New interpretation of electrochemical data obtained from organic barrier coatings

After a short introduction into the usage of organic barrier coatings and s ome related problems of evaluating coating performances, the principles of relaxation voltammetry (RV) measurements are given. RV is a new electrochem ical technology in the time domain. The new features of this technology are high sensitivity and a relatively high sampling rate. This allows the meas urement of the coating resistance R-C and of the coating capacity C-C even if good barrier coatings are used. RV offers a two-step data interpretation : first a very direct and easy accessible extraction of R-C and C-C. Second , a much more detailed interpretation of electrochemical processes in the c oating is offered, i.e. dielectric relaxation, diffusion and charge transfe r. In addition to the more classical interpretation of impedance spectrosco pic data, RV permits a more detailed understanding of physical processes an d their contribution to the relaxation of the previously charged coating su rface. Evidence that the interpretation of barrier coatings by using only-R C elements is not suitable for the description of time-domain-measurements of immersed samples is given. The newly derived model based on RV-data is a ble to describe a huge number of coating materials under quite different ag ing conditions. (C) 2001 Published by Elsevier Science Ltd.