Browsing by Author "Ohaegbulam, Chinyere Elizabeth"

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    Corrosion inhibition of mild steel using landolphia heudelotii and ocimum gratissimum in acidic media
    (Federal University of Technology, Owerri, 2016-12) Ohaegbulam, Chinyere Elizabeth
    The corrosion inhibition performance of water extracts of Landolphia heudelotii and Ocimum gratissimum on mild steel in 1 M HCl and 0.5 M H2SO4 was investigated using weight loss and potentiodynamic polarization technique on mild steel. Results from weight loss analysis revealed that inhibition efficiency increased with increase in concentration of the inhibitors while corrosion rate decreased with increase in concentration of the inhibitors due to the adsorption of the organic molecules on the metal surface. Highest inhibition efficiency of 97.27% and 94.31% was recorded in Ocimum gratissimum and Landolphia heudelotii at 2500mg/l in 1M HCl after twelve days respectively. Temperature studies also revealed the inhibition efficiencies of both extract at the temperature ranges of 313 K - 333 K, highest inhibition efficiency of 97.60% and 95.84% was recorded in Ocimum gratissimum and Landolphia heudelotii in 1 M HCl respectively at 323 K and 2500 Mg/l. From the values of activation energy obtained, the mechanism of the adsorption process was proposed to be predominantly of physisorption in both plant extracts. The values of ΔG obtained reveals spontaneity of the process while ΔHads reveals endothermic and exothermic reactions occurring in 0.5 M H2SO4 and 1 M HCl in both plant extracts respectively. Potentiodynamic polarization results showed that both the anodic and cathodic reactions were inhibited indicating that the inhibitors are of mixed type. The experimental data obtained fits well with Langmuir adsorption isotherm indicating that the inhibitors were adsorbed uniformly on the metal surface. The mechanism of adsorption was proposed to be as a result of the bonding of the free electrons of the inhibitor with the metal surface due to electrostatic force of attraction existing between inhibiting organic ions and the electrically charged metal surface at the metal/solution interphase.