Application of AC-SECM in corrosion science: Local visualization of heterogeneous chemical activity in AA2024 surfaces

Abstract

Aluminium alloy AA2024-T3 surfaces have been characterised by using a new microelectrochemical technique, frequency-dependent alternating current scanning electrochemical microscopy (AC-SECM), which does not require the addition of any redox active species to the electrolyte solution. Information regarding the topography and/or redox activity of the solid/liquid interface is obtained in situ, allowing their evolution with time to be monitored with high spatial resolution. By scanning the microelectrode over the surface, an image is generated, as well as information concerning reactions that take place in the solution space between the tip and the sample or on the surface of the scanned sample. A heterogeneous response due to the presence of intermetallic inclusions precipitated in the material is found on AA2024-T3 surfaces. The highly localized anodic activity was thus detected, which has been interpreted as a result of the galvanic coupling between the matrix and the intermetallic particles