Five Characteristics of Anodic Oxide Film on Electric Heating Tubes

Five Characteristics of Anodic Oxide Film on Electric Heating Tubes

1. Hardness of anodized film

The hardness of aluminum and aluminum alloy anodizing films is related to the alloy composition, anodizing method, and process specifications. The hardness of the oxide film near the base metal is higher than that of the surface layer oxide film. Under the same anodizing conditions, the hardness of pure aluminum oxide film is higher than that of aluminum alloy oxide film.

2. Insulation of Anodic Oxide Film

Anodic oxide films are generally non-conductive and have good insulation properties. When the temperature is 5-25 ℃, the resistance is 03 Ω/㎡, and when the temperature is 250 ℃, the resistance is 07 Ω/㎡. Compared with other insulation materials, using oxide film as insulation material has its unique characteristics, such as thin oxide film, high temperature resistance, and resistance to the erosion of water vapor and other corrosive gases. The disadvantages are low elasticity, high moisture absorption, and low voltage resistance.

3. Chemical stability of anodic oxide film

The anodic oxide film has high chemical stability and high corrosion resistance. The oxide film obtained by ordinary oxidation method is mainly used for the surface protection layer of aluminum and aluminum alloy parts. The protective ability of an oxide film depends on its thickness, degree of porosity, and the alloy composition of the base metal. The corrosion resistance of oxide films on pure aluminum or coated with pure aluminum materials is superior to that of aluminum alloys. Because aluminum alloys contain metals that do not form oxide films, their corrosion resistance is reduced.

4. Porosity of Anodic Oxide Film

Anodic oxide films are porous and have high adsorption capacity, which can adsorb various dyes, salts, lubricants, paraffins, dry oils, resins, etc. The oxidized parts can be dyed into various colors for surface decoration, such as commonly used pen caps, cigarette boxes, various aluminum plates, etc. If the oxide film adsorbs photosensitive agents, it can be made into a pattern and a dial for the instrument. The purpose of filling lubricant with oxide film is to increase wear resistance and reduce friction coefficient. Filling the pores of the oxide film with paraffin, dry oil, and resin can improve corrosion resistance and insulation.

5. Adhesion of anodic oxide film

The oxide film is directly generated from the base metal and is firmly bonded to the base metal, making it difficult to peel off from the base metal using mechanical methods. After oxidation, the sheet metal parts are bent until they break, and the oxide film remains on the metal. From this point of view, the bonding force is much higher than that of coating. However, due to the brittleness of the oxide film, parts treated with oxidation undergo significant impact loads and bending deformation, and the oxide film first cracks in a network, reducing the ductility and surface protection ability of the base metal. Therefore, oxidized parts cannot withstand significant pressure and deformation.