electrolytic derusting electrode material

magneticanomaly · Jul 16, 2021

I have used an expendable steel positive electrode for this process, but it gets smaller and adds to the mess. Stailess might be an option but might create dangerous hexavalent chrome in the bath.

Graphite or carbon seems ideal. But brittle, so maybe hard to handle and hard to make a good connection to. Any thoughts about carbon fiber cloth? Seems about similarcost as graphite plates for same area

thermite · Jul 16, 2021

magneticanomaly said:
I have used an expendable steel positive electrode for this process, but it gets smaller and adds to the mess. Stailess might be an option but might create dangerous hexavalent chrome in the bath.

Graphite or carbon seems ideal. But brittle, so maybe hard to handle and hard to make a good connection to. Any thoughts about carbon fiber cloth? Seems about similarcost as graphite plates for same area

I use the round rods made for the old MacBeth carbon arc lamps used in theatres or as we used in the printing industry to "burn" plates before Xenon got cheap.

About a dollar each in boxes of fifty.

Bigger ones are still around, too - surplused off Military searchlights. Run short of cheap ones, just check yer welding supply house for gouging carbons.

Easy to clamped a wire to them so one can position several - depending on the size and shape of the part - and/or move them about - hung off a powered suspension.

That so as to reduce electrode shadow effect.

As good as plate or fabric? Probably not. But they were MEANT to have a clamp, they survive that, and are easy to use,

ratbldr427 · Jul 16, 2021

If you know any body that uses vane air pumps such as Becker or Gast,have them save the old vanes when they change them. The 5/10 /hp models have 4/6 carbon vanes various lengths. We are in the printing business and have 30 or so pumps to maintain so a good supply if I ever needed them.

metalmagpie · Jul 16, 2021

I use lead sheet, the kind roofers use. I wash them after every use and don't store them in the bath long term. They work fine, no dropoff in current.

metalmagpie

magneticanomaly · Jul 17, 2021

Thanks for the suggestions! It occurs to me that I have some old battery carbons that i will try. I wanted something longer, so the connection would be well above bath level to save fiddling with corroding connections, but free is hard to argue with.

mattthemuppet · Jul 17, 2021

graphite rods (EDM?) are what I've seen recommended. Never got round to getting some myself, still using the 2 pieces of bent 3/8" rebar that I started with

thermite · Jul 17, 2021

magneticanomaly said:
Thanks for the suggestions! It occurs to me that I have some old battery carbons that i will try. I wanted something longer, so the connection would be well above bath level to save fiddling with corroding connections, but free is hard to argue with.

The Arc-lamp rods are over a foot long and fit relatively common clamps for round goods. (C)PVC pipe makes a saner frame than wood.

I don't do enough of it to much care about corrosion, sludge, nor smut, but did NOT want other METALS involved "much" - be they Chrome, Nickel, nor even Copper, Tin, or Zinc.

Lead? Pass. Avoidable enough in general I don't much care to even look-up the chemistry.

Scottl · Jul 17, 2021

magneticanomaly said:
Thanks for the suggestions! It occurs to me that I have some old battery carbons that i will try. I wanted something longer, so the connection would be well above bath level to save fiddling with corroding connections, but free is hard to argue with.

Do as metalmagpie suggested and use lead. Lead roof flashing in 6 inch width can be cut to whatever length is needed.

Mark Rand · Jul 17, 2021

Just a couple of points:-

The green colour you get when using a stainless steel anode is indicative of Chromium III ions. Chromium VI ions would show a brown/orange colour.
If you use washing soda as the electrolyte with lead anodes, you'll get a white precipitate at the bottom of the tank. This is lead carbonate or "white lead". It seems to build up fairly slowly, but it does build up.

Both lead and stainless steel last far longer than mild steel. My only experience with carbon/graphite, so far, showed that arc gouging electrodes turn to mush

. I've got a 2"x2"x3" block of EDM electrode stock, but need to slice it into sheets before I can use it. At the moment, I don't need any electrolytic derusting so it's sitting on a shelf.

john.k · Jul 17, 2021

Rule #1 of hobby experimenting......Dont turn your yard into a toxic site......when you sell ,it could cost you plenty....Iron oxide is OK.

reggie_obe · Jul 17, 2021

mattthemuppet said:
graphite rods (EDM?) are what I've seen recommended. Never got round to getting some myself, still using the 2 pieces of bent 3/8" rebar that I started with

Old EDM graphite can be had for almost nothing, drills and saws with ordinary tools. A good connection is wire run through a hole and twisted.

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