Electrolysis: Distance btw anode/cathode, current, and more

T

TFlood

New member
Hi Everyone, here's my questions regarding electrolysis:

- I have 2 options for optimal electrolysis, before my charger shorts out. It's a 6V/12V 6A. The scale maxes at 8A. If you get the current too high, the scale seems to flip back and forth from 0A to 8A about every 2 seconds!
Option A) 6V with about 4A and anode is closer to cathode
Option B) 12V with 6A and anode is further from cathode
Which is optimal for cleaning the cathode piece?

- What does everyone aim for regarding current magnitude?

- If my charger displays "6A" output on the label, yet I can get the needle to 8A, is it wise to stop at 6A, considering wire insulation ratings that it is built with?

Any help from someone who is CONFIDENT with their answers would be super sweet!

Cheers
 
I don't think there's a "one size fits all situations" setting. I use my charger in the same mode all the time, and see quite a bit of difference in amperage from piece to piece which may or may not be related to mass or surface area. Since I'm not an electrical engineer, I'll confine my thoughts to those I feel confident about.

Most people find a 12 volt/2 amp manual charger sufficient for general cast iron cleaning. Since many moderately priced manual chargers are 2 amp/10 amp switchable, the 10 amp setting is typically used, and seems to be more efficient than the 2 amp under identical circumstances. Higher amperages may work somewhat faster, but appear to just create more heat than anything else. Mine seems to work just fine on the 10 amp setting, and it's pulling about 6-8 amps when good connections are made.

I haven't found cathode/anode separation to be an issue one way or the other. My tank dimensions would not let me hang a piece further away than about 12" anyway. I think a broader anode surface area works better, so sheet metal for me has performed better than things like rebar rod.

Rather than volts, amps, and distance, I think more depends on how well your clamps are making metal-to-metal contact. Crud is a good insulator, as is rust to a degree. Some manual pre-cleaning with a SS wire brush of the cathode contact point is often helpful.

The 0A/8A flip-flop you describe is puzzling. In the hundreds of pieces I've cleaned, I have not seen that behavior. Perhaps there is an issue with your particular charger or the connections. Is it a manual charger, or if an automatic one that can be set to a manual mode, are you using it as such?
 
Thx for your input.

I have nice big steel plates for anodes. Tried the rebar, but it sucks.

Regarding your comment about cruddy connections: this will directly impact current magnitude. According to Ohm's Law, I=V/R (where I is current in amps). More crud = increase in R, thus lowering I. Hence, degree of "cleanliness" in connections is concerning current.

My own thoughts about distance is that it puts more resistive water (more R) between anode and cathode, so higher V is necessary to overcome this. In conclusion re: distance, lets say you use a lower V and less distance and happened to get 5A. Now reconfigure so distance is greater, but uses more V, and you happen to achieve again, 5A. My hunch is that the cleaning process may work the same in either circumstance. I think that with less distance, the crud is more likely to make it from cathode and stick to anode. With more distance, it might come off the cathode, then "swim" around in the water until it eventually finds the anode to which it sticks onto.

Regarding my charger, I am not sure the difference between manual and automatic. It just has 6V or 12V.
 
An automatic charger has circuitry to shut it off when the battery is fully charged. It also sees a skillet as a charged battery.

I haven't really bothered to try to apply scientific principles to my electro tank. As long as the meter is reading towards the higher end of the scale, the electrolyte is fizzing, and the piece is coming clean, I'm happy.
 
From a purely scientific point of view:
Resistance is proportional to the distance between the electrodes.
Resistance is inversely proportional to the surface area of the electrodes
Resistance is varies non-linearly with temperature. Hotter solutions conduct better.
Resistance varies with the amount and type of electrolytic solution, up to a concentration limit.

From an engineering point of view: Stop trying to optimize it and just get it working. All these variables don't make that much difference to actually getting the pan clean. :) And optimizing just makes your head hurt.
 
David: I agree with your statements regarding resistance. I'm interested in the physics because I'm an electrical engineering technologist student.
 
TFlood said:
...I have 2 options for optimal electrolysis, before my charger shorts out. It's a 6V/12V 6A. The scale maxes at 8A. If you get the current too high, the scale seems to flip back and forth from 0A to 8A about every 2 seconds!

Any help from someone who is CONFIDENT with their answers would be super sweet!
Click to expand...
Are you using an automatic or manual charger? What is the model #?
It is doing this becuase it is either overloaded, or thinks it is done.

