The concept and function of anodising of aluminum

The concept and function of anodising of aluminum

The concept of anodising: the process by which an oxide film is formed on aluminium and its alloys under the action of an applied current in the corresponding electrolyte and under specific process conditions (anode). If not specified, anodising usually refers to sulphuric acid anodising

1. The function of anodising:

　　☆Protective

　　☆Decorative

　　☆Insulation

　　☆Improves adhesion to organic layers.

　　☆Improves adhesion to inorganic coverings

　　☆Other functions in development

　　2. Chemical conversion film treatment of aluminium alloys (chemical oxidation, passivation, chromatisation)

　　★ Chemical conversion film of aluminium alloys is obtained by chemical oxidation, which can be referred to the US military standard MIL-C-5541.

　　★Why is chemical conversion film treatment of aluminium alloy necessary?

　　☆ To strengthen the rust resistance of aluminium alloy.

　　☆ It can play the role of stabilizing the contact electric negative. (Once a customer's product required conductive oxidation, the purpose of which is to play a role in stabilizing contact resistance and conductivity)

　　☆Transformation film is thin (about 0.5~4um), soft, conductive, porous, and has good adsorption ability, and is usually used as a base layer for paints or other coatings.

　　☆Does not change the mechanical properties of the material.

　　☆Simple equipment, easy to operate and cheap.

　　☆Does not affect the size of the workpiece.

　　★Transformation film thickness

　　The chemical conversion film on the surface of aluminium alloy is thin about 0.5~4um, the conversion film is a gel, which is difficult to measure directly, usually only weighing the weight of the workpiece before and after chemical oxidation, or using the surface colour and salt spray test to judge the corrosion resistance of the oxide film.