AC IMPEDANCE TECHNIQUE FOR ACCELERATED EVALUATION OF COATED STEEL SUBSTRATE

The main aim of this preliminary research study was to introduce the Electrochemical Impedance Spectroscopy as a new instrument to be introduced to the Trainer of the Welding Department at Industrial Institute Shuwaikh as a training tool in the laboratory for the evaluation and screening of different coatings on steel substrate. In this respect a training and research investigation has been held on EIS at Construction and Building Materials CBM / KISR for Eng. Emad Malallah who is an Trainer at the Welding Department. The technical report consists of the following training sessions and research study:  Literature Survey on different types of paints and protection mechanism  Electrochemical Impedance Spectroscopy EIS; Theory and Lab Practice  Experimental application of EIS on different generic type of coatings in order to understand the Impedance and capacitance response over a wide frequency range of 0.01 Hz to 100 KHz.  The selected Paint system that has been investigated consists of; Clear Polyurethane Paints (C1 C2), HB Phosphate Primer (S1 S2), and Zinc Epoxy Polyamide (ZE); as well as un-painted bare steel substrate (BP BN). The painted steel substrate was immersed in 3%NaCI solution for test duration ranging from 0 hrs. to 337 hrs. The AC Impedance results have indicated variation in the performance and deterioration behavior of the various paint system employed. The values of the paint film capacitance (Cc) and resistance (Ppo) were recorded experimentally from Nyquist plots. Photographic and SEM photomicrographic examination were obtained for the coated steel substrates. Finally, the EIS data obtained were used for ranking of the different selected paint systems according to the highest paint performance in Sodium Chloride solution and the paint surface free from the on sit of corrosion products, blisters or rust. The overall results have indicated that the best performance in terms of ranking were obtained for: ZE S2 CI