Improvement of anti-swelling property and anticorrosion performance of epoxy coatings by the introduction of nanocrystalline cellulose composite

In this work, the effect of nanocrystalline cellulose (NCC) as a nanofiller on the corrosion protection of epoxy resin coatings was examined. To solve problems like poor solvent swelling resistance and micropore formation during the solidification and shrinkage of epoxy resin coatings, NCC was modified with a silane coupling agent. Alkyl chains and active amine groups were grafted onto its surface, improving the dispersibility of NCC in organic solvents and its bonding with epoxy resin. In this study, NCC was modified by hexadecyltrimethoxysilane (HDTMS) and 3-aminopropyltrimethoxysilane (APTMS), and the modified NCC (M-NCC) was added to epoxy resin E-44 through dip-coating and spraying to prepare M-NCC/EP coatings. The experiments showed that more modified NCC significantly enhanced the solvent resistance of the coatings, reducing swelling and peeling in ethyl acetate and N, N-dimethylformamide (DMF). The impedance changes of different M-NCC/EP coatings after hot/cold cycles in 3.5% NaCl solution and air were monitored by electrochemical impedance spectroscopy. It was found that at 1% and 3% modified NCC doping, the impedance remained high after 60 hot/cold cycles in sodium chloride solution and air, indicating excellent protection for carbon steel. The low thermal expansion coefficient of NCC and its bond with epoxy resin reduced the internal stress during hot/cold cycles. Also, the hydrophobicity of the coating and the filled M-NCC blocked the invasion of corrosive media. This study offers new ideas and methods for making high-performance metal protective coatings and has significant application value.