Combined amperometric/potentiometric probes for improved chemical imaging of corroding surfaces using Scanning Electrochemical Microscopy

Chemical visualization of corrosion processes using scanning electrochemical microscopy (SECM) in combined amperometric/potentiometric operation has been achieved by developing novel multi-barrel probes as tips. A Pt-based amperometric disc probe is employed for the detection and characterization of reactive sites on a corroding system, whereas a Sb-based disc microelectrode is employed to visualize local solution pH changes. Quasi-simultaneous imaging of localized corrosion micro-cells on the surface and the associated pH variations in the electrolyte, resulting from both the electrolysis of dissolved metal ions from the local anodes and the consumption of an oxidizing agent at the local cathodes, can be obtained in the same solution without changing the probe. Galvanic corrosion of a model Cu-Fe pair in chloride-containing solution was visualized with high spatial resolution by recording either line scans or 2D-images using the novel Pt/Sb multi-barrel tip.