New pyrimidine derivatives as efficient organic inhibitors on mild steel corrosion in acidic medium: Electrochemical, SEM, EDX, AFM and DFT studies

New pyrimidine derivatives, namely, 7-methoxypyrido [2,3-d]pyrimidin-4-amine (MPPA) and 4-amino-7-methoxypyrido[2,3-d]pyrimidin-2(1H)-one (AMPO) were synthesized and their inhibitive action against the corrosion of mild steel in 15% HCl solution was studied by weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. Polarization studies showed that both studied inhibitors were of mixed type in nature. The adsorption of inhibitors on the mild steel surface obeys Langmuir adsorption isotherm. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and atomic force microscopy (AFM) were performed for surface study of uninhibited and inhibited mild steel samples. Density functional theory (DFT) was employed for theoretical calculations.