What is aluminum anodizing?

Aluminum anodized is the electrochemical passivation process by which the surface layer of an aluminum substrate is converted into an aluminum oxidation layer . While a natural oxide coating can be found on aluminum, this oxide layerr is often uneven, thin and offers poor protection. 

            Anodized aluminum sheets and components(Shunho metal solutions)

The controlled application of an electrical charge in an acidic electrolytic bath results in a very regular and uniform layer that has increased durability, and wear and corrosion resistance. Additionally, these anodic layers can undergo secondary processing to incorporate various functional materials, like colorants or lubricants.

                                     Aluminum anodizing workshop

There are lot of processes and standards that apply to aluminum anodized, the most common find their origins from the aerospace and automotive industries. In the U.S. (United States of America) the most often cited anodizing specification is the U.S. Defense specification MIL-A-8625 which defines three types of aluminum anodizing Type I – Chromic acid anodizing, Type II – Sulfuric acid anodizing and Type III – Sulfuric acid hard anodizing, with Type II and Type III being the most often utilized.

How are anodic coatings applied?

The anodizing processes involve submerging the aluminum parts into an acid electrolytic bath and then passing an electrical charge through the medium. A cathode is located on the outside of the tank, while the aluminum serves as an anode (hence the term anodizing). As the current moves through the bath, oxygen ions are released from the acid electrolyte and join with the aluminum components substrate producing the aluminum oxidation layer. It is very important to note that, unlike a paint or plating process, at the same time the anodic layer is fully integrated into the underlying substrate actually forming into and out of the substrate.

                    Anodizing production line(Shunho metal solutions)

                        Anodizing workshop(Shunho metal solutions)