Rust remover?
I built an electrolysis tank out of a 55 gallon plastic barrel. I lined the inside with thin stainless sheeting I found second hand. Fill it with Arm and hammer washing soda and water mixture (cost about $1). Then I hang what ever I'm wanting to derust with wire from a 4X4 block of wood that straddles the top. Hook up an elcheapo battery charger to the wire and the other to the stainless sheeting that lines the inside of the barrel and leave over night. Nice thing about electrolysis is the solution never goes bad and it will only remove the rust. Will never etch or stain anything and I've used my engine hoist before to drop whole blocks in and just hang it from the hoist while I'm running it.