What is anodizing aluminum and Process Benefits

Anodizing is a conversion coating process used to achieve an oxidized surface finish on metal components. It increases the thickness of the naturally occurring oxide layers on metal, enhancing the finished part’s corrosion and wear resistance. Compared to other finishing methods, such as painting or powder coating, the process results in a durable, long-lasting protective layer that is part of the metal rather than sitting atop its surface.

Anodized finishes have made aluminum one of the most respected and widely used materials today in the production of thousands of consumer, commercial and industrial products.

Steps of Anodizing Aluninum
Anodizing again might look complex, however, the steps are straightforward. Below are the general steps used in the anodizing process.

Step 1: First, cleaning of the aluminum part occurs before undergoing anodization. This is important for the removal of impurities that can hinder the process.

Step 2: Then placement of the material into a bath of electrolytic solution occurs and there is the application of a direct electric current. This creates a positive electric charge in the aluminum and a negative charge in the solution’s electrolyte plates. The resulting electrochemical reaction creates pores on the surface of the aluminum component, which enable the aluminum substrate to bond with the negatively charged O2 ions in the solution to create aluminum oxide.

Types of Anodizing
As I mentioned before, this article will reference MIL-A-8625 throughout to correlate with an industry specification. In this specification, there are three types and two classes of anodizing. The three types are as follows:

Type I
Type I and IB – Chromic Acid Anodizing
Type IC – Non-Chromic Acid Anodizing as a replacement to type I and IB

Type II
Type II – Conventional coating from a sulfuric acid bath
Type IIB – Non-chromate alternative for type I and IB coatings

Type III
Type III – Hard Anodize

Each type of anodize is used for a specific reason. Some of those reasons are:

Type I, IB, and II are used for corrosion resistance and some degree of abrasion resistance. For applications that are fatigue critical, type I and IB are used because they are a thinner coating. One example of this is highly fatigued structural components on aircraft.

Type IC and IIB are used when a non-chromate alternative is desired for I and IB. This is often the result of environmental regulations or requirements. When developing systems in the defense industry, new contracts often required environmentally friendly options (type IC and IIB) because of the presence of hexavalent chromium in type I and IB. However, it is possible to get waivers where required by geometry complexities and extensive re-qualification efforts.

Type III is used primarily increased for abrasion and wear resistance. It’s a much thicker coating, so it will outperform the other types with respect to abrasion and wear. This coating may reduce fatigue life, however. Type III anodize is frequently used on firearm components, gears, valves, and many other components that will slide relative to each other.

What Are the Color Options for Anodized Aluminum
Another thing to note on how to anodize aluminum is the color options available. This is because one of the most significant advantages of anodizing is the various colors options available. The standard anodizing aluminum colors include clear, bronze, champagne, and black. At WKproto, you have access to color cards with Pantone numbers from which you can decide the color you want.

Benefits of Anodizing
Anodizing is a common coating because of the numerous benefits it offers. These advantages include but are not limited to:
Durability – The wear and corrosion resistance extends the life of the parts which have been anodized without any chipping or peeling.
Health and Safety – The naturally occurring oxides produced during the process is chemically stable, non-toxic, and will not decompose.
Aesthetics – The availability of a virtually unlimited color pallet ensures a visually appealing surface.
Environmental – Parts that are recyclable remain recyclable after the process without stripping or other materials removal processes.
Ease of Maintenance – Parts that have been anodized can easily be cleaned with mild soaps and water without damaging the anodized surface.

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