Vol. 3, Issue 1 (2019)
Management of aqueous corrosion of federated mild steel (Local constructional steel) at elevated temperatures employing environmentally friendly inhibitors: Matricaria chamomilla plant
Author(s): Ugi BU, Abeng FE, Enang HE, Obeten ME, Uwah IE
Abstract: Management of aqueous corrosion of federated mild steel at elevated temperatures employing environmentally friendly inhibitors of Matricaria chamomilla plant was carried out at temperatures of 318 K, 333 K and 347 K in 0.5 M H2SO4 solution. Thermometric, potentio-dynamic polarization and electrochemical impedance spectroscopic measurements were adopted for the study. In all, both inhibitors demonstrated an appreciable result at the tested temperatures with the alkaloid extract of Matricaria chamomilla plant (AEMCP) showing a better inhibition of 99 % compared to Non alkaloid extract of Matricaria chamomilla plant (NAEMCP) 95 %, implying that the hetero-compounds in the alkaloid inhibitor has a stronger adsorption compared to non alkaloids. The values of the charge transfer resistance are seen to be increasing with increasing concentration of both inhibitors which reveals the strong adsorption of the inhibitors on the metal surface. The lower corrosion current density (Icorr) values in the presence of inhibitors without causing significant changes in corrosion potential (Ecorr) suggested a mixed type inhibitor for both extracts. The ∆Hads results obtained indicated that the inhibition reaction is endothermic which suggested that they inhibitors adsorbed heat from the surrounding to form more and stronger bonds with the mild steel. Meanwhile, values of ∆Sads were negative indicating the absence of disorderliness. Hence, there was association of the inhibitor molecules. The ∆Gads values followed a physical adsorption process as values are below – 20 kJ/mol and the negative values indicated a more stabled and spontaneous reaction process. The reaction obeyed the Frunkim and El-Awady adsorption isotherms as their correlation coefficient was 0.99, an indication that the data fit the isotherms.