Simultaneous monitoring of pH and Mg2+ distributions above AZ63 magnesium alloy, either
spontaneously corroding or galvanically coupled with iron, was achieved using SECM in the
potentiometric operation. By introducing an internal micro-reference electrode in a multi-barrel
arrangement of the ion-selective microelectrode used as scanning probe, superior performance
was achieved compared to conventional single-barrel and double-barrel assemblies. In this way,
the impact of the overestimated acidification accompanying metal dissolution using conventional
tips was established from model experiments using non ion-sensitive open micropipettes and pH
antimony microelectrodes. It is shown that the simultaneously acquired pH and pMg maps
provide complementary information on the spontaneous and galvanic corrosion of AZ63
magnesium alloy
