Thread: Electrolysis solution longevity

It depends how clean it is. I use carbon anodes which keeps the electrolyte cleaner than use ferrous anodes so I can keep and re-use mine mine for years but I also value my space so there's no way I'd be keeping 100L of it. If you have the space then no worries.

YEARS!!!! Holy heck!!!
I'm using two stainless rods for anodes and scrub them between sessions, outside of the solution, and if I was really tight I'd pour out the top part of the clean solution and top it up if I was doing this regularly.
I've got the space I guess...the esky isn't used and takes up room by itself, so why not fill it up
Thanks B. Great answer

SS is not the best material to use as an anode as it contains Cr and may make the electrolyte toxic. This then become as problem for disposal. I need to do a small scale experiment to confirm this. Carbon electrodes rarely have to be scrubbed and the resulting electrolyte is non-toxic.

to that, but I rarely do these rust removal runs. Very good to know otherwise.
I scrub the anodes between each session just for the hell of it.
Disposal = emptying of each deprived solution...at the point of efficient removal.

I think that Bob is hinting that if the stainless anodes contain enough Cr, the solution could become toxic partway through a de-rusting session

Originally Posted by ian

I think that Bob is hinting that if the stainless anodes contain enough Cr, the solution could become toxic partway through a de-rusting session

Thanks for clarifying Ian. Yes the Cr in the SS will dissolve into the electrolyte which means the solutions should not be disposed of down drains or dumped onto the ground if there is a chance of it finding it's way into water ways. Even in really dilute form, some Cr solutions are highly toxic to aquatic organisms. It's also not just the solutions. Because gas is produced by electrolysis the breaking bubbles will create lots of tiny aerosols/droplets which means if done inside a shed the air may become toxic as will all the surfaces. Risk is lowered by using ventilation and reduced usage however this does not take into account individual sensitivities to Cr.

Like I said WIGRTI I will do an experiment to determine the amount of Cr liberated from SS into an electrolysis solution and compare that to the OHS standards for Cr workplaces etc.

Originally Posted by BobL

Yes the Cr in the SS will dissolve into the electrolyte which means the solutions should not be disposed of down drains or dumped onto the ground if there is a chance of it finding it's way into water ways. Even in really dilute form, some Cr solutions are highly toxic to aquatic organisms. It's also not just the solutions. Because gas is produced by electrolysis the breaking bubbles will create lots of tiny aerosols/droplets which means if done inside a shed the air may become toxic as will all the surfaces. Risk is lowered by using ventilation and reduced usage however this does not take into account individual sensitivities to Cr.

Like I said WIGRTI I will do an experiment to determine the amount of Cr liberated from SS into an electrolysis solution and compare that to the OHS standards for Cr workplaces etc.

perhaps waiting for you to have the time to do an experiment to determine toxicity is not as straight forward as just outright suggesting that using stainless electrodes is a really, really bad idea.

Sadly, my heavy metal expert passed away 8 years ago.

Originally Posted by ian

Sadly, my heavy metal expert passed away 8 years ago.

but a quick inquiry of Dr Google found these gems:


Many people using the electrolysis method for rust reduction swear by stainless steel, stating (incorrectly) that it's not consumed, stays clean and seems safe.

Stainless steel is indeed consumed when used in the electrolysis process, although slowly. The main problem with using it is the hazardous waste it produces. Stainless steel contains chromium. The electrodes, and thus the chromium is consumed, and you end up with poisonous chromates in your electrolyte. Dumping these on the ground or down the drain is illegal. The compounds can cause severe skin problems and ultimately, cancer. Hexavalent chromate is poisonous. These compounds are not excused from hazardous waste regulations where household wastes are.

These compounds are bad enough that government regulations mandate "elimination of hexavalent chromate by 2007 for corrosion protection."

Does your electrolyte turn yellow? That's a sign of chromates.

If you have been using stainless steel for the anodes (positive electrodes), wear rubber gloves when working with or near the liquids. If you need to dispose of it, allow it to evaporate into powders and dispose of the powders in sealed containers during your local "hazardous waste clean-up days".

