Eventually the air quality around bare aluminium surfaces causes the aluminium to oxidise. Oxidation makes the aluminium look cloudy, like it has a layer of dried milk or water on the surface. Fortunately, oxidation does not pit or leave dents in the aluminium surface. When removing oxidation, avoid the use of harsh chemicals. They can cause premature wear of the aluminium surface and get embedded in the pores of the aluminium.
Wash the aluminium surface with clean, soapy water and a rag, and then dry it thoroughly with a cotton towel. If your aluminium object is a cooking item, like a pan, get all of the baked-on food off the bottom by boiling water in the pot for five minutes and then by scraping the old food off with a wooden or plastic spatula.
Place three drops of white vinegar into a boiling pot of water and submerge your aluminium item into the pot if it is small enough to fit. Allow the item to rest in the boiling water for 15 minutes. This helps to remove oxidation. If the aluminium item is the pot, simply fill it with water, add the vinegar and boil the water for 15 minutes. If the item is too large to fit into a pot, go to step 3.
Wet a rag with lemon juice and sprinkle it lightly with table salt. Buff the surface of the aluminium with the rag. The lemon acts as an acid base to remove the oxidation, and the salt acts as a mild abrasive to help remove the oxidation build-up. Do not scrub too hard, as the salt can scratch the surface.