Electrochemical Corrosion Inhibition Process, Adsorption Mechanism and Mechanical Effect of Newbouldia laevis Leaf Extract on Aluminum Alloy in Acidic Environment

Aims: This research is aimed at using advanced corrosion identification and corrosion inhibition technique to investigate the corrosion inhibition mechanism of Al Alloy (AA5052) in 1.0 M HCl solution using Newboudia laevis leaf extract.

Place and Duration of Study: The research was carried out at Material Science Laboratory Group, Physics/Electronic Department, Abia State Polytechnic, Aba Abia State.

Methodology: Extraction of the green leaf was done with reflux apparatus under constant temperature. The 100% inhibitor solvent was diluted to the various inhibitor concentrations. Gravimetric technique and electrochemical impedance spectroscopy (EIS) were employed to study the corrosion and corrosion inhibitory behavior of the metal in the various environments. Scanning Electron Microscope and OPTICAL emission microscopy were used to investigate the surface structure of the corroded and inhibited metal alloy. The influence of the leaf extract on the mechanical hardness of the Al alloy AA5052 was tested using Vickers indentation hardness test.

Results: The presence of the Newbouldia leavis leaf extract significantly reduced the weight loss and also decreased the rate of chemical attack on the AA5052 alloy. The inhibition efficiency of the inhibitor increases with increase in concentration but decreased with increase in temperature. The introduction of the leaf extract alters the electrochemical behaviours of the metal in the acidic environment. The inhibitor mechanism was found to be through adsorption on the metal surface according to Langmuir adsorption isotherm. The Gibb’s free energy confirms that the inhibition of the leaf to corrosion attacks is spontaneous. The calculated activation energy, heat of adsorption, enthalpy and the entropy implications of the leaf extract were appraised. The surface morphology of the metal was studied to ascertain the level of redemption offered by the green inhibitor molecules to the material degradation. Vickers hardness test revealed that the presence of the inhibitor improved the mechanical hardness of the corroded Al alloy.

Conclusion: The acidic corrosion of AA5052 has been studied. The study shows that Newboudia laevis extract can be used to combat the corrosion attacks on AA5052 alloy.