Best bet - don't use stainless steel no matter how tempting it is.



and

Chromium is an element. It is forever. There are all sorts of LAWS concerning how you must handle waste containing it. Reducing Cr(VI) to Cr(III) does reduce the hazard, but does not eliminate it. You can not legally dump caustic solutions down the drain in the USA, which means using NaOH is a really bad idea. It is against the law.

Chromium is fairly easy to trace through a sewer system; that means if you dump it, be prepared to spend some time in jail.

Thanks Ian, I've posted the same info as you posted above in these forums several times in the last decade.
The last time I think may have been when the metal work forums were part of WWF.

I still want to do the experiment even if its just for my curiosity. I will do the experiment on a very small scale and can do it safely as I have a suitable fume hood in my shed and can also dispose of any possible Cr waste though my uni contacts. What I suspect happens is folks use car battery chargers for electrolysis. The resulting 12V is completely unnecessary and results in significant anode erosion and the production of large amounts of gasses (ie aerosols) and Cr contaminated electrolytes. What I want to investigate is if a suitable (ie lower) V is used with SS anodes whether this effect can be minimised or eliminated.

The chemistry will be the same whether you use a 12V car battery charger or a computer power supply or another source of electrons.
The speed of the reaction and hence rust conversion / removal should vary with the input current. As might the formation of aerosols.

If you do do the experiment are you set up to
1. measure the Cr content of various stainless steels -- and how would a "typical" user know which stainless steel they had if the source is an old piece of cutlery or a bit of rod from a recyclers?

2. measure the concentration of Cr in the solution?

3. measure the "loose" or free Cr on the surface of the anode when it is extracted from the solution for "cleaning"


I can see where the experiment might satisfy your curiosity, BUT in terms of educating forum members and visitors, I think the responsible approach is to "just say no" to stainless electrodes.


I'm sure that you are aware that if you're a middle aged male, the ingestion of a small amount of lead is not all that harmful, but if you're a child or a fertile female ingesting the same amount of lead (by body weight) can be very harmful.

I don't know, but the same is possibly true for Chromium.

Ian, I agree - the experiment is for my own curiosity only. I have a medical condition called Sarcoidosis and exposure to heavy metals is possibly a cause of this so I interested to know if previous exposures may have contributed to this.

FWIW I have performed a number of Cr investigations going back as far as my Masters when I measured Cr in waste engine oil using Neutron Activation Analysis. Then in the USA I spent 2.5 years as a post doctoral Fellow measuring amongst other things, ultra trace amounts of Cr in meteorite grains by Isotope Dilution Mass Spectrometry so I am very familiar with the chemistry side of Cr.

RE: Kids and pregnancy.
That's what I meant in part by
"Risk is lowered by using ventilation and reduced usage however this does not take into account individual sensitivities to Cr."

ventilation might reduce risk for the person doing the electrolysis, but I'd also worry about material tracked inside on the person's clothing or footwear.

Just a thought, is pure dc i.e. from battery or regulated power supply better than that from an unfiltered battery charger ?

Originally Posted by dinosour

Just a thought, is pure dc i.e. from battery or regulated power supply better than that from an unfiltered battery charger ?

Not really - the problem with using any 12V supply is the resulting current can be unnecessarily high even if dilute electrolyte is used. The higher currents produce large volumes of foam which traps hydrogen and oxygen in the bubbles which besides being dangerous can lead to hydrogen embrittlement of parts . The higher currents builds up sludge on steel anodes meaning they need to be regularly cleaned.

Only a few V is required to perform adequately electrolysis and its better if it goes slowly so the gasses get time to dissipate - suggest you do it outside if you do not have adequate ventilation. If you are budget conscious then something like an old PC power supply can be used and use either the 5 or 3.3V outputs which have a max currents of 20A+ so this is not an issue for most electrolysis. There are a zillion "How tos" on the web showing how to set one up safely.

If you have a variable V supply you can optimise the current by adjusting the V but if you don't have a variable V supply then you can vary the current by altering the concentration of the electrolyte/solution. Before I had a variable V PS I used the 3.3V output of a PC power supply and a dilute electolyte, then I mixed in small amounts of concentrated electrolyte slowly till the current reached 4 -> 5 A.