First thing to understand when cleaning aluminum is the finish.

There are three types of finish that you will find in aluminum — mechanical (e.g., mill, satin, or polished), chemical (anodic) and organic (e.g., paint or wax).

The table below comes from the Aluminum Association and describes the designations for anodized finishes.

For many years, anodizing was the finish of choice for aluminum. The preparation of aluminum for organic finishes — paint or wax coatings — was difficult. Aluminum oxidization occurs quickly. Cleaning aluminum to remove this oxidization was critical to the success of a painted finish.

With the development of powder-coat and electro-static painting methods, painted aluminum has become more prevalent.

While aluminum does not rust, it will oxidize if the surface is not protected. Oxidized aluminum will come off as black when handled. This is not welcome in particular for handrails so keep this in mind when specifying your aluminum handrail. While going with a mill finish is appropriate for a low-traffic industrial area such as a waste water treatment plant, an aluminum railing in a high-traffic shopping mall should be anodized or otherwise sealed to prevent oxidization.

Once you understand the finish, refer to this document for information on cleaning aluminum: