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

The anti-corrosion improvement of epoxy-based (EP) coatings through an eco-fridendly way is significant to industrial development. Phytic acid (PA) is a kind of natural corrosion inhibitor, but its use to enhance the anti-corrosion of EP is challenging due to their poor compatilibility. This problem is addressed by the modification of PA in this paper. First, PA is grafted to ethylene glycol diglycidyl ether (EGDE) to obtain modified PA (PA-EGDE) by the catalysis of tetrabutylammonium bromide. Subsequently, PA-EGDE is added to EP to fabricate PA-EGDE/EP coatings. When the PA-EGDE loading is 5 wt%, the PA-EGDE/EP coating exhibits best mechanical and anti-corrosion properties. The peeling force and adhesion failure rate are 2.03 MPa and 45.6%, and the hardness, flexibility and shock resistance are 2H, 1 mm and 50 cm, respectively. The corresponding Ecorr value of PA-EGDE/EP coating is -0.620 eV, which is much higher than that of EP coating (-0.797 eV); the impedance modulus is 108 omega center dot cm2 after immersion in 3.5 wt% NaCl aqueous solution for 30 days, which is much bigger than that of EP coating (106 omega center dot cm2). Moreover, the anti-corrosion mechanism of PA in EP coating is thoroughly discussed.