Fig and olive leaf extracts as eco-friendly corrosion inhibitors for copper in hydrochloric acid solutions

Abstract

This study investigates the effectiveness of olive leaf extract (OLE) and fig leaf extract (FLE) as environmentally friendly corrosion inhibitors for copper in hydrochloric acid (HCl) solutions, emphasizing their potential as sustainable alternatives to synthetic inhibitors. Corrosion inhibition was evaluated across inhibitor concentrations ranging from 0.25 to 1 g/L in 0.5 to 2 M HCl solutions. Results demonstrated that both OLE and FLE significantly suppressed copper corrosion, with FLE exhibiting superior inhibition performance. The inhibition efficiency increased with increasing inhibitor concentration, peaking at 69% for FLE and 47% for OLE in 0.5 M HCl at 0.75 g/L and 25 °C. However, efficiency declined as the acid concentration increased, highlighting the sensitivity of the inhibitors to acidic conditions. Additionally, solution flow rate played a crucial role in inhibition efficiency, with a peak efficiency of 62% for FLE and 57% for OLE at 18.98 L/min, suggesting enhanced mass transport effects. Adsorption studies confirmed that both inhibitors followed the Freundlich isotherm, suggesting multilayer adsorption and secondary interactions, such as hydrogen bonding and van der Waals forces, contribute to the stabilization of the inhibitor layers on the metal surface. The findings highlight the potential of plant-based extracts as cost-effective and sustainable corrosion inhibitors, with practical implications for industrial applications such as pipeline maintenance and acid cleaning processes.