Department of Chemical Engineering.

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    Thermodynamic and Adsorption Influence on the Corrosion Inhibitive Performance of Pawpaw Seed on A36 Mild Steel in 1 M H2SO4 Medium
    (2021) Ayoola, Ayodeji Ayodele; Fayomi, O. S. I.; Agboola, Oluranti; Durodola, B. M.; Adegbite, A. O.; Etoroma, A. A.
    This research work investigated the corrosion inhibitive performance of the nano-sized pawpaw seeds on A36 mild steel in 1 M H2SO4 medium. The metal samples were subjected to corrosive environment (with and without varied concentrations of the inhibitor) using both the weight loss and potentiodynamic polarization tests at different temperatures (278.15–318.15) K for weight loss and (30.15–323.15) K for potentiodynamic polarization study). The equipment used include Thermo scientific ARL OP-TIM’X 166 spectrometer (for metal composition analysis) and Autolab PGSTAT 302 N (for potentiodynamic polarization test). The results obtained showed that the nano-sized pawpaw seed is an effective organic inhibitor with optimum inhibitor concentration of 4 g/cm3 having inhibitor efficiency of 92% from the weight loss test. The inhibition performance of pawpaw seed increased with decrease in temperature for both the gravimetric tests (between 278.15 K and 318.15 K) and potentiodynamic polarization study (between 300.15 K and 323.15 K). The Langmuir adsorption isotherm with correlation coefficient (R2) of 0.99 accurately predicted the adsorption mechanism of the inhibitor on the metal surface. The thermodynamic change in Gibbs free energy (ΔGads) of (-12.9544 to -11.5409) kJ/mol and adsorption equilibrium constant ( Kads) of (1.70–2.99) of the adsorbed inhibitor on metal surface revealed both the spontaneous and physisorption nature of the inhibitor-adsorbed process. Also, the tafel plot showed that the inhibitor acted as a mixed-typed inhibitor.
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    Corrosion inhibitive effects of calcium-modified zinc phosphate coating on A36 mild steel
    (Results in Engineering, 2023) Ayoola, Ayodeji Ayodele; Durodola, B. M.; Bablola, R.; Adeniyi, O. D.; Ilobinso C. E.
    In this work, the corrosion inhibitive performance of calcium modified zinc phosphate coating on A36 mild steel was studied. Treated A36 mild steel samples were subjected to coating through immersion in phosphating bath containing varied concentrations of calcium oxide (0–2.5 g/L) at different operating temperatures (60–80 C) and immersion time (30–60 min). The coated samples were then subjected to corrosion tests (weight loss and inhibition efficiency determination) in 3.5% NaCl solution, to examine the anticorrosion behaviour of the coated mild steel in NaCl solution. The calcium modified phosphating process which was carried out at 80 ◦ ◦ C with calcium concentration of 2.5 g/L gave a better and more uniform coating on A36 mild steel surface, as confirmed by visual inspection and SEM/EDS analysis. Also, Freundlich adsorption isotherm was found suitable for the prediction of the adsorption of both calcium and zinc particles on A36 mild steel, as indicated by the coefficient of determination (R 2 ) values of approximately one. The adsorption of both the zinc and calcium particles on A36 mild steel was found to be spontaneous and physical process, as revealed by the values of K ads and ΔG ads .