Adsorption and inhibition effect of 6-benzylaminopurine on cold rolled steel in 1.0 M HCl

The adsorption and inhibition effect of 6-benzylaminopurine (BAP) on cold rolled steel (CRS) in 1.0 M HCl at 25–50 °C was studied by weight loss and potentiodynamic polarization methods. The results showed that BAP was a good inhibitor in 1.0 M HCl, and the inhibition efficiency (IE) increased with the inhibitor concentration. The adsorption of BAP on the CRS surface obeyed the Langmuir adsorption isotherm equation. Both thermodynamic parameters (adsorption heat ΔH0, adsorption free energy ΔG0 and adsorption entropy ΔS0) and kinetic parameters (apparent activation energy Ea and pre-exponential factor A) were calculated and discussed. Polarization curves showed that BAP acted as a mixed-type inhibitor in hydrochloric acid. Good agreement between weight loss and polarization methods was obtained. The adsorbed film on CRS surface containing optimum dose of BAP was investigated by Fourier transform infrared spectroscopy (FTIR) and atomic force microscope (AFM). Quantum chemical calculation was applied to elucidate the adsorption mode of the inhibitor molecule onto steel surface. Depending on the results, the inhibitive mechanism was proposed from the viewpoint of adsorption theory.