Influence of Bauhinia tomentosa Stem Bark Extract on the Electrochemical Behavior of Low-Carbon Steel in 1 M HCl

Plant-derived extracts serve as effective environmentally friendly inhibitors of corrosion because they are biodegradable, innocuous, and derived from renewable resources, rendering them a more friendly and sustainable substitute for harmful synthetic inhibitors. In this study, the inhibitive performance of Bauhinia tomentosa (BT) stem bark extract on low-carbon steel (L-CS) deterioration in 1 M hydrochloric acid was assessed via open circuit potential (OCP), potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), and gas chromatography–mass spectrometry (GC–MS). The results show that BT extract suppressed L-CS corrosion, with inhibition efficiency improving as inhibitor concentration increases. Polarization data indicate that BT functions as a mixed-type inhibitor by simultaneously retarding anodic metal deterioration and cathodic hydrogen liberation reactions. Corrosion current density (Icorr) noticeably reduced from 1241 μAcm-2 (in the absence BT) to 687 μAcm-2 (in the presence of 1000 ppm of BT). Impedance measurements revealed improved resistance associated with charge transfer (Rct), confirming adsorption of BT molecules on the L-CS exterior. Rct increased from 3533  cm2 (without BT) to 4794  cm2 (when 1000 ppm of BT was introduced). GC–MS analysis identified organic compounds containing heteroatoms and pi-electron schemes, which enable robust interaction with the metal surface. An inhibition efficiency of up to 45% was achieved at 1000 ppm BT from PDP analysis, highlighting the prospect of BT extract as a corrosion inhibitor with modest performance in acidic environments.