remediate corroded fins on AC, if it possible - how?
A non acid foaming coil cleaner is your best option at this point. Once the fins are gone the coils will still exchange some heat but not be very efficient. R22 is getting very expensive ( around $100 per pound) . Since the coils are damaged cleaning all 3 sides will help the system Cool possibly for a few more years. I would not try to add epoxy or other adhesives to the coil. Cleaning with a foaming cleaner and low pressure water (no pressure washers) just a garden hose may stop the corrosion and improve the condenser coil's heat exchange.