Abstract
The corrosion and corrosion inhibition of mild steel in 1.0 M H2SO4 containing 10% ethyl alcohol(EtOH) by Zizyphus Spina-Christi (ZSC) extracts (aqueous extract and alcoholic extract) has been studied using chemical techniques( hydrogen evolution(HE) and mass loss(ML)) and electrochemical techniques(electrochemical impedance spectroscopy(EIS) and potentiodynamic polarization(PDP)). The effect of acid concentration on the corrosion rate of mild steel increases with acid concentration (0.25-1.5) M showing first order corrosion reaction without changing the reaction mechanism, and the results showed that when the concentration of ZSC extracts (aqueous extract and alcoholic extract) increased the rate of steel corrosion is decreased, which indicates that the inhibition of the corrosion process is produced. Electrochemical impedance spectroscopy results showed that the corrosion and corrosion inhibition of steel occurred mainly by charge transfer. The electrochemical results of polarization also showed that the extracts of ZSC plant act as mixed type inhibitors, they retarded both cathodic and anodic reaction. The experimental results from chemical and electrochemical studies were fit Langmuir isotherm. Values of equilibrium constant of adsorption Kads and the standard free energy of adsorption o . ads
Highlights
C inhibitor can be chosen from compounds that have hetero atoms in their aromatic ring system or synthesized from cheap raw materials (Chetounani et al, 2004; Bouyanzer and Hammouti,2004; Ebenso et al.,2004; Bendahou et al, 2006; Eddy, 2008)
The influence of H2SO4+10%EtOH concentrations (0.25M, 0.5M, 1.0M and 1.5M) on mild steel corrosion at 300 C is shown in Figure (2)
The rates of corrosion from Hydrogen evolution (HE) and ML methods (R & R) are recorded in Table (2), it is found that the rates of corrosion increases with increasing acid concentration, this indicates that steel corrosion in H2SO4 is concentration dependent
Summary
C inhibitor can be chosen from compounds that have hetero atoms in their aromatic ring system or synthesized from cheap raw materials (Chetounani et al, 2004; Bouyanzer and Hammouti,2004; Ebenso et al.,2004; Bendahou et al, 2006; Eddy, 2008). The successful use of naturally occurring substances to inhibit the corrosion of metals in acidic and alkaline environments has been reported by some research groups (El-Etre , 2003; Chetounani et al, 2004; El-Etre et al, 2005; Bendahou et al, 2006; El-Etre, 2006; Ebenso et al, 2008; *Eddy et al, 2008; **Eddy et al, 2008; ***Eddy et al, 2008; Odoemela and ****Eddy, 2008; Ebenso et al, 2009). The use of aqueous extract and alcoholic extract of Zizyphus Spina-Christi (ZSC) plant as a green inhibitor has not been reported elsewhere. The objective of the present study is aimed at investigating inhibitive and adsorption properties of aqueous and alcoholic extracts of Zizyphus Spina-Christi leaves for the corrosion of mild steel in H2SO4. All reagents used (H2SO4 and KCl) for the study were analar grade and deionized water was used for their preparation
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