How to clean burned-on food or grease

Fill pan with hot water and let stand 1 hour. Scrape off as much food as possible with a dull item such as a wooden spoon or half of clothespin, or plastic spatula or plastic sponge. Complete removal with soap-filled steel wool pad. For grease build-up, soak in very hot water with detergent; then scour with soap-filled steel wool pad.

Use mild a 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.

Be cautious about using abrasive cleaners (scouring powders, steel wool, abrasive polishes, etc.) as they may 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 temperatures go below 50 F.

On outdoor surfaces, remove bugs, sap, tree seeds, etc. as soon as possible, as they harden with exposure to sunlight and heat, and so are harder to get off. Suitable solvents will remove tar and similar substances. Test solvent first if the aluminum is painted to be sure it doesn't also remove the paint. Follow label precautions when using solvents - no spark or flame in the area and have sufficient ventilation.
Discolored Aluminum: Heat a solution of 1 tbs. vinegar per qt of water or 2 tsp. cream of tartar per qt of water in each pan until discoloration disappears.

Vinegar: To clean an aluminum coffeepot and remove lime deposits, boil equal pans of water and white vinegar. Boiling time depends upon how heavy deposits are.

Source  http://www.doityourself.com/stry/acidcleaners
This article has been contributed in part by Michigan State University Extension

Mary Findley spent 12 years professionally cleaning homes and answers your questions as moderator of our
DoItYourself.com Cleaning Forum . Visit her website at http://doityourself.com/to/goclean.htm for her free bimonthly cleaning tips.