Avaliação cíclica eletroquímica acelerada de revestimentos inteligentes com microcápsulas de uréia-formaldeído com núcleo contendo agentes de autorreparo

Abstract

Metal corrosion causes major economic losses, accounting for up to 3% of GDP. Techniques such as coatings and chemical inhibitors are used to control it, but these coatings can fail over time. Smart, self-healing coatings emerge as a promising solution, regenerating damage and restoring protection. The addition of microcapsules with active nuclei and corrosion inhibitors, such as imidazole, improves the effectiveness of these coatings, making them more resistant to failure and increasing their durability. Therefore, this study develops an intelligent self-healing coating with epoxy resin, microcapsules with urea-formaldehyde wall and active epoxy core, silicon alkoxide precursor and imidazole applied on phosphatized carbon steel. The method of synthesis of microcapsules was selected according to morphology among those evaluated in this work, and then the microcapsules were produced and had their chemical composition evaluated and confirmed through Fourier transform infrared spectroscopy (FTIR) analysis. The scanning electron microscopy technique with field emission source (SEM-FEG) evaluated the morphology of the microcapsules and their mean diameters, which were 4.15 µm, 3.17 µm, 2.56 µm, and 2.18 µm for MEp, MEpIM, MSi, and MSiIM respectively. In the electrochemical tests The Ep0 sample, composed only of epoxy resin, had the lowest impedance modulus and phase angle compared to other samples produced. Samples containing microcapsules showed better anticorrosive and self-repair performance throughout the ACT cycles. The impedance values in the sixth cycle were for EpMEp15, EpMEpIm15, MSi15 and MSiIM15 were |z|0.01= 17960 (ômega).cm², |z|0.01= 1580 (ômega).cm² , |z|0.01= 3860 (ômega).cm² and |z|0.01= 929 (ômega).cm², respectively, surpassing the standard epoxy resin coating (|z|0.01= 506 (ômega).cm²). Compared to samples containing only epoxy resin and silicon alkoxide precursor, samples with imidazole active core reduced the electrochemical performance of the self-repair system. The hardness test indicates an increase in the hardness of the coating with the addition of microcapsules, going from H to 2H compared to pure epoxy resin. The direct and reverse impact tests revealed fragility of the coatings containing microcapsules compared to pure epoxy resin, presenting cracks and detachment. However, the addition of microcapsules did not affect the adhesion to the metal substrate. Salt spray tests confirmed that the microcapsules improved corrosion resistance compared to pure epoxy resin. The results allowed us to conclude that the use of a self-repair system with microcapsules with an active nucleus of epoxy, precursor silicon alkoxide and imidazole are promising, ensuring greater protection against corrosion of epoxy resin on carbon steel, even after the insertion of a cut exposing the substrate. [resumo fornecido pelo autor]