Effects of surface modifications with ABP/ATP on the water permeation behaviors of epoxy, and their application to the corrosion protection of the epoxy coated steel

Abstract

An epoxy coating system was designed to evaluate the relation between chemical structure and corrosion protection, by curing the epoxy coatings with different hardeners. The hydrophilic tendency of cured epoxy with different hardeners is more appreciable in the epoxy coatings cured with polyamide-epoxy adduct based on the examination of chemical structure and It was evident that the hydrophilicity of epoxy coating was changed depending on the hardener and it is more appreciable to confirm the high hydrophilic property when the curing was done by a polyamide-epoxy adduct. Water diffusivity and water uptake into the epoxy coatings cured with polyamide were much lower than those into the epoxy coatings cured with polyamide-epoxy adduct. The effect of hardener on the retardation of water transport is more appreciable in the coatings cured with polyamide, which is generally proportional to the hydrophilic tendency of epoxy coatings measured by the contact angle test. The decrease in the impedance modulus |Z| at low frequency region with cycling in hydrothermal test for epoxy coatings was associated with the initiation and growth of localized corrosion on carbon steel. The occurrence density of corrosion spot of coated carbon steel generally decreased with hardener of polyamide, confirming that corrosion protectiveness of the current epoxy coatings are well agreed with their water transport behavior. An epoxy coating system was designed to give hydrophobic properties on its surface by modifying the epoxy with amino branched polydimethylsiloxane (APB) and amino teriminated polydimethylsiloxane (ATP) and then we examined the effects of the surface modification on the structure including phase separation between top and bottom of coating, hydrophobic surface properties, water transport behaviors, EIS, and corrosion protection of the modified epoxy coatings. When compared the results of epoxy coating modified with ATP and modified with ABP, it is evident that the epoxy ...