Aluminum Anodizing Process

aluminum anodizing process

In the metal plating industry, aluminum anodizing pertains to electrochemical process wherein an oxide layer is chemically developed on the surface of the substrate. And while the main function of this layer is to act as an insulator, it is also beneficial aesthetically as this can be dyed in various colors. Thus, aside from providing the substrate protection from corrosion, it can also make finishes with excellent decorative properties.

Aluminum anodizing follows this general process:

The pre-treatment

The pre-treatment involves cleaning the substrate with a non-etching, weak alkaline detergent heated to about 145 degrees Fahrenheit. The very purpose of this process is to remove foreign matters, including accumulated contaminants such as grease or oil.


Rinsing follows after each process and usually involves multiple rinses; some metal anodizing companies use de-ionized water because it is free of mineral salts and thus can reduce the risk of smuts developing on the surface of the substrate.

The etching

In this process, a strong alkaline solution is used to remove a thin layer of aluminum, which gives the aluminum surface a matte appearance; the removal of thin aluminum is from micron up to one hundredth part of the surface, depending on the solution and the time of the etching process.


This step involves rinsing the treated substrate with an acidic solution to remove unwanted surface alloy/ other foreign particles not removed during the etching stage - this is commonly known as the removal of Ďsmutí layer.

The Anodizing

In this stage, Aluminum is immersed in a tank that contains an electrolyte having a 15% sulfuric acid concentration. This is where electric current is applied through the electrolyte; the Aluminum made the anode; the tank is the cathode, which allows the formation of aluminum oxide (Al203) after Voltage is applied.

Coloring / Dyeing

This process is done mainly for aesthetic purposes, where different colors can be applied through various coloring methods, including absorptive dyeing.

The Sealing

Lastly, considered to be one of the most important of all the anodizing processes, sealing is done to ensure that the pores on the treated substrate are non-absorbent, which is necessary to attain maximum resistance to corrosion and stains, and entraps the applied color.

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