Electrolytic rust removal is using a bucket, some washing soda and a battery charger to remove rust. Just did it for the first time today and it is working great, makes the parts look new again and does no damage to the part. here is a link: http://www.stovebolt.com/techtips/rust/electrolytic_derusting.htm
I will be coating with high temp stove paint after using a Ospho type coating for primer. since I will be using it for a hot tub and the water has bromine, I’m also going to put a sacrificial zinc anode in the piping leading to the heater to protect the coils. No iron in the plumbing either, it’ll be all brass or copper. I’l send you a pic when done if you want to add it to your gallery. I’d never have figured out the make and year of this heater without your gallery pic.