Estudo de revestimentos orgânicos anticorrosivos à base de resina epóxi com a incorporação de microfibra de coco (Cocos nucifera L.)

Abstract

Organic coatings are the main method of metal protection against atmospheric corrosion due to their cost-effectiveness. Anticorrosive paint systems with epoxy resin have high efficiency, however, these materials are improved by the addition of organic and inorganic additives. Additives block surface microspore’s epoxy resin-based coatings. Combining the environmental issue of the reuse of an agricultural by-product, with the need for research and development of components for ecologically correct coatings, this work analyzes the feasibility of incorporating coconut microfiber, as a renewable pigment, in anticorrosive coatings based on epoxy resin. For incorporation in the epoxy system, the fiber was fragmented and sieved (MESH 250). To evaluate better incorporation in the epoxy system, the microfibers were submitted to alkaline treatment, with immersion in sodium hydroxide solution - NaOH 5% by mass - for 24 hours. The morphological characterization of untreated microfiber (FN) and treated microfiber (FT) was performed by laser diffraction and scanning electron microscopy (SEM). The FN and FT samples were analyzed by spectroscopy in the infrared region with Fourier transform (FTIR-ATR) and their thermal degradation by thermogravimetric analysis (TG/DG). In addition, the samples were characterized for density and oil absorption. To evaluate its effectiveness as an anticorrosive pigment, gravimetric mass loss tests and potentiodynamic polarization measurements were performed. After fiber incorporation, the coatings were evaluated using the electrochemical impedance spectroscopy (EIS) technique. Despite the high oil absorption of the samples (FN-95.73, FT-99.46), they showed low density, resulting in CPVC values that allow the formulation of coatings with ideal PVC. The FTIR-ATR results showed that the untreated microfiber samples have a lignocellulosic matrix and tannins in their composition, on the other hand, the removal of some materials from the structure in the treated sample was identified, increasing the concentration of lignin in its structure. The results of the mass loss tests and the potentiodynamic polarization curves showed an inhibition efficiency of approximately 70% for FN and 90% for FT. The coatings in which the untreated microfiber was incorporated showed higher values of impedance modules at low frequencies (LF) than the other samples. Through the present study, it was possible to verify that coconut microfibers have potential use as an anticorrosive green pigment for the epoxy system.