Recently, some customers called to inquire about hard oxidation related issues. Today, PTJ used their leisure time to talk to friends carefully.
Hard oxidation of aluminum alloy has its unique advantages, and it is really different from ordinary oxidation:
First, the advantages of hard oxidation of aluminum alloy:
1. The surface hardness of aluminum alloy after hard oxidation is up to about HV500.
2. The thickness of the oxide film is 25-250um.
3. Strong adhesion. According to the oxidation characteristics generated by hard oxidation, 50% of the oxide film penetrates into the aluminum alloy, and 50% adheres to the aluminum alloy surface (bidirectional growth).
4. Good insulation: breakdown voltage can reach 2000V (perfect sealing).
5. Good wear resistance: For aluminum alloys with a copper content of less than 2%, the maximum wear index is 3.5 mg / 1000 revolutions. The wear index of all other alloys should not exceed 1.5 mg / 1000 revolutions.
6. Non-toxic: The oxide film and the electrochemical process used to produce the anodized film are harmless to the human body. Therefore, in order to reduce the weight of the products, the convenience of machining, and the requirements of environmental protection and low toxicity in many industries, some parts of some products currently use aluminum alloy hard oxidation instead of stainless steel, electroplating hard chromium and other processes.
Second, the difference between hard anodizing and ordinary anodizing:
50% of the hard oxidized oxide film penetrates into the aluminum alloy and 50% adheres to the surface of the aluminum alloy. Therefore, the external size of the product becomes larger and the internal pores become smaller after hard oxidation.
1. Differences in operating conditions:
 The temperature is different: ordinary oxidation is about 18-22 ° C, and those with additives can reach 30 ° C. If the temperature is too high, powder or cracks are likely to occur; hard oxidation is generally below 5 ° C, and the lower the temperature, the higher the hardness. .
 Concentration difference: general oxidation is generally about 20%; hard oxidation is generally 15% or lower.
 Current / voltage difference: ordinary oxidation current density is generally: 1-1.5A / dm2; and hard oxidation: 1.5-5A / dm2; ordinary oxidation voltage is ≤18V, and hard oxidation sometimes reaches 120V.
2. Differences in film properties:
 Film thickness: the thickness of ordinary oxide film is relatively thin; the thickness of hard oxide film is generally greater than 15μm, which is too low to meet the requirement of hardness ≥300HV.
 Surface state: The ordinary oxidized surface is smoother, while the hard oxidized surface is rougher (microscopic, related to the substrate surface roughness).
 Porosity is different: ordinary oxidation porosity is high; hard oxidation porosity is low.
 Ordinary oxidation is basically a transparent film; hard oxidation is an opaque film due to its thickness.
 Different application occasions: ordinary oxidation is suitable for decoration; hard oxidation is mainly for function, and is generally used for wear-resistant and electric-resistant occasions. These are more performance comparisons we usually use, and there are many other differences.