Another source of sodium hydroxide - which by the way when added to a bucket of water makes a great paint remover, is septic tank main line cleaner from the hardware store. I had to give about $10 for a gallon.
I have a pair of fog light buckets that will come out in bare metal and ready to paint in the morning. If it has rust and paint, add a battery charger and it will pull the rust off. see electrolysis.
