Hydroxymethyl urea and 1,3-bis(hydroxymethyl) urea as corrosion inhibitors for steel in HCl solution

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

The inhibition effect of two urea derivatives of hydroxymethyl urea (HMU) and 1,3-bis(hydroxymethyl) urea (BHMU) on the corrosion of cold rolled steel (CRS) in 1.0 M HCl solution was studied by weight loss, potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS), quantum chemical calculation and molecular dynamics (MD) simulation methods. Inhibition efficiency values of 20.0 mM HMU and BHMU are higher than 80% and 85% at 20–50 °C, respectively. The adsorption of each inhibitor on steel surface obeys Langmuir adsorption isotherm, and is mainly the chemical adsorption. Inhibition efficiency follows the order: BHMU > HMU.