Two novel phosphoramide derivatives moiety as corrosion inhibitor for mild steel: Experimental and theoretical study

Abstract

Two novel phosphoramide containing thiazole derivatives with the name of bis(5‐amino‐1,3,4‐thiadiazol‐2‐yl) phenylphosphonotrithioate (C1) and O, O‐diethyl (5‐((diethoxyphosphorothioyl) thio)‐1,3,4‐thiadiazol‐2yl) phosphoramidothioate (C2) as corrosion inhibition were synthesized and identified by 1H NMR, 13C NMR, 31P NMR, IR, and mass spectroscopies. The electrochemical behavior of mild steel (MS) in hydrochloric acid 1‐M (HCl) solution was perused in the absence and presence of C1 and C2. To determine corrosion inhibition of phosphoramide compounds, scanning electron microscopy (SEM), potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS) were used. The EIS results show that the charge transfer resistance increases with the addition of inhibitors to the hydrochloric acid solution. The most inhibitor efficiency was 89%, which demonstrated the appropriate anti‐corrosion property of C1. EIS results show better charge transfer resistance on the surface of MS at increased inhibitor concentrations. The PDP analysis showed that C1 and C2 are mixed‐type inhibitors. The PDP examination appeared that C1 and C2 are mixed‐type inhibitors. To way better get the comes about of corrosion inhibition and structure of target compounds, the highest occupied molecular orbital (HOMO) and least unoccupied molecular orbital (LUMO) energies, hardness, dipole moment, and electrophilicity index of synthesized compounds were explored computationally using the density functional theory (DFT) strategy. The hypothetical comes about in great understanding with the exploratory information.