Two phenylpyrimidine derivatives as new corrosion inhibitors for cold rolled steel in hydrochloric acid solution

• 4-PPM and 5-PPM are new good inhibitors for steel in HCl solution.
• Inhibition efficiency follows the order: 4-PPM > 5-PPM.
• The adsorption of phenylpyrimidine inhibitor obeys Langmuir adsorption isotherm.
• There is a correlation between quantum chemical parameters and inhibition action.
• 4-PPM and 5-PPM molecules adsorb on Fe (0 0 1) surface in the nearly flat manner.

The inhibition effect of two phenylpyrimidine derivatives of 4-phenylpyrimidine (4-PPM) and 5-phenylpyrimidine (5-PPM) on the corrosion of cold rolled steel (CRS) in HCl solution was studied by weight loss, polarization curves, electrochemical impedance spectroscopy (EIS) and scanning electron microscope (SEM) methods. Quantum chemical calculation and molecular dynamics (MD) were applied to theoretically determine the relationship between molecular structure and inhibition efficiency. The results show that two phenylpyrimidine derivatives are good inhibitors, and inhibition efficiency follows the order: 4-PPM > 5-PPM. The adsorption of each inhibitor on steel surface obeys Langmuir adsorption isotherm. Two phenylpyrimidine derivatives act as mixed-type inhibitors.