What is Anodized Aluminum and Everything You Should Know About Anodizing Aluminum | CNCLATHING


Anodizing aluminum is an excellent choice when requiring professional aesthetic appearance and great mechanical properties of CNC parts. As a popular post-processing method, anodizing can not only be applied on aluminum, but also suitable for many other metals. CNClathing.com provides an extensive of surface finishing services, you can utilize our aluminum anodizing to improve the mechanical capabilities of your metal parts. Here is an overview of anodized aluminum and anodizing process to introduce what you should know about the technique. 

What is Anodized Aluminum?

Anodized aluminum is the aluminum with an anodized layer, which is created through an electrolytic solution where the metal is immersed in, the anodizing layer is grown from the metal itself. With the layer, anodized aluminum got enhanced visual effects and functions. Anodized aluminum is exceptionally durable, and much harder than the raw material but lighter than stainless steel and copper, remaining the natural luster, texture, and beauty of the metal itself, will not chip, flake or peel, and never wear in normal conditions. 

Advantages of Anodized Aluminum

The oxide layer formed in the anodizing process can effectively improves the corrosion resistance and other properties of metal parts, and simultaneously enhances the visual quality. The benefits of anodized aluminum can be summarized as follows:

– Better adhesion for paint primers and glues

– Retains the natural appearance of the material

– Keep the part from being scratched

– Exceptionally durable and hard

– Increased abrasion and corrosion resistance

– Prolong the service life of aluminum parts

– Terrific thermal insulation

– Its coating is much thinner than paints and powders

– A wide range of colors can be applied on the surface

– Environmentally-friendly

How Does the Aluminum Anodizing Process Work?

Aluminum anodizing is a process to electrolytically coat the aluminum surface with a protective or decorative oxide. When the aluminum CNC machining parts or material is submerged in the electrolytic solution, the electric current releases oxygen on the surface of aluminum, forming the accumulation of aluminum oxide. Introducing the electrochemical process, the current makes the positive ions be attracted to the negatively charged plate, while the negative ions attract to the aluminum part, which is the positive anode. The electrochemical reaction forces the pores on the surface of the aluminum to open and positive ions to escape. These holes drill down into the base of the part. A barrier layer is formed by the combination of negative ions and aluminum surface. The resulting anode film or layer is much denser than natural oxidation, and evenly distributed on the workpiece surface, make the aluminum parts resistant to corrosion. The electrolytic solution is usually an acid solution, such as sulfuric or chromic acid.

How to Anodize Aluminum?

Before aluminum anodizing, the aluminum parts should be cleaned and rinsed. You need to prepare an acid solution, distilled water, tanks, aluminum parts, battery charge, and more items. Check out our articles for how to anodize aluminum at home.

Types of Anodizing Aluminum

Type II anodization is best suited for aluminum, but it may also be used for nonferrous metals such as titanium or magnesium.

– Type I: use chromic acid to produce a thin and ductile anodized layer on an aluminum part

– Type II: use sulfuric acid to produce a thicker anodized layer on metal part, better for coloring

– Type III: hard anodizing, also use sulfuric acid, keep supplying the electrical current until the depth of the pores exceeds 10 microns, offers greater corrosion protection and wear resistance 

How Do You Add Color to Anodized Aluminum?

You can add color to anodized aluminum through several methods.

1. Dye: immerse the anodized aluminum part in a liquid solution that contains a dissolved dye, the porous anodic coating will absorb the dye. 

2. Integral coloring: combines anodizing and coloring to both form and color bronze and black shaded oxidation cell walls.

3. Electrolytic coloring: immerse the anodized aluminum part in a bath contains an inorganic metal salt then apply current.

4. Interference coloring: modify the pore structure produced in sulfuric acid and enlarge the pore at the base, metal deposition at this location produces light-fast colors due to optical-interference effects.

Can the Whole Part be Anodized Completely?

No, the entire part can’t be anodized completely. For the anodizing process, the part needs to be mounted on some type of hanger to keep it from falling to the bottom of the tank and in position. No matter where the fixture contacts the part, that area will be blocked and can’t be anodized at one time.