3 hours isn't equal to 30 min.
Joe Hurst
>Todd-
I can't say that I was able to conduct the most scientific of experiments, but I since I was zapping these specimens at work, and was able to check their progress every hour or so, I think I was able to make some reasonable conclusions.
For starters, for badly rusted tools, 30 minutes isn't the same as 3 hours. Especially if your battery charger has a low and high setting (I used "low"). I noticed some bubbles, but little rust removal for at least an hour.
In particular, the frog and body required about 8 hours to look decent. In both cases, I'd visit the tub every 2 hours, rinse off some of the black oxidation, and then turn the piece so that the rustier side would face the anode.
The corrugations added up to a lot of surface area, and a lot of crannies that I didn't want to scrub. Instead, I left the body in the tub overnight. It worked quite well.
Electrolysis is a self-limiting process. Once the rust is gone, the process stops. If the process has stopped, the japanning is no longer in danger...at least no more than it was when the surrounding rusted metal was bubbling for the first two or three hours.
Of course, this is just my two cents. So much depends upon the tool (is it japanning, or was it painted? has the rust worked it's way under the nickel plating, etc.?). And you should consider the collector value of the tool (a 603 deserves more attention than a Craftsman #4). And since you are producing hydrogen, I wouldn't suggest zapping a hunk of rust, and leaving it to cook in an unventilated basement or gargage. Odds are nothing would happen, but there's no point in risking it.
As a conscientious user, I've found that even leaving bare metal parts (screws, threaded rods) in the bath over a weekend is still easier on the pieces than cleaning them with emory paper or navel jelly.
-J