I am using a manual charger at 12V/8amps and mine will do this when it is drawing too much current. I'm sure it is an internal overload that kicks in to protect the charger. When this occurs the charger will also be pretty warm.

To fix this you need to reduce the load. I do this by reducing the amount (quantity) of the anode. One tool that I have found VERY useful to read the amp draw is a clamp on ammeter like this:

4bsRB8Kl.jpg


You simply clamp it around one of the leads (positive or negative...not both!) and it tells you the amp draw. It is a good way to confirm that your connections are good and that you aren't overloading the charger or wire. I use it every time I put a new pan in or adjust my setup.

This is the tub I am using - Brute 28 gallon square Trash Container.



I like it because it is large enough to easily put 2 pans in side by side and deep enough to hang a #12 and have it submerged. It is also sturdy enough when filled. I do like the square style as well for arranging the pieces and the anode. The is a recessed area around the outside on the bottom that holds the anode so it doesn't slip out and hit the pans. Not a big deal, but sort of nice.

I also got the lid with the tub. It is my understanding that you never need to replace the washing soda solution. Yes it may be gunky and look gross, but as long as it is conductive then it will do the job. I have skimmed the top "residue" from time to time. On the flip side, washing soda and water are cheap. :-)

Hope this helps!
Dan
 
Hi DSpang... thx for you input. Here's some interesting info I found about current/voltage from http://myweb.tiscali.co.uk/andyspatch/rust.htm

The writer states, I think, you should aim for 1mA per square centimeter of the cathode exposed, but it's a little unclear in his writing. I dont know if this means all sides of your cathode or only that which faces the anode, or maybe he's talking area of both cathode and anode. One can play with voltage settings and resistance variables such as distance or series loads to try to achieve this.

One notable thing he points out is that too much current can result in "split up into its component parts resulting in large amounts of explosive hydrogen being evolved at the cathode".. I think what this guy is getting at is too much current is not ideal.
 
TFlood said:
Hi DSpang... thx for you input. Here's some interesting info I found about current/voltage from http://myweb.tiscali.co.uk/andyspatch/rust.htm

The writer states, I think, you should aim for 1mA per square centimeter of the cathode exposed, but it's a little unclear in his writing. I dont know if this means all sides of your cathode or only that which faces the anode, or maybe he's talking area of both cathode and anode. One can play with voltage settings and resistance variables such as distance or series loads to try to achieve this.

One notable thing he points out is that too much current can result in "split up into its component parts resulting in large amounts of explosive hydrogen being evolved at the cathode".. I think what this guy is getting at is too much current is not ideal.
Click to expand...
That is a very interesting article! My interpretation of what he said is 1 mill-amp per sq cm of the entire cathode (the piece being de-rusted). This equates to 6ma per 1 sq inch or 1 amp of current for every 166 square inches or 1.15 sq feet.

I did a rough calculation on a 12" diameter skillet and came up with approx 308 sq inches (assuming 2" high sides and a 5" long x 3/4 wide handle)
Applying his 1ma per sq cm I get 1.98 amps for a 12" skillet. So clearly I am using too many amps when I put a single pan in and apply 4 amps.

This statement interested me
"Put simply, if too high a current is allowed to flow from the start, the deposited iron will be very porous and possibly become detached from the surface and the rapid hydrogen bubble production can blast off rust which could possibly have been recovered using gentler methods."​

I guess I didn't realize that part of the anode is being deposited on the pan, but it does make sense. I did some searching and found a great article that talks about this issue and why a carbon anode is preferred. http://www.fordgarage.com/pages/electrolyticderusting.htm
He states
"One major advantage of using carbon (graphite) material for the anode is that no iron is deposited on the part. Instead, the part gets a loose 'plating' of carbon, which is pretty easily washed and brushed off, and does not promote subsequent re-rusting."​

Hmmm...this makes me really wonder if we are compromising the surface of our pans when we somewhat haphazardly apply amps via a battery charger. I saw plenty of bubbles and figured it was working great! Add some more anode and got even more bubbles...even better no? Maybe not!

Has anyone experienced this or notice any degradation of the part due to how the iron is deposited? You may not notice it on a pan that is already pitted and has a less than perfect surface, but I have a couple that still have very clear factory milling marks and I'm not interested in changing that surface, even slightly.

I guess I'm going to hunt for some carbon anodes before I do any more pans and try doing it at a lower amp setting!

Thanks for the reference!
 
Cool man, looking forward to hearing more on your results! I really haven't done enough electro to get a feel for what current is optimal. Good luck.
 
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