Effect of accelerated ageing procedures and flash rust inhibitors on the anti-corrosive performance of epoxy coatings: EIS and dynamic-mechanical analysis

Abstract

The present study reports the combination of electrochemical impedance spectroscopy (EIS) technique with dynamic-mechanical (DMA) properties and pull-out strength to monitor the anticorrosive properties of high solid epoxy coatings on pre-treated carbon-steel surfaces with flash rust inhibitors. For this purpose, five different surface treatments and two epoxy system coatings were employed. The coatings were submitted to corrosion performance testing such as salt-spray, immersion in seawater and cyclic protocol in attempt to simulate marine conditions. The pull-out testing revealed mainly cohesive failure of both epoxy coating systems even after the accelerated ageing process. EIS analysis indicated an increase of the resistive characteristic of the coating after ageing treatment, which was explained by an increase of the crosslink density, as indicated by DMA analysis. The EIS results also suggested slight interfacial effect of flash rust inhibitors since they presented a major coating resistance than hydroblasted panels. Therefore, unlike the expected degradation after artificial ageing, the two high solids epoxy coating systems kept and even presented increased barrier property after ageing. Furthermore, no negative influence of wet surface preparation with or without inhibitors was observed in this study.