I am at a residence doing some work and noticed that around their pool the boxes, switches etc. are all seriously coroded. Is this do to electrolosis or chlorine in the air?

Probably due more to the airborne Cl than electolysis or "galvanic action" (dissimilar metal contact).

Unless you go to Haz Atmosphere hardware ($$$$$$$$$) it's probably just another "unexpected incidental cost" of having a pool.

Alternatives to Haz Loc material (which just might end up being aluminum, too) would where applicable be iron "FS"/"FD" boxes or nonmetallic boxes...S

I figured it was the clorine also but I don't recall seeing this before, of course I don't do pools so its probably normal.