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Type 2 Sulfuric
Acid Anodize

What is Type 2 Sulfuric Acid Anodize?

Type 2 Anodizing, also called Sulfuric Acid Anodize, is the most common method for anodizing. The process changes the surface of an aluminum substrate material creating a protective aluminum oxide layer.

It is particularly well-suited for applications where hardness and resistance to abrasion is desired.

Sulfuric Acid Anodize also is used to improve surface corrosion and protection under severe service conditions, or as a base for paint systems. The porous nature of sulfuric acid films prior to sealing particularly is used to advantage in the production of colored surface finishes on aluminum and its alloys.



  • Type 2

    • The conventional sulfuric acid anodizing treatment

  • Type 2B

    • A non-chromate alternative to Type 1 and Type 1B coatings, where corrosion resistance, paint adhesion, and fatigue resistance are all required.

    • Provides better corrosion resistance than Chem Film and provides adequate base for organic paint finishes

Properties & Benefits

  • Coating Thickness: ~ .0001 to .001 inches, depending on specs/process or alloy

    • Note: Anodize Coating Thickness is surface penetration plus surface build-up

  • Substrates: A wide variety of aluminum alloys

    • Including 1100, 2000, 3000, 5000, 6000, and 7000 series alloys

    • Note: Please click through to the individual spec pages (linked below) to see the standard coating thickness for specific alloys
  • Benefits:

    • Corrosion protection

    • Abrasion resistance

    • Increased hardness

    • Improved Thermal or electrical insulation

    • Increased lubricity 

    • A much thinner coating compared to paints or powder-coat finishes

    • The dimensional build-up often can be ignored for machined parts

  • Compared to Type 1 Chromic Acid Anodizing

    • More aluminum alloys can be finished compared to other processes

    • Clearer finish permits dying with a greater variety of colors

    • Less expensive than other Anodize processes with respect to the chemicals used,
      less heating & power consumption

    • Shorter plating time to reach specified thickness

Applications / Industries

  • Military weapons

  • Optical components

  • Medical components

  • Mechanical hardware

  • Decorative applications

  • Computer & electronic enclosures

  • Hydraulic valve bodies

Specs & Certifications

  • AMS-A-8625 --- NADCAP Approved, ROHS Compliant
  • MIL-A-8625 --- NADCAP Approved, ROHS Compliant
  • MIL-PRF-8625

Contact Us

If you have a unique part, specialized needs or simply want to work with the best, please reach out and let us know how we can help you achieve the results you need.

If you need a finishing partner who will listen carefully and then Make it Happen for You, call AOTCO at 1 888 275 0880

Since 1975 AOTCO Metal Finishing LLC has delivered outstanding results for clients with the toughest requirements for metal finishing.

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