Using a welder for electroplating

You are 100% right. There is enough resistance to make the voltage at terminals about 2 volts. Even the copper strip that I used warmed up considerably.

The reason why I am so interested is that I have some lead sheet leftovers that I could use as anodes.

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

You just can't get 2V across a "copper bar" - it would melt almost instantly.

Nope, my experience is all with Ohm's law. Good on electrons, bad on bogons.

If he's going by the volt meter on the welder it most likely represents the voltage across not only the copper bar, but also the welding leads.

Pete C.

Yes, plus the bar itself would be properly called a copper strip.

In any case, as I said, we became sidetracked.

I know that my welder is a constant current welder. I am not sure why we are arguing over this.

The original question was, is a constant current welder such as my

The answer from Don Foreman indicates, sensibly, that the answer is yes. I also suspected so and am now convinced that it is the case.

And yes, my welder is able to supply as little voltage as necessary, when faced with low resistance.

Sorry, this is annoying me.

You just can't get 2V across any short length of copper, of any thickness - it would melt almost instantly.

I didn't mention that I was actually processing two batches of rebar a day. The current density was much higher than ideal, but I was in a hurry.

Next time I'll buy new rebar and scrap the rusty stuff :-)

Mark Rand RTFM

replying to Grant Erwin, S G wrote: carbon crucible blocks work better, no sludge

replying to Don Foreman, S G wrote: A friend uses 1000amp 6volt rectifier but that unit costs $7500 bucks, 3 phase

replying to Andy Dingley, S G wrote: for a car body like a mustang use 6v 1000amp for 2 hours , start the solution off hot, ue carbon/graphite blocks to avoid making sludge

replying to Grant Erwin, S G wrote: carbon crucible blocks work better, no sludge

replying to Don Foreman, S G wrote: A friend uses 1000amp 6volt rectifier but that unit costs $7500 bucks, 3 phase

replying to Andy Dingley, S G wrote: for a car body like a mustang use 6v 1000amp for 2 hours , start the solution off hot, ue carbon/graphite blocks to avoid making sludge

Load vs temperature rise testing of the variable power supply I built from a 50A, 20% duty cycle arc welder transformer and a variac showed that the output current should be limited to around 20A continuous or

P = I^2 * R, where R is the copper winding resistance.

Arc welding transformers have a fairly high internal impedance to cheaply provide high no-load voltage to start the arc and current limiting when welding, especially when the electrode sticks. The tradeoff is low efficiency. This means that the voltage drops significantly as load current increases, and conversely the voltage rises if the load's current demand decreases, as when a battery nears full charge.

This voltage and current regulator is a good match to the 50A transformer: