What’s The Differences Between Hard Anodized And Common Anodized Finish ?

I’d like to say something about the Advantages of Hard Anodized Finish of Aluminum Alloy first.

  1. After hard anodized finish the surface hardness of aluminum alloy can up to HV 500.
  2. Oxide film thickness 25-205um.
  3. Strong adhesion, 50% of the oxide film infiltration into the aluminum alloy, 50% attached to the aluminum alloy surface (two-way growth).
  4. Good insulation: Breakdown voltage up to 2000V.
  5. Good wear resistance: For the aluminum alloy which copper content less than 2%, its maximum wear index is 3.5mg / 1000 turn. For other alloy,  wear index should not exceed 1.5mg / 1000 turn.
  6. Non-toxic: Oxide film and the electrochemical process used to produce the oxide film should be harmless to the human body.

In order to reduce the weight of the product, the convenience of mechanical processing, environmental protection and other requirements, aluminum alloy hard anodized has instead of stainless steel, electroplating hard chrome and other processes in some industries.

What’s the differences between hard anodized and common anodized finish ?

After hard anodized, 50% of the oxide film infiltration into the aluminum alloy, 50% attached to the aluminum alloy surface, so outside sizes will be larger, and inside holes sizes will be smaller.

First: Differences in operating conditions

  1. Temperature is different: common anodized finish temperature is 18-22 ℃, if there are additives temperature can be 30 ℃, it’s easy to arise powder or pattern if temperature is too high; hard anodized finish temperature is generally below 5 ℃, generally speaking lower temperature, the higher of the hardness.
  2. Concentration is different: common anodized concentration is about 20%; hard anodized is about 15% or less.
  3. Current / voltage is different: common anodized current density: 1-1.5A / dm2; hard anodized: 1.5-5A / dm2; common anodized voltage ≤ 18V, hard anodized sometimes up to 120V.

Second: differences in film performance

  1. Film thickness: the thickness of common anodized is thinner; hard anodized film thickness > 15μm.
  2. Surface state: the common anodized surface is smooth, while the hard anodized surface is rough.
  3. Porosity: common anodized porosity is high; and hard anodized porosity is low.
  4. Common anodized film is basically transparent; hard anodized film is opaque because of film thickness.
  5. Applicable to different occasions: common anodized mainly used for decoration; hard anodized finish generally used for wear-resistant, power-resistant occasions.

Above information for reference only. Any comment was welcomed.

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