alum tank refurbishing

[DRE]

It is susceptible to corrosion, true, but what I'm more worried about is 1) internal corrosion through moist gas, which you can catch by doing a visual, and 2) the use of dissimilar metals, such as putting a SS clamp on an AL tank (I personally always put a rubber band underneath). Granted, I don't dive a whole lot of saltwater, where it might be more of an issue, but I've never seen an AL corrode on the outside from use in fresh water.
I'd personally be more worried about polluting the water supply from paint (every little bit helps!) than the remote chance of external corrosion on my tanks. Also, in some of the more popular caves you can find paint traced on the cave walls from being hit by painted AL cylinders - one more reason not to have any paint whatsoever...