I have this old set of casters I'm trying to save. Steel everything, quite
rusted. They still turn but sound like a sack of cats. These don't disassemble
and the replacement ones have plastic wheels. Yuck. So I'm trying to get the
rust off. These are stem casters, 7/16"x1-9/16" stem, 2" wheels. Yesterday I
suspended one by the stem into an electrolytic derusting solution and gave it
a whirl. The caster housing derusted beautifully but there is apparently too
little electrical contact with the wheel to have any effect.
How can I EDR the wheel? I thought of soft-soldering a wire to the rim of
the wheel and suspending it by the wire (with just the top of the wheel
out of the solution). Is there any better way?
GWE -- rookie EDR'er
Don't have one, really good idea though.
This one I thought of. It's a great idea too. I don't have any wire that
isn't galvanized, though. I actually did solder on a stranded copper wire
and it's cooking right now. I'm normally lousy at soldering anything except
electronic components but I just kissed the face of the wheel on the disk
sander to get a clean spot and my ancient roll of rosin core solder stuck
to it fine.
The bubbling action I'm getting isn't very aggressive, although the test run
yesterday realized good results in about six hours. I don't have a DC ammeter.
I do have an AC ammeter. I'm planning to cobble up a setup using a variac and
a rectifier bridge and to put the AC ammeter in series between the variac and
the bridge. My brain is too far removed from electronics to be able to suss
out the relationship between AC current upstream of a rectifier, and DC
current downstream. Anyone know?
I used an old plastic bucket, Arm & Hammer washing soda from Safeway (about
1/4 cup in a gallon), and a piece of old square steel tubing for the anode. I
sanded a spot clean on the outside corner of the square tube and drilled a
hole near the end, and threaded some stranded copper wire (stripped, of course)
through and twisted it tightly. I set the tube on a piece of PVC so the top
of the steel was just above the surface of the liquid, with the copper wire
(insulated, of course) hanging up over the top of the bucket. I attached another
copper wire to the steel caster to be derusted. I drilled a small hole in a flat
stick and ran the wire from the caster through the small hole, and put a clamp
on the upper side, then layed the stick over the bucket and arranged it so the
caster hung inside the steel anode without touching it, connected a small
automotive battery charger (red to anode, black to part, connection is critical)
and plugged it in. Six hours later I unplugged the charger, removed the part
(wire still attached) and ran very hot water over it while hitting it lightly
with a maroon 3M pad. Lots of black came off, and underneath - voila - no rust.
Except on the caster as my previous post indicated. Now I'm repeating the
test this time with the wire attached to the wheel instead of the caster stem.
For a transformer with a winding ratio of N1 ( pri ) and N2 ( secondary
), Voltage on the secondary ( E2 )
Voltage on the Primary ( E 1 )
Current on secondary ( I 2 )
Current on Primary ( I 1 )
E1/E2 = N1/N2 = I2 / I1 , E1 * C1 = E2 * I2
The first equation is the volttage steps up in the same ratio as the
The current steps up in the inverse ratio of the windings.
The second equation is just power in equal power out ( neglecting
slight losses )
I forgot to mention that there is a imaginary current on the primary
side which is the magnetizing current. You can measure it by
disconnecting the secondary from the load and measuring the primary
current.. So don't try to measure the primary current and calculate
the secondary current.
Grant, I have a handful of el-cheapo alligator clips that came out of
a junk box. They work well. Because of the polarity, they will not
be damaged by submergence in the solution.
You may need to file away the rust in order to make good electrical
Electrolytic derusting works very well on cast iron, less well on
I don't think you will be able to get inside a hole (the wheel) with
this process. If both the wheel and the axle ARE connected to the same
side of the power source, then the charges will be the same and no
electrolytic action will occur.
Grant Erw> I have this old set of casters I'm trying to save. Steel everything, quite
I'm done with the casters now. The last 3 I did all at the same time -- wired
a steel wire around the rim of the wheel, then up and around the stem, twisted
tightly so it made connection to both the wheel and the caster body. They
didn't turn out perfect, but 90% of the rust came off. I worked some grease
down onto the axle with a sailmaker's needle and now they turn smoothly so I
believe the rust down there was dealt with. YMMV. - GWE
Pete & sheri wrote:
By the way, there is another EDR method rarely mentioned on this NG, not
mentioned in any of the normal derusting papers. Orrin, this one may
interest you. The method is passive rather than active -- in other words,
you don't have to add energy in the form of electricity. No more wires.
Simple. Make up some strong hot lye, dissolve in a chunk of zinc, and
drop in the rusty part. The zinc reduces the oxidized iron.
There are Web pages about this -- google on lye and zinc and you'll see 'em.
If you don't think you have any zinc, you're likely wrong. Many inexpensive
cast metal items are made mostly of zinc. Car door handles, mirror bases,
lamp bases, stuff like that. Try a coarse file on it, if it peels away like
butter that's the stuff. It's been posted on this NG that lye will bubble on
zinc (pot metal) but not on aluminum.
There is also molasses as a passive bath. You buy the molasses pellet
feed that is sold for horses, mix it into water to make a slurry and
toss the parts in. Let them sit 1- whatever (depends on how bad the rust
is) days and when you take them out wash them clean.
Grant, thank you for reminding me of that method. I'd heard of it,
recently, but the recipe I read called for heating a solution of lye.
It sounds a bit hazardous to me.
Indeed, most of us probably have zinc all around us and we don't
realize it. Die-cast pot-metal items are almost everywhere we look,
especially in the kitchen and bathroom.