Abstract
The corrosion inhibition potential of alkaloids from Kopsia terengganensis bark extract (KTBE) in mitigating the mild steel corrosion in a CO2-saturated 3.5% NaCl medium was evaluated. Standard corrosion evaluation methods, including weight loss test, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization (PD) were employed, which revealing a concentration-dependent enhancement in KTBE's inhibition efficiency. At 500 ppm, the corrosion inhibition efficiency recorded the highest value of 90.63% based on the weight loss study and 87.38% based on electrochemical analysis. Tafel slopes in PD studies affirmed that KTBE functioned as an anodic-type inhibitor. The adsorption of the inhibitor is in accordance with the Langmuir adsorption isotherm with an adsorption free energy (ΔG°ads) of −26.47 kJ/mol, suggesting the binding of KTBE molecules by means of physisorption. Surface analysis conducted through scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, and Fourier transform infrared spectroscopy (FTIR) confirmed the formation of a protective inhibitive layer on the surface of mild steel. The proposed corrosion inhibition mechanism involves electrostatic interactions between KTBE molecules and the mild steel surface. This comprehensive investigation underscores KTBE's potential as an effective corrosion inhibitor in corrosive environments.
Published Version
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