Bio-based one-component epoxy resin: Novel high-performance anticorrosive coating from agro-industrial byproduct

Abstract

In this present work, an epoxy resin produced from an agroindustrial byproduct, cashew nutshell liquid (CNSL), was used for manufacturing a one-component anticorrosive epoxy coating. CNSL-based epoxy resin (e-CNSL) was synthesized using a solvent-free methodology with performic acid generated in situ. The chemical structure of resin was evaluated by FTIR and 1H NMR. The curing parameters of the epoxy-phenol system with 1-methylimidazole (1-MIM) as an accelerator were investigated by differential scanning calorimetry (DSC). The use of only 5% by weight of 1-MIM was efficient to catalyze the reaction, obtaining the lowest cure temperature (150 °C). The coating showed high crosslinking and good thermal-mechanical performance, where the initial decomposition temperature was 200 °C and glass transition temperature was 30 °C. The anti-corrosive performance of e-CNSL/MIM5 exposed to salt spray and 3.5% w/v NaCl solution was monitored by electrochemical impedance spectroscopy, adhesion, and visual evaluation during the exposure period. Humidity test with visual evaluation was also performed. The coating presented high impedance module at 108 Ω.cm2 and high adhesive property, suffering low delamination during the tests. Thus, the one-component bio-based coating developed is promising to be applied for corrosion protection purposes.