Development of a methodology based on odd random phase electrochemical impedance spectroscopy to evaluate corrosion protection of coatings

Commonly coatings are used to protect metals from corrosion. Different types of coatings are available and according to their characteristics they provide different levels of protection. In order to evaluate the performance of the coating, it is fundamental to have a methodology that is reliable and efficient even when applied to different kinds of systems. A good candidate technique to develop this methodology is the Electrochemical Impedance Spectroscopy (EIS). Among the advantages provided by this technique there are the ability to detect corrosion and the fact that the measurements are nondestructive. Recently Odd Random Phase Impedance (ORP-EIS) was developed. In comparison to classic Impedance, it allows for a reduction of measurement time by gathering information over a broad frequency range with a single measurement. In addition to that it is also possible to have direct information about the steady-state condition of the system by evaluating the recorded noise levels. The methodology consists in the use of ORP-EIS combined with aging procedures. It is applied to different organic coated systems with different characteristics, including self-healing ones. Part of the coatings are applied on the same type of substrate, hot dipped galvanized (HDG) steel, in order to isolate the information uniquely linked with the protective layer.