The anodizing of aluminum products has a very simple and practical purpose: to protect against corrosion or rusting over time. Anodizing does not, however, increase the tensile strength of aluminum, nor does it provide any other sort of quantifiable increases in atomic structure.
The process of aluminum anodizing is fairly straightforward, from an electrochemical standpoint. The aluminum object to be anodized in placed in a chemical solution (typically sulfuric acid), and then an electrical charge is applied. The resulting electrolytic passivation process causes the surface layer of the aluminum to oxidize, becomes noticeably more porous in texture, and thereby more adherent for subsequent additional painting and/or metal plating.
This process also means the treated aluminum is less likely to crack from normal aging and wear (from typical use or exposure to intended environments). Because this process requires complete submersion, it is usually beneficial for aluminum product designs to include natural contact points where it can be safely lowered and raised from the sulfuric acid solution. The contact points prevent the possibility of anodizing the entire surface of the aluminum.
Aluminum tends to be one of the best metallic candidates for this type of process, as it is light, strong, and relatively inexpensive. Other potentially viable alternatives are titanium, magnesium, or zirconium. However, these metals tend to be much more expensive than aluminum, and therefore can be less cost-effective for large-scale projects. Ferrous metals, such as iron and carbon steel, aren't generally well suited for anodizing treatment, as anodizing is essentially a form of oxidation, and ferrous metals rust when oxidized. Therefore, when ferrous metals are subjected to the same anodizing process, the oxidized surface layer becomes brittle and gradually sheds.
The process of anodizing aluminum in sulfuric acid changes the crystal structure of the aluminum's surface, making it more porous and better at bonding with paints, dyes, or additional metal treatments. Therefore, it is very common for dyes to be added directly to the sulfuric acid mixture to anodize the aluminum and provide a strong color treatment at the same time. This procedure can be advantageous as it both creates a far more cohesive surface structure, and is more resilient in maintaining its appearance over time.
Aluminum parts can be anodized by suppliers through a number of services, in virtually any size or shape. This means that objects from the size of large-scale industrial applications to miniature internal moving parts can all be anodized successfully. Contact aluminum anodizing services to learn more.