I am fond of electrolytic derusting. I do it a lot. I have collected a bunch of little tricks I use but this one is good enough to write up and share. Like lots of home shop guys, I use an inexpensive car battery charger. Mine is made by Schumacher, and has only one control, a toggle between 6 and 12 volts. It does have an ammeter. It's a 10 amp battery charger with overtemp protection. What happens when I go overcurrent for very long is a relay clicks and then I have to wait a bit for the thing to cool down and start over.
What I have found that in midwinter, outdoors but under the eave of my shop front overhang, in 20-30F temperatures, I can run it at nearly 18 amps for several days in a row now without its overcurrent relay popping and without the charger seeming to even get warm.
Well, now that I've written it this trick seems dead obvious, but believe me it wasn't to me before I learned it! :-)
Grant Erwin Kirkland, Washington