The difference between hard anodizing and ordinary anodizing

Yinsheung CNC Machining  2023-08-10 Published in Foshan

Topic

#heatsink fins

#Conducting

#anodizedfilms

#hardanodized

The difference between hard anodizing and ordinary anodizing:

1, The advantages of hard oxidation of aluminum alloy:

1. The surface hardness of aluminum alloy after hard oxidation can reach around HV500.
2. The thickness of the oxide film is 25-250um.
3. Strong adhesion, based on the oxidation characteristics generated by hard oxidation: 50% of the generated oxide film penetrates inside the aluminum alloy, and 50% adheres to the surface of the aluminum alloy (bi-directional growth).
4. Good insulation: The breakdown voltage can reach 2000V (with perfect sealing).
5. Good wear resistance: For aluminum alloys with a copper content not exceeding 2%, the maximum wear index is 3.5mg/1000 revolutions. The wear index of all other alloys should not exceed 1.5mg/1000 revolutions.
6. Non toxic: The oxide film and the electrochemical process used to produce anodic oxide film should be harmless to the human body. Therefore, in order to reduce the weight of products, facilitate mechanical processing, and meet the requirements of environmental protection and low toxicity, many industries currently use aluminum alloy hard oxidation to replace processes such as stainless steel and electroplating hard chromium in some parts of some products.

2, The difference between hard anodizing and ordinary anodizing:

50% of the oxide film of hard anodizing penetrates inside the aluminum alloy, and 50% adheres to the surface of the aluminum alloy. Therefore, after hard anodizing, the external size of the product becomes larger and the internal hole becomes smaller.

（1） Differences in operating conditions:

1. Temperature difference: ordinary oxidation at around 18-22 ℃, with additives up to 30 ℃, and high temperatures are prone to powder formation

End or crack; Hard oxidation is generally below 5 ℃, and relatively speaking, the lower the temperature, the higher the hardness.

2. Concentration difference: Generally around 20% for ordinary oxidation; Hard oxidation is generally at 15% or lower.

3. Current/voltage difference: Normal oxidation current density is generally 1-1.5A/dm2; Hard oxidation: 1.55A/dm2; Ordinary oxidation voltage ≤ 18V, sometimes as high as 120V for hard oxidation.

（2） Differences in film performance:

1. Film thickness: The thickness of the ordinary oxide film is relatively thin; Hard oxidation, general film thickness>15 μ m. Too low to meet the requirement of hardness ≥ 300HV.

2. Surface condition: The ordinary oxidized surface is smoother, while the hard oxidized surface is rougher (micro, related to the surface roughness of the substrate).

3. Different porosity: ordinary oxidation has a higher porosity; However, the porosity of hard oxidation is low.

4. Ordinary oxidation is basically a transparent film; Hard oxidation is an opaque film due to its thickness.

5. Suitable for different occasions: ordinary oxidation is mainly suitable for decoration; Hard oxidation is mainly functional and is generally used in wear-resistant and electric resistant situations.