Corrosion inhibition of carbon steel using insect oil: Chemical characterization and long-term performance

The pursuit of eco-friendly corrosion inhibitors has motivated the exploration of alternative biomaterials with low environmental impact. This study presents the first report on oil extracted from Zophobas atratus larvae (INOLZ) as a natural corrosion inhibitor for SAE 1020 carbon steel in acidic media. The oil, obtained by cold pressing, was characterized in terms of its fatty acid profile, physicochemical properties, thermal stability, and β-carotene content. Compositional analysis revealed a high content of unsaturated fatty acids (57.50%), predominantly oleic (31.4%) and linoleic (24.8%) acids, alongside 5.24 mg/100 g of β-carotene, all of which are known for their adsorption and antioxidant capabilities. Thermogravimetric analysis confirmed thermal stability up to 200 °C, and immersion tests in 1 mol·L − 1 HCl yielded inhibition efficiencies as high as 97.2% at 23 °C after 8 days of exposure. However, performance declined as temperature and exposure time increased, falling to 20.7% at 80 °C after 24 days. Microscopy revealed reduced surface degradation in treated specimens, confirming the protective action of INOLZ. The findings indicate that Z. atratus oil forms a lipid film that suppresses corrosion through combined barrier and antioxidant mechanisms. This biobased inhibitor offers a promising sustainable alternative to conventional synthetic inhibitors, in line with green chemistry principles and circular economy strategies. Further work is required to enhance its thermal resistance and long-term performance.