## Materials Science and Engineering: An Introduction

Calculating the value of K in order to give the CPR in mpy for i in µA/cm2 (10-6 A/cm2), note that the units of A (in µA/cm2 ) are amperes or C/s. Substitution of the units normally used into the former CPR expression above leads to: CPR = K' $\frac{Ai}{nFp}$ CPR = K' $\frac{(\frac{g}{mol}) (C/s - cm^{2})}{(unitless)(\frac{c}{mol})(\frac{g}{cm^{3}})}$ = $\frac{cm}{s}$ Finding CPR in mpy and as i is given in $\frac{ µA}{cm^{2}}$ and for K = $\frac{K'}{F}$, K = ($\frac{1}{96,500 \frac{C}{mol}}$) ($\frac{10^{-6}C}{µC}$)($\frac{1 in}{2.54 cm}$)($\frac{10^{3}mil}{in}$)($\frac{3.1536 \times 10^{7} s}{yr}$) K = 0.129