Fabrication of composite scanning micro pH electrode and its application in localized corrosion

A novel composite scanning micro pH electrode was fabricated. The IrO x-pH electrode produced in a carbonate melt exhibited high stability, a fast potential response and ideal Nernstian response. The slope of the electrode at 15°C was 56.8 mV/pH, which was very close to the theoretical value. The 90% potential response time for a pH change from 1.75 to 13.90 was less than 0.5 s. The composite scanning micro pH electrode is a promising apparatus for detecting the pH distribution on metal/solution interface. pH image on the surface of Al/Cu galvanic couple showed that both the anodic and cathodic areas could be sensed well. Localized corrosion took place on the interface of Al/Cu couple. The localized corrosion developed with time and pH value around the pitting decreased gradually