Detailed characterization of Phellodendron chinense Schneid and its application in the corrosion inhibition of carbon steel in acidic media.

We present a combined experimental and theoretical study of the effective corrosion protection of carbon steel in 1 M HCl solution by Phellodendron chinense Schneid (PCS) bark extract. Fourier-transform infrared spectroscopy (FTIR) and liquid chromatography tandem multi-stage mass spectrometry (LC-MS) were employed for the extract characterization. The properties of PCS as a corrosion inhibitor were evaluated by electrochemical and gravimetric experiments. Quantum chemical calculation was used to describe the electronic and adsorption properties of the identified and characterized compounds found in the extract while molecular dynamics simulation was employed to predict the equilibrium configurations and binding energies of the compounds on the steel surface. The electrochemical results revealed that PCS acted as a mixed-type corrosion inhibitor whose efficiency increased with the extract concentration but slightly decreased with increasing temperature. Quantum chemical parameters, such as the energy difference (ΔE) and the number of transferred electrons (ΔN), were used to predict the contribution of each characterized compound to the inhibition process while molecular dynamics simulation predicted parallel orientations for the configuration of the compounds and high binding energies on the metal substrate.