An untreated aluminium profile has a durable and corrosion resistant surface by nature. By suitable surface treatment you can, of course, improve the corrosion resistance even more.
Even if the material is resistant by itself, corrosion can occur. Read more about pitting - one of the most common forms of corrosion.
Read more about design tips - preventing pitting here
Crevice corrosion is another type of corrosion which can occur if you do not handle aluminium properly.
Read about crevice corrosion >>