Question

What is the formula to determine limiting diffusion current density (iL) of concentration polarization?

(a) iL=xnFCB/D

(b) iL=DCB /nFx

(c) iL=DnFCB/x

(d) iL=x/DnFCB

I had been asked this question in exam.

This interesting question is from Modern Theory Principles topic in portion Modern Theory Principles of Corrosion Engineering

Answer 1

Correct answer is (c) iL=DnFCB/x

The explanation is: iL=DnFCB/x is the formula to determine the limiting diffusion current density (iL) of concentration polarization. Where IL is the limiting diffusion current density, D is the diffusion coefficient, CB concentration of ions in bulk solution and x is the thickness of diffusion layer.