electrolytic derusting electrodes - a new idea

I read Orrin's bit about using graphite electrodes for electrolytic derusting. I saw some cheap on ebay and picked up some, maybe $10. The first ones arrived smashed up, the second ones showed up intact. They're about 8" long, maybe

1/2x1" rectangular bar (very roughly). They look fragile. As I said, they were over $5 apiece. They will probably work fine, although I often need an electrode that is longer than that.

Today I was rooting around industrial South Seattle looking for a used but usable welding ground clamp and I noticed these long perfectly round things that looked just like graphite. I picked one up -- it's 12" long, 3/8" diameter, looks pretty strong, looks real conductive. It's a scarfing electrode, first unclad one I've seen, and it must be made of some sintered carbon. They had hundreds and hundreds available for 35¢ each. Skeptical, I bought one. I just hauled out my DVM and my pointy-sharp leads and probed in in ohmmeter mode. End to end it's 2 ohms or less (my meter isn't accurate in that range) and it appears to be just as conductive on the sides as on the ends. In short, it appears to be a real good candidate for use as an electrolytic derusting electrode!

I'll test it and report. This would be great if it works like I hope it does, it would mean electrodes that don't rust, no cruddy solution, without the huge expense and fragility of graphite.

GWE

Reply to
Grant Erwin
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Since I'm gonna be in the area in another week or so, where is that shop, and what other electro/mechano/nerd junk stores are still in business? /mark to the North

Grant Erw> I read Orrin's bit about using graphite electrodes for electrolytic

Reply to
Mark

"Grant Erwin" wrote: (clip) They had hundreds and hundreds available for

35¢ each. Skeptical, I bought one. (clip) ^^^^^^^^^^^^^^ You bought ONE? That's almost like a guarantee that when you go back they will be all gone, or the price will have gone way up. I would have made an offer on all of them, and taken a chance. (That's why my garage is full to overflowing with bargains like this.)
Reply to
Leo Lichtman

It isn't what you're thinking, not a junk store, although they do carry some used stuff. Anyway, it's Pacific Industrial Supply Co. on 4th South in Seattle, a couple of blocks north of Spokane Street. Wear ear plugs, their PA is LOUD.

Pacific Industrial Supply Co.

2960 4th South Seattle, WA 98134 206-682-2100

They are *not* going to sell out of scarfing electrodes. Plain carbon arc gouging electrodes are featured in many catalogs including Tweco's. That's the whole point, if this concept proves out, anyone can get great EDR electrodes easily and very cheaply.

GWE

Reply to
Grant Erwin

Graphite electrodes y'say? Heck, gouging rods work great, long as you don't ask too much of them. (Electrolysis of salt solution (say to make a strong oxidizer like sodium chlorate) easily wears down any graphite of course.)

You can remove the cladding by anodizing (heh) it in a salt solution until the metal dissappears (leaving copper oxide floating in solution), then it's free to use for whatever.

Industrial graphite works good too, I got three 1 1/2" square 18" long bars from a surplus dealer on e-Bay for a total $30 with shipping. Came from around your area, as a matter of fact.

Tim

Reply to
Tim Williams

Well done! I've been looking for graphite block electrodes on the right side of the pond without much (any) success, but I can get 13mm...1/2" gouging electrodes at £35/100. I can live with that price for something that works.

I'll be waiting for the test report.

Thanks for the idea.

Mark Rand RTFM

Reply to
Mark Rand

If you ever get around an electric arc furnace, ask for some electrodes that have gotten too short to use. (There's a foundry near Coeur d' Alene that uses an electric arc furnace.) Or, if you know anyone who works at an aluminum smelter, ask them to pick up some carbon for you. The pot lines use carbon electrodes.

The large dry-cell batteries used in crank telephones and Hot Shot batteries have large (about 1-inch diameter) carbon electrodes in them.

Another source of carbon is from decomissioned graphite-shielded or graphite-moderated nuclear reactors. Don't laugh. I once had hundreds of pounds of it; gave most of it away, though. (Yes, I did have it checked for radioactive contamination.)

There's one bit of warning about using graphite or carbon, however. Some kinds of binder appears to be affected by either the solution or the electric potential.

I had a very embarrasing thing happen to me, once. I very generously (so I thought) gave away--to a whole crowd of fellows--graphite plates that I'd sawed (sawn?) from bigger blocks. Later, I used one of them in my electrolytic vat. Much to my embarrassment, it disappeared overnight. It turned to mush and fell to the bottom of the tank. Apparently, the binder dissolved.

On the other hand, I've had some graphite electrodes last for over a year of continuous duty in my electrolytic de-rusting setup.

I've gotten some good graphite deals on eBay. One needs to be selective, however.

Orrin

Reply to
Orrin Iseminger

Reply to
David Billington

What am I missing here? I use FREE electrodes that will last nearly forever unless the polarity gets accidentally reversed. I find them along the road disguised as stainless wheel covers. The current one is from a Buick. I like it better than the Cadillac one it replaces.

George Willer

Reply to
George Willer

Does your solution slowly turn yellow? That's hexavalent chromium, and it's DEADLY POISON. That's why it's strongly suggested not to use stainless electrodes.

GWE

Reply to
Grant Erwin

No, it doesn't turn yellow... should it? Just to be safe I'll refrain from ingesting the glop from the tank. I have noticed the stainless gaining a tinge from the paint color of the part being de-rusted. It wipes right off so it may not be electrically deposited, but simple settling.

George Willer

Reply to
George Willer

That would mean the electrode is reacting, I'm assuing it isn't supposed to...

Cr6+ can be absorbed through the skin as well, so wear gloves around it. (Cr3+ is almost as harmless as table salt, in contrast.)

Cr6+ is easily reduced, if you have some ferrous sulfate or sodium bisulfite (or any sulf_ite_ for that matter, including SO2 gas) on hand, that'll reduce it no problem.

Paint is usually an insulator so that sounds about right.

Tim

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Reply to
Tim Williams

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