Using NaOH for electrolyte

S

ShawnE

Member
Hi All,

Has anybody tried using lye as an electrolyte in their e-tank. I was thinking that instead of the two step process of 1) soaking in a hot lye bath, 2) electrolysis using calcium carbonate, that one could combine the two steps by using a lye solution in the e-tank. I know that the lye works better at a higher temperature. When I push a fair amount of power into my e-tank (350W, 23V@15A) I get a good amount of heating (180F after 6 Hrs or so). I would also think that the hydrogen bubbling off of the part would agitate somewhat helping to remove the crud and exposing the base metal below. Similar to how an ultrasonic tank works.

I thought that I would see if anybody has done this and what their experiences were before I tried the experiment.

I do understand that you have to be careful with lye and skin contact, so I'll take precautions and am not worried about that.
 
People have, but not in the way you're talking about. More like 1 Tbl. per gallon, not the 1 lb. per 5 gallons for a lye tank. It is in fact used in industrial electrolytic applications, at 2-5% solution, and where its higher pH is found to help with anode performance. Electro using sodium carbonate for the electrolyte seems to me to work just fine, taking off crud and rust in a more than reasonable amount of time with very little trouble, and crud much faster than lye alone. I can see no reason to make it more complicated or potentially dangerous.
 
Ok, so you have no direct experience then. Unless anyone else here has direct experience then I'll try. My motto in my R&D work has always been "One good test is worth a thousand expert opinions". For myself I don't think that there is much extra danger, I've worked with much worse. HF (hydrogen fluoride) for example. As to the concentration, I'll titrate to find the optimal ratio. I expect that I'll start at a ph of 13 and/or a cell resistance of 1 - 2 ohms or so to start and then work up from there. Thanks, it may work for me or it may not, I'll see.

The hot lye bath followed by a sodium carbonate electrolyte e-tank worked ok for me, my motivation was to reduce my work load. I guess that is the engineer in me to do upfront R&D to reduce per unit cost (in this case cost is in Hrs). Besides R&D is fun, that's why I do it for a living.

Oooops... Meant sodium carbonate, not calcium carbonate in the first post.
 
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I have done some reading about the industrial electrolytic applications with its higher pH. But due to the amount of crud coming off the pieces and getting the water all dirty and needed to be changed all the time. Setting up my new E-tank in the spring with Graphite in the spring, so less cleaning. I thought it best to have my big lye tank (40 gal.), so I can clean all the crud off there and the rust in my
E-tank. Not all pieces have rust and need the E-tank, but every one goes in the lye tank. My lye tank will get dumped 1 - 2 times a year, I do add some water and lye at times.

So I went to an auction on Saturday and came home with 21 pieces, of which 4 did not go in the tank last night, and only 5 will need to go in my E-tank. Less cost on the electric bill.

But would be interested in your test.
 
Jeffery,

After reading a few papers on the subject, I think that I have an initial process experiment to try. I was taught the the first thing in developing a process is "what does success look like". This came from Intel, which I regard as the best manufacturing company in the world. My answer to that is I want to take the worst rusty and crusty piece of iron (cookware or engine parts) and end up with clean bare metal without damaging the part.

That being said, I think that the first stage in my initial process will probably be a hot strong lye bath (with or with out electrolysis assist). Electrolysis assist in the initial lye bath will give some mechanical scrubbing due to the hydrogen bubbling, as well as helping to keep the temperature up. I think that some sort of agitation will help, but I don't want to add something like an ultrasonic transducer. Followed by some scrubbing.

The second stage will be electrolysis using lye as the electrolyte and probably a mild steel electrode. I'm thinking of mild steel mesh screening as it is cheap, readily available, and easy to cut and bend to conform to the inside of the tank.

Next a water rinse and a quick towel dry.

I think that putting the piece in a drying solution like dry IPA (isopropyl alcohol), or acetone, or dry methanol to remove all of the water would be next. Dry methanol will probably be my 1st choice as it is cheap and readily available. Just go to any race shop that is around a track that runs sprint cars. I can also do any final scrubbing while submerged in the drying solution. Acetone is probably a better technical solution as it will break polymer chains better, but it is a pain to work with for that same reason, as it dissolves many plastics too.

