How does anodizing increase the corrosion resistance?

Anodizing of aluminum alloys and die-cast zinc

The Anodizing of aluminum alloys and die-cast zinc is an electrochemical process that creates a protective layer on the surface of the treated metal that protects against corrosive substances.

In addition to improving the corrosion resistance, aluminum anodizing is typically used to increase the surface hardness, and thus the resistance to wear and abrasion, but also to create better thermal insulation of the workpiece, or to improve other properties, such as gluing or painting . In other cases, it can also be a simple aesthetic choice.

The Anodizing of aluminum alloys and die-cast zinc is a forced electrochemical process with which a rust protective layer is formed on the surface of the treated metal and protects it from corrosion.

The anodizing process is mainly used for aluminum. An actual surface deformation occurs in the material: the bare metal reacts with oxygen, which develops during the electroplating process and forms aluminum oxide. Similar processes are available and can also be used for titanium, zinc, magnesium, niobium, zirconium, hafnium and tantalum.

What exactly is that Anodizing of aluminum alloys and die-cast zinc?

When an electric current is supplied from an external electrical circuit (cathode) and circulated through an electrolytic cell in which the aluminum is immersed in an aqueous solution, it acts as an anode (positive pole), carrying negative ions (anions) through that form fission, especially of oxygen, migrate through the attraction between the opposite charges, towards the positive anode, aluminum, on which the electrical charges decrease. The deposited layer on the surface turns out to be a layer of aluminum oxide formed by an electrolytic process.

Essentially, the anodized aluminum surface is characterized by an electrochemical treatment that covers it with a thin layer of oxide that protects it from corrosion.