Alot of PA 28 Piper's have evidence of old paint stripper from repaints that get into the spar carry thru. It can be clean up & zinc chromated then coated with dintrol or lps 3. Avoid removing the bolts or wing if possible just the very heavy rusted ones if they don't clean up. Bolts are close...
Any time you drive the wing bolts out or in your scratching the bore of the holes in the spar causing stress risers. A previous AD pulling wings did more damage then good. I have seen the washers installed digging the sharp edge in the spar causing a stress riser. Most Piper Arrows will show...