Hardcoat and Clear Aluminum Anodizing Example

Hardcoat Aluminum Anodizing (Nadcap Accredited)

Hardcoat Anodizing, often called "Type III anodizing" as denoted by the MIL-A-8625 specification, is an electrochemical process that creates a controlled oxide film on the surface of aluminum. Hardcoat Anodizing utilizes sulfuric acid, low bath temperatures, and high voltage to produce a very high surface hardness (60-70 Rockwell C). Hardcoat Anodizing is generally used for applications that need a corrosion, abrasion, and wear resistant coating. The appearance of the coating ranges from light to dark gray, depending on the alloy makeup of the aluminum substrate, and it can also be dyed black. Parts can be processed with multiple finishes, such as Hard Coat/Chem Film or Hard Coat/Electroless Nickel Plating.

Note to engineers: the oxide film created by the anodizing process penetrates into the base material at a rate nearly equivalent to the rate at which it grows on the surface. For this reason, a total film thickness of 0.002" will cause a dimensional change of 0.001". For the same reason, hardcoat anodizing lowers the fatigue strength of aluminum. In stress applications chromic acid anodizing (MIL-A-8625 Type I) or thin film sulfuric acid anodizing (MIL-A-8625 Type IIB)  should be used instead of hardcoat anodizing.

Chem Processing performs anodizing operations on an automated processing line (in service 06/2022). Anodized films are generated by software-controlled methods for a precise finish and exact records.

For a discussion of hardcoat anodizing thickness, see our "Planning for Anodizing Buildup" page.


    Properties of Hardcoat Anodizing:

    • Compatible with adhesives
    • Excellent lubricity (enhanced by PTFE impregnation)
    • Resistant to marine and atmospheric corrosion
    • High operating temperatures
    • Electrically resistant
    • Galvanic neutrality (prevents galvanic corrosion from interaction between dissimilar metals)

    Chem Processing Inc. Hardcoat Anodizing Capabilities:

    • Thickness ranges: 0.0001" to 0.0030"  NOTE: anodizing thickness constitutes 50% build, 50% penetration into the substrate, which must be accounted for when calculating pre-anodize machining tolerances
    • Available with PTFE (Teflon®) impregnation for enhanced tribological properties
    • Rack and bulk processing
    • Precision masking for selective anodizing
    • In-house salt spray testing ber ASTM B 117
    • In-house coating weight analysis
    • Taber abrasion testing
    • Post anodize seals available for increased corrosion resistance but may reduce surface hardness
    • Type I and Type II as masking
    • Nadcap accredited process

      Applicable Anodizing Specifications:

    • MIL-A-8625F Type III
    • ASTM B580-79 (Type A)
    • CP-1000 (UTAS)
    • MIL-STD-171
    • AMS 2468 & 2469
    • SP-222 (Woodward)
    • 580-0008 (Rockwell Collins)

    Typical Hardcoat Anodizing Applications:

    • Aerospace/Astrospace/Aviation: wear resistance, dry lubrication, longevity and electrical insulation
    • Firearms: corrosion and wear resistance on AR-15 upper receivers, hand guards and similar components
    • Machinery: abrasion resistance for high-speed machine parts
    • Electronics: uniform emissivity and a high dielectric
    • Oil and Petrochemical: corrosion protection and wear resistance.
    • Ordnance: corrosion protection, abrasion resistance and wear resistance
    • Cookware: corrosion protection and non-stick properties
    • Molds and Dies: improved release properties and abrasion resistance
    • Sporting Goods: improved durability and performance

    Chem Processing Inc. offers hardcoat anodizing services to Illinois, Wisconsin, Iowa, the Midwest and beyond. CPI is strategically located by highway routes to Chicago, Milwaukee, Madison, St. Louis, and Minneapolis. The CPI facility is minutes from Rockford Chicago International Airport, a major Midwestern air freight hub, enabling efficient door-to-door delivery across the United States or across the globe.