Pyrolysis of Syagrus coronata: Transforming agroindustrial waste into a new environmentally sustainable corrosion inhibitor

For the first time, a pyroligneous acid was used as a corrosion inhibitor. It was obtained from the pyrolysis at 400 °C of the Syagrus coronata's fruit (also known as licuri) waste with more than 30% yield. Gas chromatography–mass spectrometry analysis was performed and more than 70 substances were identified (phenolics, furanics, lactones, nitrogenated, among others). This aqueous phase of licuri's pericarp pyrolysis (APLic) was evaluated as an unprecedented and original corrosion inhibitor for 1020 mild steel in acid media (HCl 1 mol L−1). Gravimetric and electrochemical methods showed that APLic reached 91% anticorrosive efficiency at 0.6 g L−1. UV–Vis Spectroscopy showed that the concentration of organic molecules in the solution decreases after 5 h of immersion and infrared spectroscopy showed the interaction between the organic molecules with the mild steel surface. Surface characterization with Atomic Force Microscopy and Scanning Electron Microscopy indicated the formation of a protective film on the metal surface. All results indicated the adsorption on the mild steel surface and formation of a protective barrier that prevents the corrosion process.