WORKSHOP
forming on the surface. If not, check your connections. You may need to scuff the rust where the
object touches the hook. Depending on the amperage of your DC supply, a full treatment may take
up to 1 day or so, but you can’t damage an item by
leaving it in too long.
5d. Remove the object and dry it. The visible scale
and surface rust will have been converted to a black
powder that can be removed with a wire brush, wire
wheel (Figure J), or light abrasive blasting. This
oxide dust doesn’t cling to the metal like rust.
5e. Treat the object with a phosphoric acid and zinc
prep solution. The acid removes any flash rust left
by the bath, and the zinc protects against future
rust and adheres well to primer. Dry, prime, and
paint or clear-coat the object as soon as possible.
Hints and Notes
» The electrolytic bath is basic (caustic), like lye,
so wear goggles and rubber gloves and keep
a bucket of water or a hose nearby in case you
spill or splash some on yourself.
» Alligator clip cables work well for suspending
small parts like nuts and bolts from the hook.
» Painted rusty objects can take much longer
because paint impedes electricity. For better
results, scratch up the paint first, or use a paint
remover before treatment.
» Ordinarily, you can dispose of the used bath liquid
down the drain. But if you removed lead paint or
you suspect that heavy metals (chrome in particular) have leached from your items, let the water
evaporate to form a sludge (not a dust!) and bring
it to a local toxic materials processor.
5f. Before painting or coating, mask off any gear
shafts, keyways, or other high-tolerance fittings,
and swab gear faces and other working surfaces
with oil so you can wipe the paint off later. A metal
detailing finish can preserve the metallic look, and
for antiquing and other effects, miniatures catalogs
carry a spectrum of paints for die-cast figurines.
Before applying a clear coat, it’s very important
to remove all oils and other potentially corrosive
materials. Brass, copper, and smooth cast iron are
particularly sensitive to the acids in finger oils,
and you don’t want to have a fingerprint showing
up months later! Wearing plastic gloves in a well-ventilated area, apply acetone or another thin
evaporative mineral spirit.
You can coat with Rust-Oleum spray, or try
POR- 15 Glisten PC for more durability. For enclosed
gears and mechanisms where dust isn’t a problem,
you can also coat parts with way oil, a heavyweight
oil used to grease machine tools.
Resources
» Metals Handbook, Volume 5: Surface Cleaning,
Finishing, and Coating, American Society for Metals,
various editions and years — an excellent general
reference
» Wolfgang Jordan’s Small Tool Museum
explains the chemistry of electrolytic conversion:
xrl.us/rustremoval
» Bill’s Antique Gas Engines explains the chemistry
of electrolytic conversion: antique-engines.com/
electrol-details.asp
John Todd is a networking-and-VoIP Dr. Jekyll during the
workweek, and a diesel-and-steam Mr. Hyde on the weekends. He’s currently building the world’s most over-designed
vegetable-oil-powered home electric plant, and he manages
the freenum.org alternate telephony numbering system.
Disc Sander Cover
I don’t often use the disc section of my big
belt/disc sander, so I made a simple cover
so I don’t have to worry about things (or me)
falling against the rotating disc when I’m
concentrating on using the belt.
—Frank Ford, frets.com/homeshoptech
152 Make: Volume 17
Magnetic Pocket
Toss one of those strong neodymium magnets in your
pocket, and you can stick a whole load of screws or
nails on the outside for easy access when you’re doing
a bit of shop maintenance.
—Frank Ford, frets.com/homeshoptech
Find more tools-n-tips at makezine.com/tnt.
