Dear Sana Mirza

The electrode potential does not depend on the surface area of the electrodes. Please recall the Nernst equation to see how it is a chemical thermodynamical relationship out of the electrodes surface area.

Best regards

Dear Mohammed Hussein j. H. Al'Atia

Thank you for your feedback. I have a follow-up question: Please let me know if my following thoughts are correct.

I think if the sample area is large it would result in a large cathode to anode area ratio which would, in turn, increase the corrosion current and shift the corrosion potential in the positive direction.

Dear Sana Mirza thank you for your kindly feedback. The integrity of the surface protective layer formed on sample or the integrity of precoating layer applied on the sample are only the factor affected the sample corrosion potential as, at higher integrity (less defects), the area ratio available for cathodic to anodic area become higher and accordingly Ecorr little increase positively and the current density become lower in value. Now, you can increase the sample area, this will increase the corrosion current but the corrosion current density continue the same. Please remember that corrosion current density = corrosion current/sample's surface area.

Best regards

No , there is no relationship between Ecorr and the surface of sample .

Dear Mohammed Hussein j. H. Al'Atia , Sana Mirza

Thanks for your comments that helped me get deeper into this topic.

However, I would like to contribute with my opinion. Based on the following equation, Ecorr value in a given solution is a function of the ratio between active ion concentration of the dissoluted metal and reducing agents from the solution:

Ecorr=E0 + (RT/nf)x ln(aMn+/aXn- )

If I understand it right, once we lower down the active area of an anode this should cause negative not positive shift in Ecorr value because the ratio between aMn+/aXn- becomes lower. I have this experience by performing PEO coating on magnesium alloys where Ecorr is regularly shifted towards more negative values comparing to the bare substrate.

Please let me know if my ideas are correct.

Best regards.

Dear Milan Strbak

Thank you for your kindly feedback and I would like you to distinguish between the area of the sample, as in the question by Sana Mirza , and the area available for cathodic and anodic reactions on the sample surface. In this case, the Ecorr is closely depend on the variation in the ratio of the area available for cathodic and anodic reactions Ac & Aa which is highly depend on the type and integrity of the coating systems that working on the sample surface.

Best regards

Dear Mohammed Hussein j. H. Al'Atia

Thank you for your kind response it helped me to distinguish the area of the sample and the area available for cathodic and anodic reactions on the sample.

Best regards.