This should bring the part down to bare metal and inhibit the tendency to flash rust. When ready to season, I would remove it from the drying solution, give it quick wipe, then bake in an electric oven to drive off the solvent as well as getting it ready to accept the oil (Crisco probably).

Now I know that I'm probably over thinking this, and it won't scale well for the medium volume backyard type. But hey, process development is fun.

If you or anybody else can poke holes in this from a process standpoint, please chime in. I know that this isn't practical (or even safe) for most people, but this is the fun part of the hobby for me right now.
 
Like I wrote in the earlier post. But I will just list some steps and their order, that would work for me. You are on your own, but you are putting some thought into it. This is not my first rodeo, but I do tweak things.

As I deal with antiques and a lot of rusty metal, not just cast iron. Rust does not scare me away. One needs to remember that the metal is not the same as it was 100 years ago. Like everything it all starts with the ingredients. I have turned some rusty items that were sitting in an old iron pile that sat out side for years into $$.

1) Lye bath to remove all oil, grease, paint , etc., Mechanical scrubbing, maybe needed.

2) E-tank to remove rust, mechanical scrubbing, maybe needed.

3) Cold water bath with soap good rinse. Cold water keeps the flash rust at bay. My trick. Winters up here are cold and dry for the most part. So I towel dry the piece and the cold air dries it the rest. In the summer I do it inside my shop out of the sun. This works for me.

4) On some pieces that would need a drying solution, Not My Cast Iron Cookware. I would use Acetone, with an air hose to help with drying.

5) When I am down to the clean bare metal. The next step would to paint, oil, or season the piece. Every piece of bare metal gets heated to pull out moisture. Then I can paint, oil or season the piece while it is still warm. Metal is a sponge to moisture, you need to start with a clean dry piece for a long lasting finnish.

This works for me, but there are a lot of tricks in my tool bag, and timing is one of them. :icon_scratchchin:

Safety is the first part of my process.
Least cost is next.
Least amount of toxic solvents.
Do not rush. Good things take time.

This is what works for me, and I am sticking to it. :icon_thumbsup:
 
Thanks for the input. I know that I'm trying to re-invent the wheel here. But if I do, it should at least be round :-)
 
A quick update. I just got a couple of pieces, a #8 3 notch lodge and a bottom gate 2x6 cornbread pan. Both were extremely rusty. I decided to try running the lodge in an e-tank with a 2.5% NaOH electrolyte. After 3 hrs almost of the rust is gone, and it seems to be converted to magnetite (very black). There is a lot of H2 bubbling which I believe is helping to remove the rust mechanically.

The Lodge is ~1300 cm2 and I'm running ~16 amps into the cell. This is about where I wanted it to be, 10 mA/cm2. I don't have the most optimum cell at this point, the anode is an old grill grate.

Another point is that the anode had gotten pretty crusty from using sodium carbonate as an electrolyte previously. After running the NaOH cell for 3 Hrs, the anode is now fairly clean. This leads me to believe that I can run a mild steel anode without too much trouble.

About the safety of NaOH as an electrolyte, the concentration is no different than most people are using for their lye tank (1 Lb / 5 Gal).

I plan on doing more quantitative tests over the next month, but I thought I would give an update.

BTW, I'm using a current limited power supply. If you use a cheap battery charger, your mileage may vary :)

This leads me to believe that the lye tank and e-tank can be combined, at least for one off parts.
 
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So I jumped in with a 55 gal, E-tank with lye. I never thought to take a photo of the racks. They came out of an old stove top oven that I am restoring. They were rusty cast iron. So I put them in my new tank and took them out in 15 minutes, clean,done, rust is gone. :icon_thumbsup:

For me I will only put clean pieces in the E-tank. I have a small Birmingham Stove & Range wood stove that I will have to try next.

https://picasaweb.google.com/114772661409714296598/JeffreyR#6053349048203165202
 
Good to hear it. What did you use for anodes? If not graphite, how did they look? I have to get to the rem center so I can try some mild steel next
 
Great, I'm curious. BTW, what strength NaOH electrolyte are you using?

