To fix and stop the corroison you need to get out the brillo pads, phosphoric acid and chromic acid and then seal it
with a good primer. You can buy this from Wicks (Germany?) or Spruce (England?) here it will cost about $20 for
enough to do several airframes with both materials. You might also be able to get it in automotive versions from Sikka
or what ever brand you have locally. Use that as a last resort, it works but you may have to do more work to get
the same effect. This will stop and fix the corrosion unless it is so bad that the structure itself is weakened by
the corrosion and at that point you need to make new parts.
 
Phosphoric acid is commonly called "Metal Brightener" and is used to clean the surface. You gently scrub it over the
aluminum then rinse off with distilled water. 
 
Next you use the Chromic acid to convert the oxidization to chromic oxide which is stable unlike the aluminum oxide
which keeps on eat the aluminum. Chromic acid is also known as ALODYNE and a few other simulaur commercial
brand names. Various brands will leave the metal a gold colour after conversion some will just leave it a dull gray.
 
At this time you can leave it as is or spray some good primer preferably chromate if you can get it and paint if its
outside and you want the cosmetics to look as good as you can get.
 
Wax's and polishes are not that good for protection. It helps a little, but really only slightly slows the corrosion down.