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Mark Rand

On 23 Nov 2008 04:01:42 GMT, (Old
Chipper) wrote:

I also use baking soda (sodium carbonate) for electrolytic cleaning. I use a
variable power supply so that I can control the current when de-rusting small
stuff, but a light bulb in series will work for a battery charger. assume
about four volts for the electrodes and drop the rest with a bulb. Due to the
constant current characteristic of bulb filaments, you won't be far off if you
assume a 5W bulb will give you .5A, 55W==4.5A etc. I use lead anodes because
they keep the solution cleaner than steel anodes. There is some lead carbonate
formed, but it's not a major issue as it's insoluble. Just don't eat it! Major
issue with stainless anodes other than worries about formation of hexavalent
chromium compounds is that they get inhibited by the current and eventually
stop working until the current is reversed or they are abraded.

For large objects that won't fit in a tank (lathe cabinets), I've used
phosphoric acid thickened with cellulose wallpaper paste with about 20% acid
by volume. This appears to be close to what Jenolite is. The advantage of
phosphoric acid over others is that it won't encourage further rust in
crevices. It is a fairly weak acid compared with hydrochloric and sulphuric
and the waste products are fairly benign. Don't pour it into the river, but
don't worry about diluting and watering the garden with it. It'll green up
your grass! Disadvantage is that the parts need scrubbing or pressure washing
to remove the crud that gets left on them.

Mark Rand
RTFM