Surface treatment technology of aluminum alloy

Aluminum Alloy materials are increasingly widely used in the automotive industry. They not only conform to the current trends of automotive electrification, lightweighting and energy conservation, but also have the advantages of low forming temperature, good processing performance, excellent forgeability and plasticity. At the same time, they are easy to recycle and reuse, and have high environmental protection advantages and cost-effectiveness. Its common surface treatment techniques include passivation, anodizing, organic coating, etc。

1.Passivation

Passivation of aluminum alloy is a process where the substrate is immersed in a passivation solution to undergo a chemical reaction, forming a dense, continuous, firm and uniform oxide film on the surface, thereby enhancing the corrosion resistance of the substrate. The commonly used passivation processes mainly include several steps such as degreasing, ultrasonic cleaning, activation and passivation. Passivation treatment does not require external power supply or special fixtures, is not restricted by size, has high productivity and low processing costs. It is an ideal choice for the automotive industry that needs to handle a large number of complex structures and components. The main influencing factors affecting passivation performance are:

1.The composition of the passivator.

 At present, the passivators used for aluminum alloy passivation are mainly divided into chromate passivation and chromium-free passivation. The anti-corrosion performance is usually as follows: hexavalent chromium passivation > trivalent chromium passivation > chromium-free passivation. Under normal circumstances, the higher the concentration of chromium oxide, the greater the thickness of the passivation layer, and the better the anti-corrosion and wear resistance performance. Although hexavalent chromium passivation has the best quality, due to environmental protection requirements, trivalent chromium passivation and chromium-free passivation are mainly used now. Chromium-free passivation includes zirconium-titanium treatment, silane treatment, cobalt salt passivation, permanganate passivation, rare earth passivation, etc. Its anti-corrosion performance is also much inferior to that of chromate passivation. Although many regions require the use of chromium-free passivation for environmental protection reasons, at present, chromium-free passivation cannot completely replace chromate passivation. This needs to be taken into consideration in actual design and production.

2.Passivation process.

Process parameters such as temperature and pH value, as well as activation processes, ash removal processes, and secondary passivation, all have an impact on the anti-corrosion performance of the product.

2.Anodized

Anodized is an electrolytic oxidation process. When an aluminum alloy is used as the anode and placed in an electrolyte containing acid or salt and a direct current power supply is applied, an electrochemical reaction occurs to form aluminum anodized, and a layer of oxide film is transformed on the surface. The thickness, density and hardness of the oxide film can all be adjusted according to current density, time, electrolyte type, concentration, etc. This anodized film is firmly bonded to the base metal and has excellent corrosion resistance, decorative properties, wear resistance and electrical insulation, which can be applied in a variety of fields.

Changyin'scontinuously explores the strength potential of Aluminum Materials, enabling this seemingly ordinary metal to play a crucial role in various fields that require high-strength support, and writing a "strength legend" of aluminum materials.