EIS and organic coatings performance: Revisiting some key points

The objective of this work is to gather historical aspects about the use of EIS for evaluation of corrosion protective organic coatings performance, emphasizing experimental care, contributions and limitations for wider technological application. Contributions are rescued from authors who made important work in development and evaluation of organic coatings with the support of electrochemical techniques. The knowledge of these fellows in organic coatings paved the way for the use of EIS in this field; particularly, some contributions of J.E.O. Mayne are reverenced. This paper does not provide a complete review of the subject, but rather outline keypoints, that were selected according to their relevance in the technological applications to which impedance measurements could contribute, as: early detection of underfilm corrosion, indirect measurement of delaminated areas, prediction of coatings service life by water uptake and modeling with analog electric devices as a tool to obtain the parameters needed for the mentioned applications. Fundamental aspects of EIS in this field have extensive literature which is referenced. The massive current use of EIS justifies this retrospective, revisiting some basics as a source for new users, sharing critical comments and reinforcing the importance of some experimental care.