<VV> electrolytic cleaning and derusting

[kenfran at comcast.net]

I have been using this method to clean ancient coins (1500-2000 years in the
ground, made of bronze, brass, or silver) and it works fine, with no erosion
of the good metal. It even removes miscellaneous crud, dirt, etc. from the
coins. Grease is, as reported, bad for this method because it does not
conduct well, so the electricity can not get to the surface of the metal. I
use salt for my solution, mainly because it is already in the house and I
don't need to go out to buy something. The purpose of the salt or washing
soda, etc., is just to make the solution conduct electricity, so as long as
it is a decent conductor, a lot of chemicals will work. One note of
caution -- USE PLASTIC or other non-metallic container. You dont want to
have your container eaten up.
Repeated word of caution -- use WELL-VENTILATED area.
Also, the voltage is not that important, as long as it is at least 9 volts
or so, and a small power supply from a cell phone charger, etc. of even one
amp will work,  (MUST output DC, not AC) although not as fast as a 10 amp
car battery charger, especially for large pieces. If you have a computer you
were going to junk, remember that it has a power supply that outputs both 5
volts DC and 12 volts DC, so that would be a good power source. (This power
supply also makes a nice power supply for bench testing of car radios and
other electical gadgets)
Stainless or aluminum will get eaten up quickly. For the sacrificial
electrodeI usually use old stainless knives, forks, or spoons, which can be
gotten really cheaply from broken sets at thrift stores or yard sales. (I
don't need big pieces  for coins, and you might not for small Corvair parts
too. But stainless pots are easy to find in yard sales and thrift stores
too.
Also note that this is a good cleaning method before powdercoating, since it
leaves a nice conductive surface.
If anyone has tried powdercoating without cleaning off the black layer, it
would be good to know whether cleaning this is necessary
to avoid later rusting.

Ken Franson
1966 Monza 4-door PG 110
1965 Corsa 140 coupe, awaiting much work

> >also, you can use normal table salt, but water
> >softening or sidewalk salt does MUCH better....and
> >it's cheaper too.
> I have never heard of using table salt in any derusting solution! My >
notes on the topic gathered over the years suggest using common >WASHING
SODA instead. Following are my notes on the topic >from this and other
forums-----Wade Halsey
>
> "Anyone restoring a rusty old car should learn about this type of >rust
removal. It uses chemistry to make work easier. You will need >a large
container to hold the solution, a battery charger such as a >10 amp,
sacrificial piece of steel, such as a section of stainless sink >because
stainless lasts longer. Or use an old stainless pot or pot >lid. You want a
piece of steel with a lot of surface area. Then some >washing soda from the
grocery store.
> Fill the container with water and add one tablespoon of washing >soda per
gallon of water, more soda is OK. Put the steel in the >water and put the
red or positive (this is important) clip from the >charger on the stainless
steel. Keep the clip out of the water since >it is made of copper and will
disintegrate fast. Take the rusty part >and put it in the mix and attach the
negative clip to it. If the clip >goes in the water it's OK. Plug in the
charger and wait. Don't let >the part and the stainless steel touch. You
will see bubbles start to >come off the part within minutes. If you see
little bubbles it's >working. Give most parts a day and they come out with
no rust. >This process turns the rust into a black substance that you can
>wash off with a stainless steel wire brush and a scrub pad. Wear >gloves
while cleaning or the black stuff will stain you fingers. The >rustier the
part the longer it needs to soak.
> This process will remove paint and all the rust and will not damage >the
good metal. It is much gentler on the metal then a wire brush >on a drill
and is a lot easier. When the solution gets dirty dump it >on your lawn.
> The grass likes the iron and gets real green.
> The rust removal system works great. A note of caution. The >bubbles
> coming off the positive and negative electrodes in the solution are
> Oxygen and Hydrogen. They aren't poisonous to breath but the >Hydrogen gas
is extremely flammable. Do this process in a well >ventilated area.
> Air it out before you do any gas torch or arc welding operations.
> One problem is that once you clean the part with water and a >scrub brush
you will need to dry it and be ready to paint it with a >primer or it will
flash rust. Remember, you can leave it in the >solution till you're ready to
clean it. This process will not hurt good >metal only rust. I took a rusty
rim for three days and it looks new.  >Jerry Mannix White 56 -
>
> Question: How does this solution affect other materials like rubber >
bushings or plastic parts. In other words, do steel parts to be
> de-rusted have to be completely stripped down? And one last >question,
what about embrittlement of parts like springs? Is this >method safe to use
on suspension parts etc?

