In-Situ Imaging of Chloride Ions at the Metal/Solution Interface by Scanning Combination Microelectrodes

Abstract

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 and 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.