Development of BPA-free anticorrosive epoxy coatings from agroindustrial waste

Epoxy resins are a versatile class of thermosetting precursors. The most commonly used compound in the production of these resins has been bisphenol A (BPA). However, due to its proven toxicity, one of the biggest challenges has been replacing BPA with renewable and non-toxic phenols. In this sense, novel epoxy coatings were prepared from the direct valorization of the cashew nutshell liquid (CNSL) as alternatives anticorrosive coatings for steel. The epoxy resin was obtained by epoxidation of double bonds in the aliphatic chain of cardanol and cardol using in situ performic acid generated by a solvent-free methodology. The chemical structure of the resin was evaluated by spectroscopic techniques such as FTIR and 1H and 13C NMR. For the coatings preparation, epoxidized-CNSL (e-CNSL) resin was cured with different curing agents (DETA, IPDA and PFDA) and the resultant thermosettings were analyzed regarding their chemical, thermal, mechanical and anticorrosive properties using the DGEBA/IPDA coating as reference. The anticorrosive properties of the coatings were evaluated by electrochemical impedance spectroscopy. The results showed that e-CNSL-based coatings have great potential as bio-based coatings for corrosion protection, being an interesting alternative to replace the current BPA-based materials.