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

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Product Number: 51315-5946-SG

ISBN: 5946 2015 CP

Author: Wei Shi

Publication Date: 2015

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The long term protection of metal structures exposed to a marine environment is a problem which needs to be approached from many different points of view. Early studies of continuous steel strips steel sheet piling and also closely spaced individual electrically isolated or electrically connected coupons in the marine tidal zone show severe corrosion losses although the corrosion profiles were very different. There are indications that even under conditions of cathodic protection levels of corrosion observed around the mean high tide level are slightly greater than those in the low tide to mid tide region.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 together with Scanning Electron Microscopy (SEM). Further investigation of other electrochemical analytical methods for example localised electrochemical impedance spectroscopy (LEIS) are also used in this study to evaluate corrosion progress over a few days.