[bubblegumpi]

I see on youtube videos people using 12 volts attached to a rusty object then putting NaOH into the water to remove the rust. How does this work? Does it matter which polarity the part is? Does the NaOH take part in the reaction or does it just work as electrolyte, if so why not use cheaper safer NaCl? Would reversing the polarity make rust? I know that when things rust essentially a microscopic battery is formed at each rust spot is this the reverse?

[chenbeier]

It is a Physical Effect. The NaOH gives conductivity. At die electrodes hydrogen and oxygen is developed. The Gas Bubbles remove die Rust. NaCl cannot be used because Cl^- creates chlorine which etches the iron.