Advantages of Aluminum Anodizing Technology

The fast growth and widespread use of aluminum since World War II is coupled directly to the ability of anodizing processes to defend it from corrosion, improve its appearance by brightening it and offering a rainbow of colors, and also imparting ceramic-like toughness to its outer skin. Hydrated aluminum oxide is the steady form of aluminum in nature; so, unprotected aluminum exposed to air and water would corrode, forming a broken, powdery, white corrosion product. This growth of natural oxide, if not checked, will proceed as long as unreacted aluminum is exposed. It can actually be envisioned as an accelerated corrosion procedure; the difference between anodizing and the natural process is that anodizing forms a denser, constant, oxide layer.

Anodizing has numerous benefits over other coating choices. For instance, while plating and painting to protect aluminum, there will be always a barrier between the coating and aluminum substrate with these methods; the only bond between the two is mechanical. If the bond in this obstacle region is compromised by way of poor substrate preparation, mechanical damage likes scratching or gradual degradation (e.g., general corrosion), raw aluminum would be exposed and corrosion can commence.

Anodizing, on the other side, is a conversion coating method that results in a chemical link between an anodic aluminum oxide layer and the aluminum basis material, which is stronger than a mechanical bond. While painted or plated coatings over aluminum can be peeled away fastly, there is no means to separate the anodic layer from the aluminum on which it is formed. In addition to the bonding matter, paints and plated metallic layers are very softer than aluminum oxide. On the well-known Moh scale of mineral hardness, one type of naturally occurring aluminum oxide, that is corundum, is the ninth hardest out of ten. The only mineral that is harder is diamond! Keeping this in mind, it's not surprising to learn that a constituent coated with the hardest plated metal (specifically hard chrome) will wear more readily than a like component that is hard coat anodized.

Finally, the mechanism of oxide growth during anodizing process results in a porous structure. This will permit further surface modifications such as:

-Dyeing to pass on nearly any color to the anodic layer
-Sealing with a lubricative stuff such as molybdenum disulfide or PTFE
-Infiltration with an adhesive for bonding applications

These factors, together with the fact that anodizing is much more economical than either powder coating or plating, point to the continued significance of anodizing as the coating of choice for aluminum in a broad range of applications. The strongest growth category for this aluminum appears to be that in the field of transportation. An estimated increase in the production of new aircraft to restore aging fleets and the auto industry's trend of raising the use of aluminum for the vehicle frames and bodies are likely to be the primary drivers of this growth. Another large category, architectural aluminum, does not seem to appear to be poised for large growth; in fact, this market might already have reached its peak.