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Standard Type II Aluminum Anodizing

Aluminum Anodizing for Metal Parts

Aluminum anodizing is a controlled electrochemical process that increases the thickness of the oxide layers that naturally exist on aluminum surfaces, improving corrosion resistance. These types of oxide layers provide insulation benefits and can be dyed with a wide range of colors. Anodized coatings also provide better adhesion for paint primers and glues and acts as an outstanding substrate for decorative finishes.

The most common method of aluminum anodizing, known as Type II, creates a finish up to 1 mil thick that is nonreactive, corrosion-resistant and easy to clean. Anodized coatings also provide better adhesion for paint primers and glues, and are used for numerous aesthetic purposes.

Arrow Cryogenics offers standard (MIL-A-8625 Type II) aluminum anodizing at our state-of-the-art facility in Blaine, Minnesota. We also provide hard coat anodizing (MIL-A-8625 Type III). Our anodized coatings can be customized to meet specifications requirements for coating weight, corrosion resistance, paint adhesion, and abrasion resistance. In addition, we have our own strict guidelines for appearance, workmanship, inspection, testing, and more.

Contact us to learn more about our aluminum anodizing options.

The Aluminum Anodizing Process Basics

The aluminum anodizing process is accomplished by passing DC electricity through an electrolytic solution in which the aluminum workpiece is submerged. The electrical current causes the release of oxygen on the surface of the aluminum, creating a buildup of aluminum oxide. The resulting anodic film is considerably denser than natural oxidation and is uniform across the surface of the workpiece. In short, aluminum anodizing is usually performed in an acid solution.

In short, aluminum anodizing creates an oxide coating that protects and enhances the look of the final product. Type II anodizing is best suited for aluminum, but it may also be used for nonferrous metals such as titanium or magnesium.

What Is the Difference Between Type II and Type III Anodizing?

Arrow Cryogenics offers two different options for aluminum anodizing: Type II standard anodizing and Type III hard coat aluminum anodizing. Both provide a protective barrier and are used for military specification MIL-A-8625 but there are a couple of differences you should keep in mind before selecting a process:

  • Type II standard anodized aluminum has a coating up to 1 mil thick and is sealed to seal in the dye and close the pores after the anodizing process for improved corrosion resistance. It is the most common form of aluminum anodizing and is available in dyed and non-dyed options.
  • Type III Hard Coat Anodized Aluminum is a thicker, more durable coating up to 2 mils thick. It is also available in non-dyed and dyed options. For the best wear resistance and when adhesion is required on a non-dyed component, it is typically not sealed.

Sealing is typically required after the Hard Coat Anodizing process is performed because the parts are sticky from the process. Sealing parts after the Hard Coat Anodizing process closes the pores, removes sticky residue and prevents unwanted material from sticking to the parts. Sealing is also required for dyed parts to seal the color into the aluminum pores to reduce fading.

How Does Aluminum Anodizing Affect Dimensions?

When anodizing aluminum parts with tight dimensions, it is important to understand that the coating will affect the final dimensions. In general, 50% of an anodized coating will penetrate the material's surface, and 50% of the coating builds up on the surface. The change in final dimensions is determined by the thickness of the coating. Using state-of-the-art controls, Arrow Cryogenics can control the thickness of our coatings with exceptional accuracy. We work closely with our customers to ensure that all tolerances are met.


Advantages of Standard Aluminum Anodizing

Type II aluminum adonizing is used for a wide range of applications ranging from computers to aerospace and has several advantages, including:

  • Corrosion resistance
  • Dielectric properties
  • Aesthetics
  • Better bonding
  • Non-contaminating (medical instrumentation, etc.)

Anodizing is also used to improve the look of finished aluminum parts. By using special chemicals during the pretreatment of aluminum that is anodized, we can achieve a satin finish that helps:

  • Blend machining and extrusion lines
  • Cover scratches caused during manufacturing
  • Reduce glare

Dyed and Non-Dyed Anodized Aluminum Colors

After anodizing, parts can either be left non-dyed (Class 1) or dyed in an array of colors (Class 2). Non-dyed aluminum will transform into grayish tone similar to what is pictured below.

Silver metallic aluminum color

Arrow Cryogenics can also achieve numerous colors by dyeing the aluminum after it is anodized. Once the aluminum is dyed, the color is permanently sealed into the aluminum to create a decorative finish. Below are some of the colors we have available to apply to anodized aluminum.

Note: Colors shown are for general reference only and may be affected by the color settings on your computer monitor. Other colors may be available upon request.

brown aluminum color
blue aluminum color
purple aluminum color
red aluminum color
black aluminum color
green aluminum color

Arrow Cryogenics' aluminum anodizing meets MIL-A-8625 spec requirements for Type II Class 1 (Non-Dyed) and Class 2 (Dyed) conventional aluminum anodizing process using sulfuric acid.

NADCAP Certified

Arrow Cryogenics is Nadcap certified for chemical processing and is in compliance with the AC7004 Aerospace Quality System for the Aircraft, Space and Defense Industry. As part of Nadcap accreditation, our processes were audited based on stringent industry guidelines and are regularly reviewed to maintain compliance.

Contact us to learn more about our Nadcap certification or to discuss finishing services for your aerospace application.

Contact Arrow Cryogenics for Type II Aluminum Anodizing

Arrow Cryogenics is ISO:9000:2015 and NADCAP certified for our aluminum anodizing services in a wide variety of colors and finishes.

Let us know you're interested in learning more about aluminum anodizing. If you're ready to start a project, provide us with some information about your application to get a quote.