Hard Coat Aluminum Anodizing

Arrow Cryogenics Aluminum Hardcoat Anodizing Meets Military Standard Specifications:

  • MIL-A-8625 Type III Class 1 (Non-Dyed) and Class 2 (Dyed)

Arrow Cryogenics offers aluminum hard coat anodizing (Type III) at our state-of-the-art facility in Blaine, Minnesota. We also provide standard aluminum anodizing (Type II) services.

What is Hard Coat Anodizing?

Aluminum Hard Coat Anodizing is similar to standard anodizing in that both are controlled electrochemical processes. The key difference is that hard coat anodizing provides a surface that is more wear resistant and has a smoother and harder surface than standard anodizing.


During the hard coat anodizing process, a uniform aluminum oxide layer is formed on the surface that penetrates into the material. The hard coat anodizing process involves submerging the part(s) in a sulfuric acid bath at approximately 32°F, with a density of 23 to 37 amps, for anywhere from 20 minutes to two hours. The amount of time spent submerged determines the thickness of the coating.

While aluminum naturally forms oxide on the surface over time, the aluminum oxide that is formed on the surface during the hardcoat anodizing process is more uniform, dense, and much harder than with natural oxidation.

Benefits of Hard Coat Anodized Aluminum

Hard Coat Anodized Aluminum is used for the following reasons:

  • Corrosion resistance
  • Aesthetics
  • Dielectric properties
  • Improved lubrication
  • Increased wear resistance
  • Increased abrasion resistance
  • Light weight properties
  • Flame resistance
  • Non-contaminating (for medical instrumentation)

How Does Hard Coat Anodizing Affect Dimensions?

It is important to note that hard coat anodizing parts with tight dimensions will affect their final dimensions. 50% of the coating penetrates into the surface of the parts, while the other 50% builds up on the surface. The typical thickness produced by hard coat anodizing is .0005”-0.002”, but the coating thickness can be controlled with exceptional accuracy using a state-of-the-art control system. When setting up a project, Arrow Cryogenics makes sure that the required specifications are included in the work contract documents. We work closely with our customers when tight tolerances are required to ensure that the thickness of the coating is exactly as expected.

How Does Hard Coat Anodizing Affect the Appearance of Aluminum?

If the aluminum to be hard coat anodized is not dyed (Class I), the color of the aluminum will change. The color of the aluminum after being hard coat anodized depends on the alloy and the thickness of the coating. On some alloys, the color of the aluminum after hardcoat anodizing will be gray/bronze; on other it will be gray-black. If the aluminum is dyed (Class II), black is the most commonly used color. Other colors may be available depending on the alloy and the coating thickness. Sampling is required if a color other than black is needed.

Sealing After Hard Coat Anodizing

After a component has been hard coat anodized, it may or may not be sealed. If the main function of the application is to obtain the maximum degree of abrasion or wear resistance, the coating should not be sealed. If the main function of the application is for corrosion resistance, and reduced abrasion resistance is not an issue, sealing is advised. If it is needed, the sealing of hardcoat anodized parts must be specified by our customers.

These are just a few of the industries that benefit from the standard anodizing and hardcoat anodizing:

  • Automotive
  • Aviation & Aerospace
  • Buildings & Architecture
  • Electronics
  • Food Manufacturing / Preparation
  • Equipment
  • Home Furnishing
  • General Manufacturing
  • Marine Industry
  • Medical / Dental Equipment
  • Military / Law Enforcement
  • Sporting Goods

Arrow Cryogenics is an ISO 9001:2015 and Nadcap certified for chemical processing company.

Please contact us for more information about our hardcoat anodizing services.