Rust removal with Electrolysis(pics inside)

that works also.
I have used heavy industrial cleaning (farming) detergent. those have acids and mixed with warm water will remove even heavy rust in a day.
stuff like this one:
http://www.delaval.com/en/-/Product...oducts/Consumables/Alkaline-detergents/Super/

its used to clean milking robots milk lines:)