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I often use electrolysis to remove rust and other junk off of steel parts. My general setup is:

  • Electrolyte: Sodium bicarbonate + distilled water.
  • Anode: Plain carbon steel
  • Cathode: Carbon steel, iron oxides, and "junk" (e.g. stubborn bits of paint, small amounts of oils / greases, etc.)
  • Power: 9-24V, 2-10A

Every once in a while, the "junk" on a part (cathode) leads to the formation of foam on the surface of the solution. Of course having a well-cleaned part reduces or prevents this but ... sometimes these things happen.

The problem is: The foam is mostly hydrogen and oxygen gasses, and it's explosive (or flammable or whatever, but it goes boom). And it's near wiring that could spark. So I'd really like to not have any foam.

For example (this is mild compared to some of the situations I've seen) (video of me igniting it):

enter image description here

The pH of the solution in that particular example is ~9.3, if it's relevant.

So my question is: Is there something I can add to the solution that will remove the foam (or prevent it from forming) but that also won't interfere with the reactions at the cathode? Ideally, something that also won't leave me with a hazmat to dispose of, either (NY, USA).

I'm not really sure what keywords to use in searching, so even some terminology tips would be helpful. (Update: "Antifoaming agents")

Update: Simethicone emulsions are the current best contender; discussion in comments below; will post if I can get consistent good results.

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    $\begingroup$ Might try over the counter “anti-gas” stuff sold in drug stores. It is intended for human stomach use, so no disposal issue. If it works to suppress the bubbles, then case closed. $\endgroup$
    – Ed V
    Commented Dec 15, 2021 at 19:38
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    $\begingroup$ @EdV Good idea. Simethicone, iirc. Will have to be wary of additives for testing but if it works the lab grade stuff is a little pricey, but not prohibitively expensive (especially if it doesn't take much). $\endgroup$
    – Jason C
    Commented Dec 15, 2021 at 19:41
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    $\begingroup$ @EdV Simethicone acquired. Internet says it's very insoluble in water but it's also slightly less dense so maybe it'll float on top and do its thing. Fingers crossed. Got softgels; the drinkable stuff is mixed with aluminum and magnesium hydroxides and also has less of the stuff in it. $\endgroup$
    – Jason C
    Commented Dec 15, 2021 at 20:10
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    $\begingroup$ Alternate Plan B, if the simethicone fails: a quick short spritz from a can of engine starting diethyl ether (aka engine starter fluid). Reference: early on in Fear and Loathing in Las Vegas by Hunter Stockton Thompson. $\endgroup$
    – Ed V
    Commented Dec 15, 2021 at 20:51
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    $\begingroup$ Perhaps just provide a steady stream of air across the surface to an outside vent. This is what is (or was, pre-Li-ion) done where large lead-acid cells are charged, such as aboard ships and in telcos's. $\endgroup$
    – DrMoishe Pippik
    Commented Dec 15, 2021 at 21:21

1 Answer 1

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In the beverage industry (think sugar-based fizzy drinks and beer) foaming has to be reduced prior sealing the cans, this is done by ultrasound. The cans and bottles underpass an airborne ultrasound probe which pointing downward.

enter image description here

(Screen photo from this youtube video, edited.)

Since there is no contact between the probe and the bottle, nor immersion in the liquid, it seems likely you may keep the electrodes attached. These probes come both in larger (example corporate documentation) as well as mobile and hand held size (example video).

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    $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$
    – andselisk ♦
    Commented Jan 20, 2022 at 17:32

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