Electrochemical and Adsorption Studies of Siam Leaf Extract’s Effect on Mild Steel Corrosion Inhibition in Sulphuric Acid Medium

In a 1.5 M H₂SO₄ environment, the study explores the efficacy of Siam leaf extract (SLE) as a corrosion inhibitor for mild steel, looking for eco-friendly alternatives to inorganic inhibitors. SLE concentrations ranging from 2.0 to 10.0 g/L were studied using various methods, including potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM). Phytochemical and Fourier transformation infrared (FTIR) analyses were used to identify the bioactive constituents and functional groups contained in the extract. The results indicated an increase in the efficiency of inhibition associated with higher concentrations of the inhibitor, with maximum efficiencies of 93.91% (PDP) and 86.58% (EIS) at a concentration of 10 g/L. Of the four isotherm models used, the Langmuir model best fits the adsorption kinetics of the inhibitor. Electrochemical analyses indicated that the Siam leaf extract shows high inhibition efficiency and functions like a mixed-type inhibitor. The protective adherence of extract molecules to the mild steel surface was validated by SEM examination, consistent with the findings of PDP and EIS.