Another thought, and one I might try is to have two tanks. The 1st one would be a lye tank, but I would also run it as an e-tank also. This should help the removal of grease and carbon through the mechanical action of the H2 bubbling. The 2nd tank would be just for rusty parts only. I did notice that the rusty and greasy lodge created a "soap scum" flecked with carbon and converted rust during the 1st 15 minutes or so. I just skimmed it off. I guess that lye and fat does indeed make soap:mrgreen:
 
I will stay with my 2 tanks. Clean only in the lye tank. Rust only in the E-tank.
I am at around 4 lbs. to 55 gals. There is a lot of H2 bubbling going on. I put part of the wood stove in at 1:00, I will look at it at 2:00

Trying to play catch up today. Seasoning 6 pieces of iron, playing with the E-tank, and making a beach cutting board. :shootself:
 
Update. First I filled my 55 gal barrel with cold well water, after the first night I had ice on the top. The outside temp has not risen above 48 deg. But the temp in my E-tank is 60 deg. I did smell a slight odor. Make sure that you do this outside. So a few photos.

1) My E-tank burping

2) The outside tin cover to my stove top oven, rusty. ( note, Lyle will take off some plated metals, so I had to watch this. Time left in 15 min. not heavy rust.)

3) 15 minutes later and a cold water and soap wash.

4) 2 cast iron shelves for the stove top oven. I did not take a before photo. They were rusty, rust free after30 minutes.

4 photos to the right;
https://picasaweb.google.com/114772661409714296598/JeffreyR#6130555500698443186
 
Good deal. How are your anodes holding up? The higher ph that you are using should help protect them better. At your concentration you have a ph of about 12 vs 11 for 1 Tbl Na2CO3 / gal that has been recommended here. I'm running about 12.4 and my anode stays pretty clean.

You are right about having good ventilation, as you evolve H2 at the cathode (work piece) and O2 at the anode. Doing this in a sealed room is just asking for it. BOOM :shootself:
 
So, I just came from taking my BSR stove out of my E-tank. It came out very nice. The only thing that I did was take a small SS wire brush and brush off the heavy rust. I think if I had my pressure washer set up that would have done a better job.

Also my anodes are Clean.

I think the stove was in the E-tank for around 8 or 9 hours.
 
Jeffery,

Thanks for running an independent test. It confirms what I'm seeing. I know how I'm going to proceed from now on. NaOH is the way to go for me. It runs faster, little to no anode cleaning is required and I can use any scrap iron or steel that is laying around instead of having to screw around getting graphite. I also like the results better as it seems to do a better job on the fine features like the stamped markings.

I'm going to run 2.5%, but it is good to know that 0.9% works for you.

I'm not saying that it is for everybody. I'm sure many, if not most, will stay with what they know. To each their own. You do have to treat strong bases (and acids) with respect, but I wear gloves and eye protection with either system.

Since I'm not doing this commercially, I'll probably just run a single tank. This is effectively a lye tank and an e-tank combined. When it gets too filthy, I'll neutralize it with HCl to turn it into rusty salt water before disposing.
 
Hi ShawnE.

I did you the NaOH to 5 lbs. I am thinking about 1 more lb.?:covri:

Everything is staying clean at this time.

I will like to note. I set up an E-tank late last summer using the 2 brush hog blades. I had just replaced them off my brush hog, so they were nice and shinny with no pitting. I had them in the E-tank for 3 weeks. I took them out to clean them, they were all rusty and pitted. I do not see that happening at this time. All is a GO.:icon_thumbsup:
 
From the research that I've been doing, the sweet spot seems to be between 2% and 5%. But as I said earlier, one good test is worth a thousand expert opinions. i.e. "trust but verify" ;-)

I'm running 2.5%, so for 55 gal, that would be 11 Lbs. That would take your pH to 12.4. A 10% solution would have a pH of 13, but that's 44 Lbs. and probably excessive for most things.

If it were me, I'd probably go to around 2%. 8 or 9 Lbs total. This would up your pH to 12.3

Nice not having to clean anodes isn't it? Do you know how much current you are running? What really matters is current density, I shoot for .01A / cm2 to .02A / cm2, but I can only run 20A with my current power supply.
 
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I am going about this as if I was walking on ice. One step at a time. Just like to play it safe. I will be going up to 6 lbs. today. We had snow last night with temps as low as 27 deg. Time to melt some ice.

---------- Post added at 08:01 AM ---------- Previous post was at 08:00 AM ----------

I am going about this as if I was walking on ice. One step at a time. Just like to play it safe. I will be going up to 6 lbs. today. We had snow last night with temps as low as 27 deg. Time to melt some ice. :chuckle:
 
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