The difference between hard anodizing and ordinary anodizing: 50% of the oxide film of hard oxidation penetrates into the interior of the aluminum alloy and 50% adheres to the surface of the aluminum alloy. Therefore, after hard oxidation, the external size of the product becomes larger and the inner pores become smaller. Therefore, in order to reduce the weight of products, facilitate machining, and be environmentally friendly and low-toxic, many industries currently use aluminum alloy hard oxidation to replace stainless steel, electroplating hard chromium and other processes for some parts of some products.

Hard oxidation
1. Differences in operating conditions
1. Different temperatures: Ordinary oxidation is around 18-22°C, and with additives it can reach 30°C. If the temperature is too high, powder or cracks may easily appear; hard oxidation is generally below 5°C. Relatively speaking, the lower the temperature, the higher the hardness.
2. Concentration difference: ordinary oxidation is generally about 20%; hard oxidation is generally 15% or less
3. Current/voltage difference: The current density of ordinary oxidation is generally: 1-1.5A/dm2; and hard oxidation: 1.5-5A/dm2; ordinary oxidation voltage is ≤18V, and hard oxidation is sometimes as high as 120V
2. Differences in film performance
1. Film thickness: The thickness of ordinary oxidation film is relatively thin; the thickness of hard oxidation film is generally >15μm, which is too low to meet the requirement of hardness ≥300HV
2. Surface condition: The ordinary oxidized surface is smooth, while the hard anodized surface is rough (microscopic, related to the surface roughness of the substrate)
3. Different porosity: ordinary oxidized porosity is high; while hard oxidized porosity is low
4. Ordinary oxidation is basically a transparent film; hard oxidation is an opaque film due to the thickness of the film.
5. Applicable occasions are different: ordinary oxidation is mainly suitable for decoration; while hard oxidation is mainly functional and is generally used in wear-resistant and electricity-resistant occasions.
The above are comparisons of performance that we usually use. There are many other differences between hard anodizing and ordinary anodizing.