Abdulhakeem Bello, Odette Ngasoh Fayen, Abdulhakeem Bello, Joseph Emmanuel, Emmanuel Onche and Eddy Nnabuk Okon
Keywords: Corrosion, inhibition, electrochemical, gravimetric, adsorption, mild steel, synergism and soursop
Abstract:
<p class="western" align="justify" style="margin-bottom: 0in; direction: ltr; color: rgb(0, 0, 0); line-height: 32px; background: transparent; font-family: "Liberation Serif", serif; font-size: 12pt;"><i>Corrosion inhibition synergism between the molecules of leaves extract of soursop (LESS) and iodide ions on mild steel in an aggressive medium of 1M HCl was investigated through the employment of electrochemical, gravimetric and functional group techniques. The optimum inhibition efficiency (</i><i>η</i><i>%) of the extract was 88.54% but was synergistically improved to an optimum value of 95.69% at extract and iodide concentrations of 1000 ppm and 2.5 mM of LESS and KI respectively at 303 K. The adsorption profile of the joint extract and iodide aligned favourably with the Langmuir adsorption model with Langmuir adsorption parameter (k</i><sub><i>ads</i></sub><i>), having average values of 378.79 and 68.52 kJ/mol for LESS and LESS+KI respectively. However, thermodynamic considerations indicated that the adsorption process was spontaneous and favoured the physical adsorption mechanism because the free energy of adsorption (</i><i>Δ</i><i>G</i><sub><i>ads</i></sub><i>) was negative and was within the limit that supports charged transfer from the charged inhibitor to the charged metal surface. The negative values obtained from enthalpy change (</i><i>Δ</i><i>H) also confirmed that the adsorption is exothermic. Based on the observed pattern for the Tafel anodic and cathodic curves, convincing evidence supported that the inhibitor is a mixed type while the consideration of the diameter of the Nyquist plots strengthened by the calculated values of synergism parameters confirmed the significance of the inhibition and enhancement through synergism.</i></p><p class="western" align="justify" style="margin-bottom: 0in; direction: ltr; color: rgb(0, 0, 0); line-height: 32px; background: transparent; font-family: "Liberation Serif", serif; font-size: 12pt;"><br></p>
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