Experimental and computational study of a multi-active-site Schiff base as corrosion inhibitor of mild steel in 1 M HCl

In this study, the corrosion inhibition behavior of N,N '-(1,4-phenylene)bis(1,1-di(pyridin-2-yl)methanimine) (PBDPM) on mild steel in 1 M HCl at 30 degrees C was evaluated under steady conditions. The corrosion inhibitor was synthesized by a one-step method. Electrochemical, energy dispersion spectrum (EDS) and water contact angle results revealed the adsorption behavior of the inhibitor at the metal-solution interface. The adsorption of PBDPM obeys the Langmuir adsorption isotherm. It is obvious that PBDPM exhibits good inhibition performance presumably due to its high surface coverage, as it forms a dense protective film on the surface of mild steel. The adsorption configuration and structure-activity relationships of the inhibitor were also explored theoretically by density functional theory (DFT) and molecular dynamics (MD), and the thermodynamic parameters and molecular active sites (the values of electrophilic attack and nucleophilic attack) were calculated. DFT calculations and MD simulation were used to analyse the corrosion inhibition activity and mechanism of N,N '-(1,4-phenylene)bis(1,1-di(pyridin-2-yl)methanimine) (PBDPM), and the structure-activity relationship was tested. The results from SEM and water contact angle and potentiodynamic polarisation curve measurements verify the adsorption behaviour of PBDPM on the surface of mild steel, and test that PBDPM plays a role in corrosion inhibition by changing the hydrophilic and hydrophobic properties of the surface of mild steel. (Image credit: Xiaolong Li.)