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This article was reproduced with permission of Ted Kinsey, the original author. We had a lot of feedback on this Tech Tip and Randy Baumann compiled the additional information and prepared an update (June 2005 and again in May 2011 - a GREAT job!). It is available in a pdf format. Please support all copyright issues, we all work hard on that which we produce.
|By Ted Kinsey
What is the method?
Electrolysis is a technique for returning
surface rust to iron. It uses the effect of a small low voltage electric current
and a suitable electrolyte (solution). It has advantages over the old standbys
like vinegar, Coke, muriatic acid, naval jelly, wire brushing, sand blasting,
etc. Those methods all remove material to remove the rust, including un-rusted
surfaces. With many, the metal is left with a "pickled" look or a characteristic
color and texture. The electrolytic method removes nothing: by returning surface
rust to metallic iron, rust scale is loosened and can be easily removed. Un-rusted
metal is not affected in any way.
What about screws, pivots, etc that are "rusted tight"?
The method will frequently solve these
problems, without the need for force, which can break things. Is it safe? The
solutions used are not hazardous; the voltages and currents are low, so there
is no electrical hazard. No noxious fumes are produced. The method is self limiting:
it is impossible to over clean an object. Small amounts of hydrogen are emitted
in the electrolysis process. Good ventilation or an outdoor work site is all
that is needed.
SAFETY NOTE SAFETY NOTE
In March 2011, Derrick Willis sent in some additional information for this Tech Tip."The instructions on rust removal include the use of stainless steel for a sacrificial electrode. There is a good chance that your customers will be contaminating themselves with Hexavalent chromium. ( Erin Brockovich )." You may want to check the link he sent along on the dangers of hexavalent chromium.
Grigg Mullen, our Tech Advisor, suggested "many people feel using stainless steel as the sacrificial anode is dangerous to your health, and plain steel is a great substitute."
SAFETY NOTE SAFETY NOTE
Where did this method come from?
Electrolysis is a standard technique in
the artifact restoration business. I wrote this up for the Chronicle of the
Early American Industries Association a few years back. Most of the tool
collectors around here use it.
What do I need?
A plastic tub; a stainless steel (see box at right for important safety note) or iron
electrode, water and washing soda (Arm & Hammer, for example) and a battery
charger. About a tablespoon of soda to a gallon of water. If you have trouble
locating the washing soda, others have reported success with baking soda. Also
household lye will work just fine. It's a tad more nasty -- always wear eye
protection and be sure to add the lye to the water (NOT water to lye!!!) The
solution is weak, and is not harmful, though you might want to wear gloves. NOTE: It is the current that cleans, not the solution; nothing is
gained by making a more concentrated solution -- DON'T!
How long does the solution last?
Forever, though the loosened rust will
make it pretty disgusting after a while. Evaporation and electrolysis will deplete
the water from the solution. Add water ONLY to bring the level back.
What about the stainless/iron electrode?
The electrode wants to be large (within
reason); if possible, larger than the object being cleaned. The iron electrode
works best if it "surrounds" the object to be cleaned, since the cleaning is
"line of sight" to a certain extent. An iron electrode will be eaten away with
time. Stainless steel has the advantage (some alloys, but not all) in that it
is not eaten away. I have had good success with sheet stainless salvaged from
a paper towel dispenser. It has a large surface area and is easily shaped to
fit the container.
How do I connect the battery charger?
THE POLARITY IS CRUCIAL!! The iron
or stainless electrode is connected to the positive (red) terminal. The object
being cleaned, to the negative(black). Submerge the object, making sure you
have good contact, which can be difficult with heavily rusted objects. Get it
backwards and your object will be relentlessly eaten away! Make connections
on a part of your electrode that protrudes out of the solution, or your clamps
will erode rapidly.
How do I know if it is working?
Turn on the power. If your charger has
a meter, be sure some current is flowing. Again, on heavily rusted objects,
good electrical contact may be hard to make-it is essential. Multi-part objects
may not have good electrical connections between them. Fine bubbles will rise
from the object when cleaning is in progress.
How long do I leave it?
The time depends on the size of the object
and of the iron electrode, and on the amount of rust. You will have to test
the object by trying to wipe off the rust. If it is not completely clean, try
again. Typical cleaning time for moderately rusted objects is a few hours. Heavily
rusted objects can be left over night.
How do I get the rust off after I remove the object?
Rub the object under running water. A paper
towel will help. For heavily rusted objects, a plastic pot scrubber can be used,
carefully. Depending on the amount of original rust, you may have to re-treat.
The amount of mechanical action will depend on the fragility of the object.
Use your discretion.
My object is too big to fit. Can I clean part of it?
Yes. You can clean one end and then the
other. Lap marks should be minimal if the cleaning was thorough.
After I take it out, then what?
The clean object will acquire surface rust
very quickly, so wipe it dry and dry further in a warm oven or with a hair dryer/heat
gun. You may want to apply a light oil or a coat of wax to prevent further rusting.
Will the method remove pitting?
No. It only operates on the rust in immediate
contact with unrusted metal. What's gone is gone. What will it look like when
I am done? The surface of rusted metal is left black. Rusted pits are still
pits. Shiny unrusted metal is untouched.
What about nickle plating, paint, japanning and the
Sound plating will not be affected. Plating
under which rust has penetrated will usually be lifted. The solution is likely
to soften most paints.Test with a drop of solution in an inconspicuous place.
Remove wood handles if possible before treating.
How can I handle objects that are awkward to clean?
There are lots of variants: suspending
an electrode inside to clean a cavity in an object; using a sponge soaked in
the electrolyte with a backing electrode to clean spots on large objects or
things that shouldn't be submerged (like with lots of wood)
How can I dispose of the solution?
The bath will last until it gets so disgusting
that you decide it is time for a fresh one. There is nothing especially nasty
about it-it's mildly basic-so disposal is not a concern, except you may not
want all the crud in your drains.
Can I use metal containers?
This is highly risky. Galvanized metal
can introduce zinc into the solution. If you have used lye, it will attack aluminum.
You may have problems with electrical shorts, etc. Stick to plastic.
How can I clean odd shaped objects?
Be ingenious. Plastic PVC pipe and eave
troughs, wooden boxes with poly vapor barrier, kids wading pools, etc.
|Be sure to check out our extensive Forums discussions -- from General Truck talk, Electrical Bay, Big Bolts, Panels and Burbs, Engine and Driveline, Paint and Body, Interiors, Tool Chest -- The Stovebolt Collective can help in your quest and walk you through the mire and magic of working with old iron!