Assessment of Piper siriboa L. (Buyo) leaf extract as a green corrosion inhibitor for carbon steel in hydrochloric acid

Corrosion of carbon steel in acidic environments remains a major challenge for infrastructure and industrial systems, leading to material degradation and increased maintenance costs. Although synthetic corrosion inhibitors are widely used, their environmental drawbacks have driven interest in plant-based alternatives. This study investigates the potential of Piper siriboa L. (Buyo) leaf extract as a green corrosion inhibitor for carbon steel in an acidic environment. The leaf extract, obtained through ethanol maceration and characterized using Fourier Transform Infrared (FTIR) spectroscopy, confirmed the presence of corrosion-inhibiting functional groups. Corrosion performance was evaluated using the weight-loss method over 15 days at extract concentrations of 1–5% (v/v) in 1.0 M HCl, with the 5% extract achieving the highest inhibition efficiency (87.78%) and consistently outperforming lower concentrations. Nonlinear regression indicated that the inhibition followed the Freundlich isotherm model (R2 = 0.9912), suggesting favorable multilayer physisorption on heterogeneous steel surfaces. SEM analysis further revealed that treated steel samples developed a protective film and exhibited reduced surface damage compared to untreated samples. Overall, the findings establish P. siriboa L. leaf extract as a promising and environmentally sustainable corrosion inhibitor, warranting further investigation of its long-term performance and broader applicability.