In-situ imaging of chloride ions at the metal/solution interface by scanning combination microelectrodes

Combination solid silver-silver chloride (Ag-AgCl) and liquid membrane Cl ion-selective microelectrodes were designed and constructed. These microelectrodes, which had a micrometer-sized tip, contained two compartments: one served as the reference electrode arid the other as the Cl ion-selective electrode. The microelectrodes were used to map in-situ Cl- ion distribution in several localized corrosion systems. When used with a computerized scanning stage, the microelectrodes provided information on the distribution of Cl- ions near the metal/electrolyte interface. Cl- ions were observed migrating toward and accumulating near the anodic region forming, a "Cl- ion-rich island" on the metal surface. Scanning combination Cl- ion-selective microelectrodes may provide a useful tool for mechanistic studies of localized corrosion.