Passivation and anodizing of aluminum are two different surface treatment methods. They have some differences in technical principles, treatment effects, applicable fields, advantages and disadvantages, etc.

What is aluminum passivation?

Aluminum passivation refers to the chemical reaction between aluminum and aluminum passivation liquid, which will form a uniform, dense, difficult to damage, and very complete passivation protective film on the surface of the aluminum part, thereby preventing external interference. Destructive substances react with the metal surface to extend the corrosion resistance and oxidation resistance of aluminum products, thereby prolonging the rusting time of aluminum materials.


  • Improve salt spray resistance and corrosion resistance by 5-20 times
  • Maintain the color, size, appearance and shape of aluminum product surfaces
  • Facilitates further processing of aluminum products in the later stage, such as electroplating, electrophoresis, anodizing, and spraying
  • Does not affect the basic properties of aluminum products, such as electrical conductivity, thermal conductivity, etc.
  • Environmentally friendly, safe and non-toxic
  • Simple wastewater treatment and low cost of use

Passivation process

  1. Oil removal and degreasing: Immerse the aluminum parts in aluminum cleaning agent and operate at room temperature for 1-3 minutes. After the oil stains on the surface are completely cleaned, take out the aluminum parts and rinse the surface with a cleaner.
  2. Aluminum passivation: Soak the cleaned aluminum parts in the aluminum passivation liquid and operate at room temperature for 1.5 minutes. After the time is up, take out the workpiece immediately and rinse the surface with cleaning.
  3. Pure water: Soak the aluminum parts in pure water (barrel water or filtered water) for 3 minutes.
  4. Dry and package.

What is anodizing?

Anodizing of aluminum is an electrolytic oxidation process in which the surface of aluminum and aluminum alloys is usually transformed into an anodized film that has protective, decorative and other functional properties.

Its purpose is to overcome the defects of aluminum alloy surface hardness, wear resistance and other aspects, expand the scope of application and extend the service life.


  • Good processability: Anodized aluminum has strong decorative properties and is easy to bend and form
  • Good weather resistance: Standard thickness anodized film (3μm) is used indoors. Anodized aluminum plates with thickened anodized film (10μm) can be used outdoors
  • Strong metallic feel: The anodized aluminum plate has high surface hardness, reaching gem level, good scratch resistance, and retains the metallic color of the aluminum plate
  • High fire resistance: pure metal products, no paint on the surface, will not burn at 600 degrees high temperature
  • Strong stain resistance: no fingerprints left, easy to clean
  • Weather resistance: good weather resistance and corrosion resistance

Anodizing process

  1. Remove oil and dirt
  2. Anodizing
  3. Sealing treatment of anodized film
  4. Dyeing treatment
  5. Sealing treatment (optional)

Passivation vs. Anodizing of Aluminum

Five major differences between Passivation vs. Anodizing
Features Passivation Anodizing
Technical principles Chemical methods form an anodized layer on the aluminum surface Anodized film formed by electrolysis
Anodized layer thickness The anodized layer formed by aluminum passivation is generally relatively thin, with a film thickness between 0.5 and 3 μm. The anodized film is about tens of microns, and the thickness can be controlled as needed.
Exterior The surface is brighter, which can protect the beautiful surface of aluminum products and resist oxidation. The anodized layer is denser, the surface is harder, and it can better prevent aluminum corrosion.
advantage The surface will become bright and have better oxidation protection The anodized film has high hardness and high aesthetics
shortcoming The anodized layer is thin and the protective effect is poor The electrolysis process requires high technological requirements and is difficult to produce.
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