Inhibition effect of two mercaptopyrimidine derivatives on cold rolled steel in HCl solution

•AHMP and DHMP are good mixed-type inhibitors for steel in HCl solution.•AHMP exhibits better inhibitive ability than DHMP.•Inhibition efficiency remains constant from 6 to 156 h.•N8 and O9 atoms of AHMP exhibits more active than those of DHMP.•AHMP and DHMP molecules adsorb on Fe (0 0 1) surface with a nearby flat orientation.

The inhibition effect of two mercaptopyrimidine derivatives of 4-amino-6-hydroxy-2-mercaptopyrimidine (AHMP) and 4,6-dihydroxy-2-mercaptopyrimidine (DHMP) on cold rolled steel (CRS) in HCl solution was studied by weight loss, potentiodynamic polarization curves, electrochemical impedance spectroscopy (EIS), scanning electron microscope (SEM), quantum chemical calculation and molecular dynamics (MD) simulations methods. The results show that both mercaptopyrimidine derivatives act as good inhibitors, and inhibition efficiency follows the order: AHMP > DHMP. The adsorption of either inhibitor on steel surface obeys Langmuir adsorption isotherm. Two mercaptopyrimidine derivatives are mixed-type inhibitors. The inhibitor molecules adsorb on the Fe (0 0 1) surface in the nearly flat manner.