Assessment of anti-corrosion potentials of extract of Ficus asperifolia -Miq (Moraceae) on mild steel in acidic medium

Abstract

The inhibitory potentials of ethanolic extracts and four fractions of the stem bark of Ficus asperifoliaMiq. for the corrosion of mild steel were assessed using weight loss method, Fourier atomic absorption spectroscopy, scanning electron microscopy (SEM). The effects of varying immersion period, concentration of the inhibitors and temperatures for mild steel corrosion in 5 M HCl acid solution were carried out. A detailed kinetic reaction, thermodynamic (Ea, ∆H, ∆S) and adsorption isotherm studies were obtained. The crude extract of F. asperifolia (EFA) has the highest inhibition efficiency of 55%. The inhibitory efficiency of the four fractions of F. asperifolia (EFA) compared with the crude extract was in the order ethyl acetate > n-hexane > butanol > EFA > Aqueous. The inhibition efficiency was found to increase with increase in the extracts concentration but decreased with temperature. Corrosion rate increases with time but decreases with extracts concentration. The kinetic studies of the data followed a first order reaction. Thermodynamic studies revealed that corrosion inhibition may be due to spontaneous mixed adsorption of the plant constituents on the metal surface. Experimental data were fitted to Langmuir, Freundlich and Temkin adsorption isotherms. The plant investigated showed a good potential for green corrosion inhibitors. Investigation of phytochemical constituents showed that the extracts contain alkaloids, flavonoids, saponins, tannins anthraquinones and reducing sugars.

Evaluation of the corrosion inhibition potentials of green-tip forest lily (<i>Clivia nobilis</i>) <i>leaves extract</i> on mild steel in acid media

“…The results obtained from weight loss (∆W), were used to compute the rate of Corrosion (C R ), Degree of surface coverage (D S ) and Inhibition efficiency (I.E) using equations 1, 2 and 3 respectively (Obiukwu et al, 2015 andFadare et al, 2016). …”

“…The design of the present study did not include phytochemical screening of Clivia nobilis leaves extract. Nevertheless, the presence of secondary metabolites such as alkaloids, tannins, saponnins and anthraquinones, in plants extracts, containing heteroatoms and .-electrons, have been identified to be responsible for corrosion inhibitory properties on metal surface (Fadare et al, 2016). Phytochemical analysis will also identify and explain the greater inhibitive properties of HCl over that of H 2 SO 4 .…”

“…In recent times, corrosion inhibitors of natural origin are now being preferred as they are ecofriendly, biodegradable and possess no threat to the environment (Ugi and Ageng, 2013;Devi and Rajendran, 2011;Okafor et al, 2007;Oguze, 2001). Several studies on the use of plant extracts for the inhibition of corrosion of mild steel have been reported (Nnenna et al, 2011;Patel et al, 2013;Obiokwu et al, 2015;Gusti et al, 2015;Fadare et al, 2016). Many of these authors have attributed inhibition to adsorption mechanism.…”

“…This suggests that the corrosion of mild steel is much more difficult with Clivia nobilis and the interaction of the inhibitor extract with mild steel surface was more of physical process than chemical. Conversely, a decrease in Activation energy with increasing inhibitor concentration would have implied enhancement of corrosion and a chemisorption mechanism (Fadare et al, 2016). Gasometric Studies: The rates of the anodic and cathodic reactions must be equivalent, being determined by the flow of current from anode to cathode (Negm et al, 2013).…”

On the use of factorial experiments for optimizing inhibition effect of acid extract of Gnetum Africana on copper corrosion

“…These advantages are the reasons for the use of extracts of plants and their products as corrosion inhibitors for metals and alloys under different environments (Patni et al, 2013). Among natural plants extract as corrosion inhibition of mild steel and aluminum alloy in acidic medium are extracts from Ficus asperifolia (Fadare et al, 2016) and Newbouldia leavis (Lebe et al, 2011). Similarly, the inhibiting effect of Chenopodium extract against the copper corrosion in 1 M HNO 3 was studied by weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and electrochemical frequency modulation (EFM) techniques (Motawea, 2019).…”