Electrochemical Investigation of the Anti-corrosive Effect of Spondias mombin Leaves Extract on the Corrosion of Aluminium Alloy (AA2024) and Mild Steel in 0.5 M NaCl

The inhibiting effect of Spondias mombin (SM) leaves extract on the corrosion of AA2024 and mild steel in 0.5 M NaCl environment was investigated using electrochemical techniques. Tafel plots obtained from the potentiodynamic polarization (PDP) experiments indicate that for both metals, the curves shifted toward more negative values of the corrosion current density (Icorr) as the inhibitor concentration increased. More so, for all concentrations of the inhibitor, the values of maximum displacement shift in corrosion potential (Ecorr) were found to be less than 85 mV. This shows that SM behaves like a mixed-type corrosion inhibitor. The electrochemical impedance spectroscopy (EIS) study shows that for both metals, the charge transfer resistance (Rct) values increased with an increase in concentration of the inhibitor. The increase in values of Rct can be attributed to the formation of protective film at the metal-solution interface. The Nyquist plots show semi circles whose diameter increased as the inhibitor concentration is increased and this is suggestive of retardation in corrosion process. The inhibition efficiency values obtained in the EIS experiment were found to be in close conformity with those of the PDP experiment.