does any body knows about the sparking potential in a phosphate solution with pH=13?
i tried to coat my substrate in the potential range up to 180 V but there was no sign of sparks on the surface, and i think i should get it on potentials around 140-160 V, and i don't know whats wrong!
Hi Ehsan,
The breakdown voltage, above which you observe micro-discharges is a function of several factors including the electrolyte chemical concentration, applied current density, the polarity of the applied power and also your substrate composition. In your question you have not mentioned these factors and this makes it difficult to say exactly at which potential range you should expect the breakdown voltage to happen.
I would recommend increasing the voltage until you see the micro-discharges. Are applying constant current?
Best,
Vahid
Hi dear Dr Dehnavi
Thanks for your answer, yes you are right , the current was not constant, i ramp up the voltage to 180 V (DC) and keep it for 3 minutes, the solution contains 10gr/l Na3PO4+2gr/l KOH+ 4gr/l Ca(CH3COO)2, i think there are some malfunctions with the rectifier i used and i should check its output with measuring instruments.
Best Regards
Ehsan,
Dear Ehsan Ziyaei,
Please refer these papers. I think it may be useful for you..
Dear Ehsan,
In case you're still looking for the answer to that question, I estimate the breakdown voltage for that specific alloy-coating bath system to be well above 200 V, maybe up to 250. If you're restricted on that specific voltage, I would recommend adding F- ions (KF usually) to your solution, which may bring down the break down voltage to the point you're stuck with.
I hope you can find other useful information in our review paper on this subject :
https://www.researchgate.net/publication/315597369_Plasma_electrolytic_oxidation_of_magnesium_and_its_alloys_Mechanism_properties_and_applications
Article Plasma electrolytic oxidation of magnesium and its alloys: M...
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