Anticorrosion effect of thiosemicarbazide derivative on mild steel in 1 M hydrochloric acid and 0.5 M sulfuric Acid: Gravimetrical and theoretical studies

The worldwide economic challenge of metal corrosion is crucial. The use of inhibitors, particularly organic inhibitors, is one of the greatest strategies to protect metal surfaces against corrosion. This research evaluates anti-corrosive characteristics of inhibitor compound (EOPT) namely 4-ethyl-1-(4-oxo-4-phenylbutanoyl)thiosemicarbazide on mild steel (MS) in 1 M HCl and 0.5 M H2SO4 solutions. The inhibition efficiency of EOPT was investigated utilizing weight loss measurements (WL), adsorption isotherm, and theoretical investigation utilizing density functional theory (DFT) within the concentration range of 100 to 600 ppm at the solution Temperature 303, 313, 323 and 333 K for the exposure period 1, 5, 10, and 24 h. The experimental findings showed that increasing the concentration of EOPT increases the inhibition efficiency (from 67.4 to 96.1% in HCl solution and from 55.3 to 88.7% inH2SO4 solution for 500 ppm and immersion time 5 h), whereas the inhibitive efficacy order for EOPT is HCl solution > H2SO4 solution with the significant inhibiting efficacy, each of 97.0, and 89.9% for 600 ppm and immersion time 10 h. Additionally, WL analyses showed that the adsorption of EOPT molecules obeys the Langmuir isotherm model in both acidic solutions. The studied inhibitor is well absorbed by the sites of adhesion on the MS surface by all the chemical descriptors determined from the DFT. The molecular geometry and electronic structure were determined by applying quantum chemical computations. DFT calculated to depict chemical reactivates and kinetic stabilities of the molecular structure, the energies between frontier molecular orbitals have been calculated (HOMO and LUMO)