Comparison between Schiff-base and its iron complex as steel corrosion inhibitors used by the petroleum industry in marine environments

Abstract

ABSTRACT The Schiff-base N,N-bis(2-furaldehyde)−1,3-diaminopropane (FDP) and its complex with iron (FDPIC) were prepared and used as corrosion inhibitors for mild-steel (MS) in a 3.5% NaCl medium as an artificial marine environment to evaluate the functional groups’ efficiency within the structure of the compounds for corrosion inhibition. To predict the effect of the researched inhibitors’ ability to suppress corrosion, weight loss measurements and a variety of complex analytical techniques, including potentiodynamic-polarisation and electrochemical-impedance tests, were applied. Experimental results revealed that (FDPIC) has a higher corrosion inhibition efficacy than (FDP). According to electrochemical measurements, inhibitors showed significant resistance to charge transfer through the electrolyte–metal interface and mixed-type inhibitor behaviour. Furthermore, the film formed on the surface of the mild steel was examined using a scanning electron microscope (SEM). Quantum chemical calculations using semi-empirical molecular orbital PM3 and Molecular Dynamics (MD) were used to investigate inhibitor adsorption and inhibition on the mild-steel surface. The geometry of the Schiff-base and its complex structures, as well as electron density distribution in LUMO, HOMO, and QSAR properties of each atom for their conceivable interaction mode with the mild-steel surface, were used in chemical quantum calculations. According to molecular dynamic simulations, all of the inhibitor molecules adhered to the surface in a parallel direction.