What happens to Electrical Conductivity of the electrolyte when the electropolishing solution ages?

[BVKrish]

Hello Everyone,
Would someone here help me with this question:
What happens to the Electrical Conductivity of the electrolyte when the electropolishing solution ages?
Will it increase or decrease?
I am considering a mixture of Sulphuric acid, Phosphoric acid and water.
Thanks.

 

[EdStainless]

These are so conductive I am not sure that you could see the difference.
We used to actually measure the various metals in the solution.
This was done with a combination of using additives and ion specific probes in the lab.


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P.E. Metallurgy, Plymouth Tube

 

[Metalero]

Conductivity decreases because the ions involved in electropolishing get used up during use. The attached graph shows that the limiting current density value at 30o C is lower for an electrolyte that was previously used for 5 h of electropolishing, compared to fresh electrolyte.

 

[EdStainless]

The issue is that most simple conductivity meters work at very low voltage and current, and you don't see it there.
Yes, at working voltage (over 5V) you can see the effect of use.
Though you have to be careful to distinguish acid depletion from metal loading, both have an impact.

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P.E. Metallurgy, Plymouth Tube

 

[BVKrish]

Thanks for the answers.
I was performing a set of experiments with the same solution (Sulphuric acid, phosphoric acid, water) today.
And, every time I measured the Conductivity value after each test, I could see that there was an increase.
I couldn't understand why this happened when I was expecting a decrease.
Would someone help give me some inputs on this?

 

[EdStainless]

I'll bet that you were measuring at very low current density.
I such a highly conductive solution every little detail matters.
You also need to have good control over the temperature.

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P.E. Metallurgy, Plymouth Tube