The trio of Jatropha curcas fruit seeds: A performance battle of three plant-based inhibitors

Jatropha curcas has been attracted much attention due to its superior biodiesel applications. Three novel bio-based inhibitors arisen from its fruit seed meal (JFM): refluxed extract (RJFME), ultrasound-assisted extract (UJFME) and carbon dots (CDs-JFM) are reported for the first time in retarding the corrosion of cold-rolled steel (CRS) in hydrochloric acid (HCl) medium, achieving the highest inhibition efficiencies of 96.5 %, 93.5 % and 96.2 % at 303 K with the addition of 100 mg L⁻¹, respectively. Their excellent performance depends on the spontaneous formation of protective film on CRS surface by Langmuir adsorption mode, which extremely impedes the diffusion of corrosive particles of Cl⁻, H₃O⁺ and H₂O. This results in a substantial reduction in corrosion current density and an increase in polarization resistance. Three JFM inhibitors exhibit comparable inhibition capacities in weight loss, electrochemical and surface examinations. CDs-JFM stands out as a more superior inhibitor due to its stable and long-lasting performance in highly corrosive HCl solution and over extended reaction time. Remarkably, the fluorescence properties of CDs-JFM act as a probe to elucidate its adsorption mechanism onto CRS surface. This work unveils the potential of JFM as a novel green inhibitor, developing the highly efficient utilization of Jatropha curcas.