A pH sensing channel flow double electrode was developed for pH detection of magnesium dissolution during anodic polarization. Because the hydroxide ions generated during the anodic polarization of a magnesium working electrode (Mg-WE) flow to a tungsten pH sensor (W-pH) downstream of the Mg-WE, pH changes can be detected by measuring the rest potential of the W-pH. A video recording of the Mg-WE surface was performed during the measurement, indicating that increase of pH was related to the film breakdown on Mg-WE surface. The hydrogen evolution rate of the order of 10(-8) mol cm(-2) s(-1) was estimated from pH values. (C) 2018 The Electrochemical Society.