Inhibitive effects of a novel efficient Schiff base on mild steel in hydrochloric acid environment

The corrosion inhibition performance of a novel Schiff base, namely 5-((4-fluoro-benzylidene)amino)-1,3,4-thiadiazole-2-thiol (FATT), on mild steel in 1.0 M hydrochloric acid environment has been studied by the weight loss method and scanning electron microscope (SEM). The inhibition efficiencies and the adsorption characteristics were determined from the gravimetrical results. The inhibition effectiveness increases with an increase in the concentration of the studied inhibitor but decreases with rising solution temperature. The inhibitor molecules are adsorbed on the coupon (mild steel) surface and obey the Langmuir adsorption isotherm. Scanning electron spectroscopy (SEM) was utilized to test the coupon surface morphology without and with the inhibitor at a concentration of 0.5 mM at 303 K. SEM implies the formation of a protective layer of FATT molecules on the coupon surface in the hydrochloric acid solution at 303 K. Quantum chemical calculations using density functional theory (DFT) were employed to identify the relationship between the electronic structure parameters of the FATT molecule and the inhibition efficiency. The quantum chemical parameters such as HOMO (highest occupied molecular orbital), LUMO (lowest unoccupied molecular orbital), Delta E (energy gap), mu (dipole moment), chi (electronegativity), eta (global chemical hardness), sigma (softness), and Delta N (fraction of electrons transferred) were calculated. The quantum chemical parameters by calculated the DFT method for the tested inhibitor agree with the experimental inhibition efficiency.

Automated summary

The study found that the novel Schiff base FATT demonstrates significant corrosion inhibition performance on mild steel in hydrochloric acid solution, with the effectiveness increasing with concentration but decreasing with temperature. SEM analysis showed the formation of a protective layer of FATT molecules on the steel surface at high temperatures. Quantum chemical calculations using DFT method confirmed the relationship between electronic structure parameters of FATT and inhibition efficiency.