> It doesn't.  This is basically (really there is a lot of other stuff
> going on also, as it is a double compound replacement reaction) >an
electro-chemical process that changes the ferric oxide (Fe2O3, >scaly red
rust,) to ferrous oxide (FeO, black hard rust).  The >solution sodium
carbonate and water is a buffered basic solution >with a PH of  10.  So, if
an alkali (basic) mixture won't hurt it, it is >ok.  It does not affect the
strength or hardness of the steel or iron, >beyond that already done by the
original rust.  You are simply >coating the part.
> Anodizing aluminum is a similar process although it is done >through a
chemically different process.  Aluminum or any other >reactive metal in this
bath, will pit extremely fast. Jim Davis
> You can use any steel but stainless steel lasts longer. Normal steel >
like a cookie sheet will last about a month and corrode away. Get >an old
stainless kitchen pot at a yard sale.  Don't use baking soda, >WASHING SODA
makes a much better solution. Baking soda >works but will slow the process
and you need to keep adding it to >the solution you have. The purpose of the
washing soda is to >create an electrolyte solution, washing soda is a better
conductor. >It also costs less then baking soda.
> You won't hurt anything by using baking soda but you may have a higher
> electric bill due to the fact it will take longer to de-rust each part.
> With either solution you use you have to change it or add more >soda every
few weeks to keep it working at top efficiency.
>
> I found this technique (sodium carbonate and electrolytic >reduction) on
the antique stationary engine mailing list.  I was >intrigued, but also
distrustful.  Surely it was corrosive, hazardous, >or something similar.
> All the chemical derusting techniques I had seen involved acids >and
corrosion of good metal.  The stories thrown around >suggested that this was
not so with the washing soda method.
> I searched and found that museum conservators with irreplaceable >ferrous
artifacts prefer this method precisely BECAUSE it does >not allow any
corrosion of intact metal.  If done with Sodium >Hydroxide (lye) instead of
with Sodium carbonate, it's actually >capable of converting iron oxide
> back into metallic iron.  (NOTE:  I DO NOT
> RECOMMEND USING LYE FOR THIS PURPOSE.  Its >advantage over washing soda is
largely theoretical and it is vastly >more DANGEROUS) For that matter, the
process does not >remove the corrosion products; they are instead
electrolytically >reduced from rust to black magnetite, but they stay
> right there on the metal until you rub them off with a stiff >toothbrush
or something similar.
>
> The solution will have no effect on rubber, but may roughen the surfaces
> of some plastics.
> Remember that the reaction is done in a reducing bath with an alkaline
> electrolyte.  Hydrogen embrittlement is
> from exposure to acids.  (free hydrogen radicals attacking metal)
> Admittedly, the electrochemistry alters the case somewhat, but
> emperically I'd be willing to argue against measurable ion migration out
> of the metal itself over the amount of time that derusting is performed.
> The areas to be derusted need to be free of anything that would inhibit
> the solution making intimate contact with the
> metal itself.  Free flow of electrolyte past the surfaces is important
> in maintaining a constant field strength and solution concentration over
> the surface being treated.  Greasy metal is a bad idea. So is a
> significant covering by anything else, although I've seen it do a fine
> job in removing paint after immersion for a week or so.
> One other huge win of this process over any other rust removal procedure
> I've found is that it reverses the swelling that binds rusty parts
> together. The problem is caused by the simple fact is that rust is
> bigger than the iron from which it came.  Accordingly, a rusty bolt
> swells in the rusty hole in which it is threaded and no longer unscrews
easily.
> The electrolytic reduction process turns the rust into magnetite, which is
both mechanically weaker and smaller than rust.  Usually you can unscrew
parts that have rusted together if they're carefully treated in the bath for
a while.  My test case for this was a pair of
> otherwise-good 140 HP exhaust manifolds which had bolts screwed (and
rusted) into the drilled-out stud holes.  After cooking for about a week the
bolts unscrewed with moderate effort.
Rad Davis
> Jim Davis wrote: Rad got me started with this a couple years ago.  It
works as  advertised.  Be patient a really rusty part will take 24 to 30
hours to  completely harden. For those young ones who have never hear of
washing  soda; it is sodium carbonate.  It that chemical we use in swimming
pools  to raise the PH. Jim Davis"
>
>