The reason Aluminum always seems to look bad after a couple quick months of being outside is because of oxidation. The scientific description goes like this...
A reaction in which the atoms in an element lose electrons and the valence of the element is correspondingly increased.
Now the laymen description...
The combination of a substance with oxygen.
We can bring it down another step and just say, Why does all my custom aluminum stuff on my truck look like crap?
This is probably the universal way of describing oxidation if you purchased certain aftermarket pieces when they were all clean and shiny, then they turned dull and crusty.
There are ways to bring back the cleanness of the aluminum and it is relatively easy. The shine will have to be buffed or hand rubbed to bring back. Anyway, the first way to remove oxidation is a home recipe that we all probably have the ingredients for in our kitchens.
These ingredients are:
• Mild dish liquid
• Lemon juice or vinegar
• Latex gloves
• Eye protection
• Scratch-resistant scrub pad
• Soft cloth
Removing Oxidation #1
The steps to clean oxidation off smaller items is as follows:
Remove dust and dirt from smaller items, such as pots, pans, utensils or decorations:
Soak your aluminum item in a sink filled with hot water. Gently scrub the items with mild dish liquid, rinse and dry thoroughly.
Prepare the acid wash:
Fill a pot with 4 cups (.95 liters) of water and 2 tbsp. (30 ml) of lemon juice or vinegar.
Bring the acid solution to a boil:
Allow the solution to remain at a high boil for 15 minutes. While the solution is boiling, place all aluminum items in the pot.
Drain the solution:
Carefully remove the pot of boiling solution from the heat and drain it, along with the items, into the sink.
Rinse the items thoroughly with warm water:
Check the aluminum items, and repeat the process if the stains aren't removed.
Removing Oxidation #2
Now the way I like to clean the metal is a bit faster, easier, and requires a little more attention. This is by using acid wash. You probably have past by a truck yard or two and saw them using power washers on the trucks to clean them. Well, this is usually the last step to cleaning them. The first step is usually shooting a concentrated mixture of acid and then rinse away the oxidation and acid with power washers. There are different acids used in this process and here are they are.
Depending on your materials, these can clean Aluminum and Stainless Steel, even fiberglass pretty darn good. Get anyone of them on your skin, even as a mist will cause discomfort rather quickly. I'm sure breathing them on a regular basis is not good for you either. There are economical mixtures and foaming mixtures, anti-streaking mixtures and even mixtures to clean off yellowing boats. Some can be applied in drive through archways and some are power sprayed. All depends on your application. The strong mixtures contain all 3 acids and also cleaning agents to do the job. There are also rumors that say that these chemicals will destroy metals when using them to clean with, but technology has helped to remove this problem almost completely. If you don't rinse the metal off thoroughly, of course you will get some amount of break down, but just use common sense and wash everything completely of the acids and you will be fine. These chemicals are available and some can be found right in your own hardware stores as cleaners. They are by far the best for cleaning oxidized metals effortlessly and are reasonably affordable.
They usually carry the names ALUMINUM BRIGHT or ALUMINUM BRIGHTENER. Always check the back label for proper use and wear eye and skin protection when using any type of acid based chemicals.