POLY(PROPENONITRILE) AS ANTI-CORROSIVE AGENT FOR MILD STEEL IN 0.1M HYDROCHLORIC ACID SOLUTION: EXPERIMENTAL, DFT AND MOLECULAR DYNAMIC SIMULATION STUDIES

Abstract

The anticorrosion studies of poly(propenonitrile) (PPN) on mild steel in acidic media was carried out in 0.1 M HCl using gasometric, gravimetric, and electrochemical techniques at room temperature and at elevated temperatures (303, 313, 323 and 333 K). In all test settings, the inhibitory effectiveness changed in direct proportion to the PPN concentration and in inverse proportion to the exposure duration and temperature. The anticorrosion potential of PPN is attributed to the adsorption of its molecules on the metal surface, blocking the active corrosion sites on mild steel. The adsorption mechanism conformed to the Langmuir and Temkin adsorption isotherm models with the best fits recorded for the Langmuir model (R2 of 0.998). The thermodynamic parameters obtained; Gibbs free energy (?Go ads) as well as activation energy (Ea), all favored a spontaneous and exothermic physical adsorption reaction mechanism of PPN. Electrochemical impedance spectroscopy (EIS) obtained revealed increasing charge transfer resistance as PPN concentration increases. The DFT study, shows a significant value for electronegativity in both neutral (3.751 eV) and protonated (2.873 eV) states which indicates that PPN favors strong adsorption. MDs studies corroborated the strong adsorption and further revealed the inhibitor was more stable in its neutral form than in its protonated state, with energy differences of 6.507 eV and 4.961 eV, at 298 oC and 318 oC respectively. The results of the several test carried out were all fully connected to one another.