Resumo:
Metal corrosion is a critical industrial challenge, associated with high costs and environmental impact, especially in sectors that use carbon steel in aggressive environments. In this context, organic compounds of natural origin have been investigated as corrosion inhibitors, due to their adsorption capacity on metallic surfaces, associated with the presence of fatty acids and other bioactive compounds. Thus, this study investigated the potential of oil extracted from insects (Zophobas atratus larvae), a biodegradable source rich in unsaturated fatty acids and antioxidants, as a natural corrosion inhibitor for carbon steel. The oil was obtained by cold pressing and characterized for its fatty acid profile by gas chromatography with flame ionization detection (GC-FID), in addition to analyses by thermogravimetry (TG), differential scanning calorimetry (DSC), quantification of β-carotene and determination of density and viscosity as a function of temperature. Immersion tests in an acidic medium (HCl) were performed on SAE 1020 carbon steel, with the addition of oil to the corrosive medium, at different temperatures (23, 40, 60, and 80 °C) and exposure times (8 days – 192 h, 16 days – 384 h, and 24 days – 576 h). The oil presented a composition rich in bioactive compounds, with a high percentage of unsaturated fatty acids (~56%), especially linoleic (39.6%) and oleic (28.2%) acids, in addition to 5.34 mg/100 g of β-carotene. Thermal stability was observed up to approximately 200 °C, while viscosity and density decreased with increasing temperature. These properties contributed to an inhibitory efficiency of approximately 97% (23 °C – 8 days – 192 h) and 41% (80 °C – 8 days – 192 h). The results indicate the potential of Z. atratus oil as a technical alternative in the anti-corrosion protection of metals, based on its efficiency as a natural corrosion inhibitor.
