Time evolution of Electrochemical Impedance spectra of cathodically protected steel in artificial seawater

- Usability of EIS data for better cathodic protection control was investigated.
- Time evolution of Electrochemical Impedance spectra was evaluated.
- Quantity of physical and electrochemical processes was evaluated by usage of Chi2 function.
- EIS proved to be useful for hydrogen evolution detection.

Usability of Electrochemical Impedance Spectroscopy data for better cathodic protection control was investigated. Carbon steel - S235JR2 grade specimen were exposed in artificial seawater environment. Samples were polarized and their potentials corresponded to four different cathodic protection degrees. Time evolution of Electrochemical Impedance spectra was investigated. Goodness of fit function (X2) was analysed in terms of proper time-constant quantity determination. It was possible to observe and detect occurrence of new phenomena by X2 evaluation. Weight-loss corrosion coupons were used to calculate corrosion rates. At initial stage of exposition impedance measurements complemented proper protection potential data. Quantity of physical and electrochemical processes was evaluated and linked to the state of specimen providing valuable supplementary data. EIS proved to be useful for hydrogen evolution detection which is a great risk which has to be recognised and prevented.