What current and voltage are best for electrolysis rust removal?

I weld carbon steels all the time, and sometimes I get parts from the scrapyard. Unfortunately, these parts are generally oxidized, so I've been assembling an electrolysis tank for it. This tank removes the oxidation in about a day. I'm getting the feeling that I can make it go faster if I step up the current or voltage. What combinations of currents or voltages would make the fastest method of removal?

NOTE: I'm familiar with the risks of doing electrolysis, including hydroxy production, and the restriction on stainless steel electrodes.