Scanning Microsensors for Measurement of Local pH Distributions at the Microscale

Ion-selective pH microelectrodes were used to measure hydroxide ion concentration fields produced by electrochemical reduction of oxygen on 10 and 25 {micro}m Pt disk electrodes. The sensors were mounted on a scanning system, and the hydroxide concentration profiles over the disk electrodes were obtained. Data were compared with predictions based on the diffusion equation. The pH microelectrode was also used to verify the buildup of hydroxide ions generated by cathodic reaction on Al{sub 3}Fe that was in electrical contact with Al 6061 at the rest potential in 0.6 M NaCl.