Aluminum Anodizing: A Winning Combination

by Joanna Dykhuis, IQS Editor

The Tour de France came to an end last week with Alberto Contador of Spain winning the 2,263 mile bicycling race for the second year in a row. In the second stage of the race, however, there was an incident that could have prevented him from even finishing. Contador, Lance Armstrong and many other riders experienced a massive crash when they encountered a road made slippery by rain and an oil spill. Most cyclists continued on after sustaining minor bruises and abrasions. Their bikes remained relatively undamaged because the material of the frame and wheels had undergone an aluminum anodizing process. This technique is used with both professional and hobby bicycles to harden the surface of the aluminum and thicken the layer of naturally occurring oxide, resulting in a tough, durable and corrosion-resistance finish.


Photos courtesy of  Anode, Inc.

Aluminum anodizing is an electrolytic passivation process where the aluminum is placed in a chemical bath to become the anode of an electrical circuit. The acid bath takes on the opposite polarity and when a current of electricity passes through the bath, the surface of the aluminum oxidizes, essentially rusting. Unlike iron which flakes and grows weak when rusted, oxidized aluminum gains a strong coating on the surface that is extremely hard and resistant to corrosion and wear. Bikes are not the only objects that receive such treatment. Anodized aluminum is frequently used for pots, pans and other cookware in addition to manufacturing equipment, protective cases for electronics, exterior surface panels, satellites and a plethora of other items.

Photos courtesy of Aluminum Shapes, LLC and Superior Metal Technologies, LLC.

Anodizing is not limited to just aluminum but can be performed on a variety of metals. Titanium anodizing produces metal with similar characteristics to anodized aluminum. Generally speaking, however, among anodisers aluminum is favored because it is otherwise prone to corrosion. It is also one of the most lightweight metals which is beneficial for cyclists who bike through mountains and across countries. Different processes are used to achieve different results and there are three main kinds of anodization used with aluminum: chromic acid anodization, sulfuric acid anodizing and hard anodizing. Other options are more concerned with the appearance of the part. Color anodizing is favored among cyclists because it allows riders to customize their bikes. Practically any color is possible and some formulas may actually improve corrosion resistance. Clear anodizing produces a transparent film on the material for less visual applications.

Anodizing is a very useful process that contributes to the performance and appearance of aluminum and other metals. It has a wide range of capabilities and options which is a contributing factor to the popularity of this practice. There are other similar processes that are sometimes used as alternatives such as chromate conversion where the electric conductivity of aluminum remains intact instead of being changed by an anode. Most comparable processes retain the essentials of aluminum anodizing and are often categorized as such. Anodizing is a greatly beneficial process that helps everyone from industrial companies to Spanish cyclists become winners.

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