Advances and Application of Scanning Vibrating Electrode Technique on Coated Mild Steel under Cathodic Protection

摘要

An in situ Scanning Vibrating Electrode Technique (SVET) was employed to investigate corrosion activities on coated mild steel in thin layer sodium chloride solutions at free corrosion potential and under cathodic protection. Besides of the processes of applying impressed current cathodic protection, this technique was introduced to monitor electrochemical processes occurring at the surface of coated steel when electrically connected with sacrificial anode. Thanks to the high spatial resolution and sensitivity, a SVET system could investigate local anode current density, cathodic active area, and the corresponding changes with time on as-received epoxy coated steel and calcareous film covered steel samples. The work will also present results from corrosion sample obtained by external simulated tidal instrument after different exposure time, in order to determine the interaction between cathodic protection and coating in this environment. Techniques used to understand the performance have included optical photography, white light interferometry, together with Scanning Electron Microscopy (SEM). Further investigation of other electrochemical analytical methods, for example localised electrochemical impedance spectroscopy, could also be used in this study to evaluate corrosion progress over a few days.