Acrylic polyol/silicone coating corrosion protection analysis using electrochemical impedance spectroscopy

Abstract

Purpose – The purpose of this paper is to develop different combinations of acrylic polyol and silicone resins with various weight ratios and to test the coating properties using electrochemical impedance spectroscopy (EIS). Design/methodology/approach – The performance properties such as coating resistance, capacitance, dielectric constant, water uptake and diffusion coefficient were evaluated using EIS with exposure to 3.5 per cent NaCl solution for 60 days. Findings – The binders developed in this study were coated on cold rolled steel plates. The dry film thickness was found to be in the range of 50 microns. From EIS results, it was found that Acrylic polyol sample with 30 weight per cent of silicone exhibits the best properties, as it has high coating resistance in the range of 109 Ohms for the full period of exposure, whereas all other samples showed poor performance with the exposure time. For these samples, the parameters measured such as the coating resistance of the samples decreased while the coating capacitance, percentage of water uptake and diffusion coefficient of the samples increased after being exposed to corrosive solution for 60 days. The coatings developed by 0, 10 and 60 weight per cent silicone showed high coating capacitance on the first day of exposure, and these systems failed early during the exposure. The water uptake percentage and diffusion coefficient of all samples were found to be less than 50 per cent and below 10-11 cm2 s−1, respectively. An optimum cross-linking between the resins is considered as the main contribution for the best performance shown by the sample that consists of 30 weight per cent of silicone in acrylic matrix that provides maximum barrier properties of the coating. Originality/value – Developing coatings using hybrid binders (silicone resin and acrylic polyol resin) is new area of research. This will explore more research in the formulation of novel coatings.