Aluminium is a popular choice for bike plating, construction, outdoor furniture and even cookware. The alloy is naturally resistant against corrosion and can be moulded into a wide variety of shapes. But aluminium can develop problems over time, notably the build-up of scale and similar white deposits associated with oxidation. Aluminium corrosion can be cleaned off, but it is important to follow through and add protective layers to the metal when finished.
If you only want to remove recent stains from aluminium, or make sure that a deposit is actually a result of corrosion and not just a build-up of dirt, then you can try a homemade cleaner. Make sure you avoid baking soda, washing soda and other products with similar chemical structure. Aluminium in its natural state is very reactive to such substances, and if any of the sealant that protects aluminium has worn away, then using baking soda or a similar cleaning agent can cause permanent damage. Instead, try a traditional mixture of boiled water and vinegar, with a two-to-one ratio. You can also add or substitute a natural acid like citrus oil. If the aluminium pieces are small enough, soak them in the solution for an hour or two. If they are too large, just use a sponge or cloth to tackle the stains.
Aluminium corrodes, but very slowly, and instead of the red build-up of ferrous oxide that iron produces, aluminium oxidises to form a whitish layer that is its own form of rust. This whitish deposit can also be equally tricky to remove, and your best bet is to sand it away using a tough brush or sandpaper. Don't use steel wool, though, because the bits of steel and metal it leaves behind will rust in the traditional way and could make problems even worse. When the aluminium is clean and dry, add a protective primer or similar sealant. Aluminium comes with a factory sealer that allows it to resist the elements, and scrubbing the corrosion off removes part of the coat, so it is important to replace it. Sometimes, if aluminium is exposed to hard water, it can develop scale deposits that look like corrosion but are simply build-ups of calcium. Scrubbing may be the best way to remove these deposits too, but first try to soak the aluminium in a strong vinegar solution to loosen the mineral scale.