Browsing by Author "Emmanuel, Jovine"

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    Synergistic effects of halide ions on the corrosion inhibition of mild steel by acacia Senegal gum in sulphuric acid solution
    (University of Dar es Salaam, 2011) Emmanuel, Jovine
    This work was aimed at investigating the inhibitive effect of naturally occurring gum exudate from Acacia senegal on the corrosion of mild steel in sulphuric acid in the temperature range 35 oC-70 oC. Electrochemical impedance spectroscopy and potentiodynamic polarization techniques were used in this investigation. The results reveal that the gum exudate reduces the corrosion rate of mild steel in sulphuric acid solution. The inhibition efficiency was found to increase with increase in gum exudate concentrations up to 300 ppm, reaching 43.3 % at 35 oC and decreased with increasing temperature up to 70 oC. Addition of halide ions to the gum exudate solution enhanced the inhibition efficiency up to 81.6 % at 35 oC because of synergistic effect. The enhancement effect of the halides was higher with iodide ions than with bromide ions. The synergism parameter, S1, evaluated was found to be greater than unity. The adsorption of Acacia senegal gum on the mild steel surface in the presence of sulphuric acid obeyed Langmuir’s adsorption isotherm. Temperature was observed to have adverse effect on the synergistic effect of halide ions as the enhancement effect decreased with increase in temperature. The presence of the gum exudate in test solutions increased the activation energy (Ea). A physical adsorption mechanism is proposed based on the apparent activation energy obtained. The corrosion rates of mild steel, inhibition efficiencies of the gum exudate and the synergistic effects of halides obtained from polarization and impedance measurements were in good agreement.