We report on the fabrication of pH microsensors and the adaptation of their vibration characteristics for an operation as scanning probes in a constant-distance mode SECM. The application of these pH-sensitive probes for measuring changes in local acidity/basicity by means of potentiometric constant-distance SECM will be presented. Furthermore, it will be shown that this approach has the capability to visualize the process of localized corrosion occurring at microscopic defects in the passive oxide layer on the surface of NiTi shape memory alloys.