Progress in scanning electrochemical microscopy by coupling potentiometric and amperometric measurement modes

Abstract

Scanning electrochemical microscopy (SECM) with coupled potentiometric and amperometric measurement modes is used to study corrosion reactions in aqueous environments. Whereas conventional electrochemical techniques lack spatial resolution and provide little information on behaviour at sites of corrosion initiation or at defects, the advent of scanning electrochemical microscopy is contributing to overcome these limitations when applied to the investigation of corrosion processes in situ. Ion-selective microelectrodes (ISME) and dual amperometric/potentiometric probes have been developed that can be employed as SECM tips as they exhibit sufficiently low resistances and response times. The applicability of this experimental approach is demonstrated by chemically imaging the behaviour of an iron-magnesium galvanic couple immersed in a diluted aqueous electrolyte. The dissolution of metal ions from anodic sites, the consumption of oxygen at the cathodic sites, and the local pH changes associated with both half cell reactions are thus effectively monitored