Relationship between the isoelectric point (pHpzc) and the potential of zero charge (Epzc) for passive metals

The potential of zero charge of oxide-covered metals (Epzc) is shown to be linear function of the isoelectric point of the oxide film (pHpzc). The linearity is displayed for 14 different metals having n-type semiconductor oxide films and for three metals having p-type semiconductor oxide films. Using experimental values from the literature, the slope of the linear plot of Epzc vs. pHpzc is observed to be −0.142 V for n-type oxides and −0.115 V for p-type oxides. The theoretical slope is −0.120 V, which is derived in this communication.