Use of the electrochemical impedance spectroscopy to evaluate the performance of a primer applied under different surface preparation methods

Abstract

Electrochemical impedance spectroscopy (EIS) was used in this work in order to evaluate primer behaviour, applied on metals with different conditions of superficial preparation. The substrate surface preparation plays an important role in the final quality of coatings. The cleaning and surface finishing can be carried out using different methods. The most common are sand- and wet-blasting. In this paper the EIS technique was used to evaluate the influence of three different methods of surface preparation (sand-blasting, wet-blasting without inhibitor and wet-blasting with inhibitor). A red epoxy primer was applied on a steel panel, using each of these three clean methods. These primer systems were exposed in a salt atmosphere, which was simulated using a salt-fog chamber during an 870 h exposure time. During this time the electrochemical properties of the primer were periodically evaluated using the EIS technique. Moreover, visual inspection was carried out at the same time as the EIS. The final results of these evaluations confirm the power of the EIS technique to evaluate and determine the best protection performance of a primer applied on steel panels with different superficial preparation.