Investigations on corrosion inhibition performance of self-healing nano-clay modified epoxy coatings

Abstract

Motivated by the need to mitigate corrosion and improve the lifespan of concrete structures, we report in this paper the results of our experimental investigation using hybrid nano-modified epoxy coatings for mild steel bars in concrete using a combination of nano-clay and self-healing tung-oil microcapsules. The prepared nano-modified coatings were characterized by Field Emission Scanning Electron Microscopy (FE-SEM) and Fourier Transform Infrared Spectroscopy (FT-IR). They were applied on plain mild steel bars and subjected to accelerated impressed current corrosion. Their performance was assessed by non-destructive electrochemical corrosion current and ultrasonic guided wave measurements. These assessments were corroborated by visual inspection and destructive testing parameters of residual mass loss and tensile strength. Coated rebars were also subjected to simulated damage to investigate the self-healing capabilities of the prepared coatings. Both non-destructive and destructive results demonstrate that hybrid nano-modified coatings utilizing nano-clay (2 wt% of epoxy resin) with self-healing tung-oil microcapsules (10 wt% of epoxy matrix) are effective in inhibiting initiation as well as progression of corrosion made possible by a dual-protection mechanism. Initiation of corrosion was delayed effectively due to the paths of diffusing aggressive ions made tortuous by nano-clay modification. In addition, the progression of corrosion was arrested by self-healing tung-oil microcapsules. We believe these results could provide an important tool in reaching the goal of sustainable construction.