DOI: https://doi.org/10.55373/mjchem.v27i3.100

Keywords: Corrosion; inhibition efficiency; immersion test; potentiodynamic polarization; electrochemical impedance spectroscopy

Abstract

Harumanis mango peel extract contains phenolic compounds such as flavonoids and antioxidants, making it a potential green organic corrosion inhibitor to replace harmful traditional chemicals. This study focuses on developing a green corrosion inhibitor for mild steel in near-neutral environments, using plant extracts from local Harumanis mango peels. The effectiveness of the inhibitors was evaluated through several types of corrosion assessment; weight loss test (WL), potentiodynamic polarisation (PP), electrochemical impedance spectroscopy (EIS), optical microscope and scanning electron microscopy (SEM). Sodium chloride (0.6 M NaCl) was used as the corrosive medium for the immersion at 30 to 60 ⁰C without and with 50 to 350 ppm inhibitor. The highest inhibition efficiency obtained for WL, PP, and EIS was at 250 ppm, which is 86%, 84%, and 90%, respectively. Analysis via Tafel plot in polarisation study exhibits a decline in corrosion current density after the addition of inhibitor indicating the corrosion inhibition. The polarization study also shows the Harumanis mango peel extract acts as a mixed-type inhibitor. The increase in Rct values signifies lower corrosion rates and, thus, higher inhibition efficiency, as analyzed from the Nyquist plot in the EIS study. The surface morphology of the mild steel shows a reduction in corrosion impact after being treated with the inhibitor. From the microscopy analysis, the mild steel surface displays the appearance of minimum and smaller pits with the addition of the inhibitor compared with the mild steel surface in the 0.6 M NaCl. The adsorption of the Harumanis mango peel corrosion inhibitors obey the Langmuir isotherm model.