Retarding Mild Steel Corrosion using a Blend of Schiff Base Metal Complex and Neem Plant Extract

Abstract

Prepared inhibitor blend of synthesized Co (II) Schiff base complex and Azadirachta indica extract was applied as anti-corrosion agent to mild steel in acidic (0.5 M H2SO4) medium. A synergistic performance was the lookout
of the study, with the green inhibitor as the synergistic additive. Inhibitors are characterized by their active functional groups, UV-visible profile and bioactive compounds. Surface characteristics of polished, corroded and coated mild steels were investigated using weight loss experiments. Results of phytochemical screening shows the presence of possible bioactive species, including glycoside, tannins and phenolic compounds, saponin, Steroids and Triterpenoids. Weight loss experiments at temperature range of 303 K to 323 K were performed. Inhibition efficiencies of the three systems demonstrated increments with increasing inhibitor concentration and decreases as the temperature rises, thus characterizes physi-sorption mechanism. The ethanol extract of Azadirachta indica leaves, cobalt (II) Schiff base complex and the blend in 0.5 M H2SO4 gives up to 46.88 %, 31.16 % and 59.69% inhibition efficiencies respectively at 323 K. The adsorption equilibrium data of these inhibitors on the surface of mild steel fits the Freundlich, Langmuir and Dubinin - Raduskevich isotherms at varying extent and the values of ΔGads for all the isotherms were below 20 kJ/mol, suggesting physical adsorption. The estimated thermodynamic parameters support process spontaneity. Generally, enhanced performance of blend inhibitor showed a synergistic effect (S1> unity) and proved the effectiveness of derived blend as potent inhibitor of mild steel corrosion in acidic medium.

Keywords: Antagonistic, Blend, Complex, Inhibitor, Synergistic