Dear Mr. Ihsan, in galvanic corrosion, area effect or the ratio of cathodic to anodic area is so important. The larger cathodic area compared with the anodic , the more oxygen reduction, or other cathodic reaction can occur, and hence greater galvanic current leads to increase the corrosion rate.

Dear Osamah,

I´m not an expert on corrosion, but in such situation you have a small piece (volume) of material providing electrons to a large piece of material. Therefore, the rate at which electrons leave the anode is higher, so is the corrosion rate.

Sergio

Dear Osamah,

The influence of cathode/anode area ratio is a key factor to the rate of galvanic corrosion in seawater. It can be explained that the anode current is always equal to the cathode current when the galvanic corrosion occurs, and anode area is smaller, the anode current density is greater. That is, the corrosion rate of anode metal is greater. Increasing Sc/Sa accelerated galvanic corrosion rate of high potential difference coupling, the fitting curves of the galvanic current by experiments will show the parabola shape. When anode density is greater than corrosion rate will be higher. Galvanic corrosion rate linear growth with the Sc/Sa in seawater indicates, the galvanic potential shift and driving voltage decreases.

Hope it is helpful for you.

Ashish

Dear Dr. Osamah Ihsan Ali,

it can be explained that the anode current is always equal to the cathode current when the galvanic corrosion occurs, and anode is smaller, the anode current density is greater. That is, the corrosion rate of anode metal is greater.

For more details, please see the source:

-Area Ratio of Cathode/Anode Effect on theGalvanic Corrosion of High Potential DifferenceCoupling in Seawater

Zhijian Wang et al, IOP Conf. Ser.: Mater. Sci. Eng.322 022046 (2018)

Available, as open access, at: https://iopscience.iop.org/article/10.1088/1757-899X/322/2/022046/pdf

Best regards, Pierluigi Traverso

I am very grateful to you Pierluigi Traverso

I am very grateful to you Sergio Cicero

I am very grateful to you Ashish Thakur

Thank you.

Dear Osamah

In general, in equilibrium chemical reaction;

M------ Mn+ ne & Mn+ne--------M , where M is solid metal, Mn is a number of M cations, and ne is a number electron.

There is anodic current ( Ia) that corresponds to M------ Mn+ ne , the anodic reaction and there is cathodic current (Ic) that corresponds to Mn+ne--------M, the cathodic reaction. In this case the Ia=Ic= exchange current (Ie). In other words, the net exchange current rate =0= Ia-Ic=0. So, for Ia to be more dominant, more corrosion rate, than Ic, the net exchange current rate should be >0, = Ia-Ic>0. Since the net exchange current rate is inversely proportional to the exposed area of an anode, therefore, it is expected that the Ia would be higher than Ic.

Dear Mr. Ihsan, in galvanic corrosion, area effect or the ratio of cathodic to anodic area is so important. The larger cathodic area compared with the anodic , the more oxygen reduction, or other cathodic reaction can occur, and hence greater galvanic current leads to increase the corrosion rate.

I am very grateful to you dear Habib

I am very grateful to you dear Maryam

Pls, consider the cathodic-anodic area ratio