I've experimented with PBW, oxyclean, and a oxyclean TSP (sodium metasilicate) mix in an old aluminum turkey fryer pot I no longer use.
I've found that, at least at suggested mix ratios, none of the above cleaners pit or damage the aluminum for at least 10-15 minutes. I haven't tried any longer than that. When mixed with hot water that contact time seems sufficient to remove pretty much all gunk hanging around. Honestly, hot water and a brush is usually sufficient to remove 98% of everything left in the boil kettle.
To hear people talk, PBW would eat through aluminum like acetone through a stryofoam cup. That's not true in my experience. The PBW will blacken the pot if it does anything but I've found that wort itself will (and has) done that.
Perhaps you're making the solution ridiculously strong and/or letting it soak for hours or overnight.
I have a 20gal aluminum kettle I plan to use in the new rig and plan to do CIP based on the aforementioned tests I've done with my old turkey fryer. Do what you like and if anyone ruins their pot with PBW, don't blame me. Caveat emptor.