the oxidization of metal is commonly called "rust". When aluminum "corrodes" it is the same as oxidization, which is the same as rust. Aluminum just takes longer to be effected by oxidization. Steel or iron rust is red or brown aluminum rust is white.
Don't forget, aluminum is also "protected" by an oxide layer. When that layer is removed (polished/sanded/or weathered) a new oxide layer has to form due to oxygen having direct contact with the aluminum molecules. This oxide layer is actually pretty tough in the grand scheme of things, which is why it usually has to be mechanically removed from aluminum before welding, etc. Sure, some use a mild acidic solution...
Aluminum corroding (severely) really accelerates at a certain point. When that oxide layer gets thicker and rougher, it then holds corrosive fluids, salts, minerals, easier, which further speeds up the process, making the layer even thicker, possibly even minutely flaky, ehich then holds more material. Although that takes many, many years in most cases. A clear coat over the aluminum can also speed this up by holding material under it once it starts cracking/chipping. You see this on rims/wheels quite a bit. It really is similar to steel in the way it corrodes, but on a much finer visual/molecular scale. We see this often on aluminum intake manifolds and old aluminum distributors at the junkyards. After cleaning or blasting we're left with large semi-circular pits as a result. Being in constant contact with water really accelerates this as well. Especially salty or hard water.
GB
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