-20 μm, and the application of products with different thicknesses of the oxide layer is also different: