[rsimoes]

I was talking to my brother, who is an engineer in the auto industry, about the different Cobra replicas and the bare aluminum Kirkham's came up in conversation. He had an interesting statement and concern about the bare aluminum. He said that while it does not rust, it does corrode if left in bare form.

I told him the steps I had read about to take care of the car. However, he said that's fine, but how often would someone have to sand it or scotch brite the finish due to oxidation alone, even if it never saw rain and just sat in the garage.

And he shared this website with me:

http://www.teskoenterprises.com/aluminum.html

Which says the following about bare aluminum:

Advantages of using aluminum
Aluminum is a very lightweight metal, about one-third the weight of steel. It is very strong and exhibits a very high strength to weight ratio. It is a very durable metal, yet easy to work with and offers a no-paint maintenance ability.
It can be easily fabricated, formed, welded, riveted or bolted.
It does not rust. It is easy to work with and it produces a highly reflective, attractive, finish.
Aluminum is resistant to corrosion and attack by most chemicals. The dark gray oxide that forms on the outer surface of aluminum, unlike rust in iron, protects the basic metal. In iron, the basic metal will rust continuously.
If aluminum is subjected to a commercial process, anodizing, it forms aluminum oxide, one of the hardest man-made substances, through an electro-chemical process that thickens the coat of the aluminum, often from .5 mils to 6 mils. This increases the durability, and often, the visual appeal of the aluminum.
Most aluminum used in visible parts or applications is lacquered or coated, anodized or painted. Any parts that receive the most abrasion from traffic should be anodized. Anodizing's superior abrasion resistance will allow it to outlast paint on a door stile, kick-plate or push/pull bar, many typical applications. If the fabricated piece is to be used in a high use area, lacquering is not a good option, since it will be rubbed off.


Disadvantages of using aluminum
While it does not rust, aluminum will oxidize. This oxidation appears as white residue and pitting. Aluminum must be either powder coated or anodized to prevent oxidation. Mill finished aluminum surfaces will oxidize over a long period of time.
Aluminum can be water-stained easily. If the protective finish, or the bright finish as it is delivered from the mill is to be retained, proper storage of the material is a requirement. Aluminum can corrode quickly if suitable precautions against electrolysis are not taken and maintained.
Welding of aluminum requires specialized equipment and training compared to standard welding of steel.



Metal care tips for aluminum
Like stainless steel, aluminum is relatively resistant to corrosion. But it is very susceptible to attack by strong acids and alkalis used in some cleaning products. Also, it is very susceptible to galvanic corrosion - if aluminum and another type of metal are in contact with a liquid food that contains an electrolyte (e.g. salt), an electric current may form resulting in dissolution of the more active metal, which will probably be the aluminum.

Cleaning
Use a mild detergent and warm water when possible. Alkalis, even baking soda, and especially stronger alkalis discolor aluminum. If trying a stronger cleaner, pre-test on a hidden place to be sure it cleans satisfactorily and does not damage the aluminum. Always follow directions on the product label for aluminum, EXACTLY.
On outdoor architectural surfaces, remove bugs, sap, tree seeds, and other materials as soon as possible, as they harden with exposure to sunlight and heat, and become more difficult to remove. Suitable solvents will remove tar and similar substances. Test the solvent first if the aluminum is painted to be sure it doesn't also remove the paint. Make sure you follow the product label precautions when using solvents. Ensure that no spark or flame is in the area and make sure you have adequate ventilation.


What not to do
Avoid using abrasive cleaners (scouring powders, steel wool, abrasive polishes, etc.) since they can permanently scratch aluminum. Painted or anodized aluminum surfaces will be permanently damaged. Do not clean aluminum when it is too hot to touch, or if ambient temperature drops below 50° F.
Aluminum is so susceptible to corrosion from alkalis that aluminum panels should be protected from splashed mortar and cement.



So my question is, do you have any issues with bare aluminum oxidation like this? Or is it not an issue with the bare aluminum finish. If not, why not? Thanks!