I've heard of guys using MIG machines (CV) to do electrolytic derusting. In that
process, the variables you have are strength of solution (i.e. 1/4 cup washing
soda or the whole box?) also distance to the electrodes and to some extent
electrode topology. In my most-used setup, I use a square 5-gallon bucket that
once contained laundry detergent (itself mostly cut with washing soda) and two
railroad track ties with 10 ga. wires soldered to the track ties. The track ties
lean in the bucket against the sides, leaving a nice volume for workpieces,
which I suspend via a wire/clamp through a stick over the top of the bucket. The
problem with this setup is that it's a real hassle when your current isn't
enough, or is too much. All I can do with a buzzbox car battery charger is
toggle 6V/12V. With a MIG welder, however, I can crank the voltage wherever it
needs to be to get the desired level of bubbling, and after the electrodes "load
up" I can crank it up a little more to overcome the resistance.
That's a MIG welder, though. A CC source would be really great as long as you
can really control the current. Most of the time I'm shooting for 3-15 amps (I'm
sure what you really want is some value of amps per unit workpiece area, don't
know what that is) and if you can hit that easily and controllably with a CC
welder, why sure it will work.
I don't see you have much to lose. I suggest you give it a try and report back.
Andy, I will check my welder for what the minimum amperage of its
output could be. My welding machine has digitally settable output
current, although I do not know how low it goes. My guess is that I
could get under 20 amps, maybe a lot less (like 10 amps).
The voltage on this constant current welder is automaticaly adjusted
to provide desired current.
Assuming that it is the case, do you still have objections to this
The _voltage_ will be too high. You don't have any way of reducing this
(for any welder I've seen) down to the low voltages required.
Besides which, electroplating is a foul process. If you're into the
region where you need kW of power, then it's a serious chemical waste
handling problem. For "backyard" scale work you can just lash something
up from the junk pile.
Here's a piece of electroformed copper (the underlying skeleton is
plastic) about 12" across - work by a friend of mine. Nothing more
obscure electrically than scrap-box transformers.
You misunderstand the concept of constant current welders, such as my
Hobart Cyber TIG welding machine.
The constant current welder adjusts the voltage, up to a certain
amount, and down to almost zero, to produce desired current.
If I short the leads of the welding machine, the voltage drops to
Similarly, if I was derusting and resistance of the setup was low, the
voltage would drop to a very low value, so that the produced current
does not exceed the current that I dialed on the welder's control.
Right. Right now I am mainly interested in derusting, using steel
electrodes, which is environmentally safe.
Plating wants a voltage of around 6-7V, with good control of current.
This isn't a "constant current" source, because if it does vary (owing
to workpiece conditions changing) then it's better if the source behaves
as a constant voltage source, once set. Current needs good manual
control though and is a crucial adjustment for plating.
Some processes want higher voltages: 12V for hard chrome, 16V+ for
anodising and some quite high voltages for anodising titanium.
I've also not seen a welder that went down to this 6V level.
I'm pretty certain that it _is_ zero. The welder will detect this as a
specific case and go into a "shutdown" condition.
We live in a world full of cheap scrap electronics. I just wouldn't use
a welder for this, when I have any number of small compact 5V and 12V
high-current PSUs just looking for new homes.
Car battery charger (old non-auto one). You only need maybe 5A tops at
12V for anything that fits in a dustbin. I've done boat hulls where I
used an old computer PSU and about 60A.
Nope. It continues to happily produce current, as evidenced by the
DC ammeter on the welder. I tried this, a dead short as well as a
short with a copper bar that had about 2 volts or so of voltage across
This is real, my welder is a constant current source that does produce
required current and drops voltage to where is has to be for that.
But why would i buy anything else if my welder can do what I want.
You can't have "a copper bar" with "about 2V across it". The power
required to maintain such a voltage would be enormous.
There are no true "constant current" sources, outside of Norton and
Thevenin - when you get to the limits, something has to give.
That's more like "two yards of thin cable" rather than "a copper bar".
2m of 10mm^2 cable, and copper has a resistivity of 2e-8/m is a
resistance of about 4m ohms With 2V across it is a power of 1kW, which
is certainly practical for a welder.
You most certainly can, it's essentially a current shunt. With a welder
happily pumping 200A+ through the bar, you will develop a voltage across
it based on it's resistance.
You've clearly never had any experience with a quality TIG welder
Of course you will. And for 200A current, that's about 8kW of power and
a voltage of 40mV (for a nominal "copper bar" shorting link of
0.0002ohms). To develop 2V across this sort of resistance needs 10kA,
not 200A - just how powerful a welder are we talking about here?.
You just can't get 2V across a "copper bar" - it would melt almost
Nope, my experience is all with Ohm's law.
Good on electrons, bad on bogons.
Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here.
All logos and trade names are the property of their respective owners.