Hard Anodizing

Hard coat or hard anodizing (Type III) is similar to standard anodizing, (Type II) in as much as it also creates a film of aluminum oxide on the part. It is produced at colder temperatures and provides a surface that is harder, smoother, and more wear and corrosion resistant than standard anodizing.Hardcoat finishes are typically darker in appearance than standard anodizing depending on the coating, thickness and alloy. A variety of colors are available on thinner coatings. Heavier coatings can be dyed black and some darker shades of color. Arnold’s Metal Finishing Type III Anodizing Plating Capabilities:

  • Typical Formed Thickness is 0.0010 to 0.0040 in.
  • Available with PTFE (Teflon)
  • Rack Anodizing
  • Available Masking for Selective Surface Anodizing
  • Salt Spray Corrosion Test (minimum 336 hours of salt spray resistence)
  • Thickness Analysis, Coating Weight
  • Taber Abrasion Test
  • Dielectric Testing

Applicable Specifications:

MIL-A-8625F Type III MIL-STD-186D (207) MIL-STD-171D(7.5.1 & 7.5.2)
MIL-C-60536 MIL-STD-193K MIL-F-14072C (E514)
AMS B117 AMS 2468 & 2469 ASTM B580-79 (Type A)


  1. Color will vary from light tan to black depending on alloy and thickness.
  2. Coating PENETRATES base metal as much as builds up on the surface.
  3. The term THICKNESS Includes both, the buildup and penetration.
  4. Provides very hard ceramic type coating.
  5. Abrasion resistance will vary with alloy and thickness of coating.
  6. Good dielectric properties.
  7. Corrosion resistance is good, but recommend seal hard anodize In 5% dichromate solution where increased corrosion resistance is required. Where extreme abrasion resistance is required do not seal as some softening is encountered.

Typical Applications of Hard Anodizing are: Machinery, excellent abrasion resistance for high-speed machine  arts; Electronics, provides uniform emissive and a high dielectric; Marine, long-lasting corrosion resistance in salt-water; Oil and Petrochemical, excellent corrosion and wear resistance; Aviation and Space, durability and longevity; Ordnance, corrosion protection, and abrasion and wear resistance; Cookware, corrosion protection and non-stick properties.

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