I wouldn't put an unknown chemical mix into aluminum, lots of acids react with it ... why 120*? was it that hot when you did it before? could always get some type of barrel heater to wrap around the tub or an immersible heater

I'd just use electrolytic derusting, washing soda and a battery charger grin

Bill

Moved over to the Passing Lane

"When we tug a single thing in nature, we find it attached to the rest of the world" ~ John Muir
"When we tug a single thing on an old truck, we find it falls off" ~ me
Some TF series details & TF heater pics