Mitigation of corrosion in petroleum oil well/tubing steel using pyrimidines as efficient corrosion inhibitor: Experimental and theoretical investigation

Present investigation focused on to study the corrosion inhibition capabilities of pyrimidine derivatives; MPA [4,6-bis(4-methoxyphenyl) pyrimidin-2-amine] and CPA [4,6-bis(4-chlorophenyl) pyrimidin-2-amine] for oil well/tubing steel (N80 steel) in 15 % HCl solution. Corrosion inhibition efficiency of both inhibitors increases on increasing the concentration and decreases on increasing the temperature. The studied organic compounds show excellent corrosion mitigation properties with highest efficiency of 99.5 % for MPA and 94.7 % for CPA at a considerably low dosage of 250 μM L⁻¹. Adsorption of both inhibitors obeyed Langmuir adsorption isotherm and nature of adsorption is mixed type adsorption. Potentiodynamic polarization studies showed that both the compounds adsorb at the cathodic and anodic sites of the substrate surface to mitigate corrosion process and both inhibitors act as mixed type corrosion inhibitor. The surface study uninhibited and inhibited sample was done through SEM, EDX, AFM, FT-IR and XPS analysis and suggested the formation of protective layer of inhibitor molecules on the N80 steel surface to mitigate its corrosion. The theoretical analysis (DFT and Monte Carlo simulations) of both inhibitors correlates the experimental findings.