Preparation and study of modified phytic acid/epoxy resin anti-corrosion coating

Abstract

Abstract The anti-corrosion epoxy-based coating is crucial for industrial development. Improvement of the anti-corrosion of epoxy-based coatings through a simple, effective and eco-friendly way is of great significance. Phytic acid (PA) is a kind of natural and eco-friendly corrosion inhibitor, however, the compatibility problem between PA and epoxy resin (EP) is not good. This problem is addressed by the modification of PA in this paper. PA is grafted to ethylene glycol diglycidyl ether (EGDE) to obtain modified PA (PA-EGDE) by the catalysis of tetrabutylammonium bromide under mild conditions. Subsequently, PA-EGDE is added to EP to prepare PA-EGDE/EP coatings. When the PA-EGDE loading is 5 wt%, the PA-EGDE/EP coating exhibits excellent mechanical and anti-corrosion properties. The hardness, flexibility and shock resistance are 2H, 1mm and 50cm, respectively, which are as good as those of pure EP coating. The Ecorr value of PA-EGDE/EP coating at 5 wt% PA-EGDE loading is -0.620 eV, which is much higher than that of EP coating (-0.797 eV); the impedance modulus is 108 Ω·cm2 after immersion in 3.5 wt% NaCl aqueous solution for 30 days, which is much bigger than that of EP coating (106 Ω·cm2). Otherwise, the anti-corrosion mechanism of PA in EP coating is thoroughly discussed.