Experimental and theoretical study of the corrosion inhibition effect of 1-aryl-2,5-dithiohydrazodicarbonamide derivatives on metal in chloride solution

In this thesis, new compounds namely, 2- Fluoro phenyl-2,5- dithiohydrazodicarbonamide (2-Fluoro-PDCA), 4-Fluoro phenyl-2,5- dithiohydrazodicarbonamide (4-Floro-PDCA), and 2-ethyl phenyl-2,5-dithiohydrazodicarbonamide (2-Ethyl-PDCA) were synthesized and tested as corrosion inhibitor for mild steel (MS) in 1 M HCl and as well as they tested as corrosion inihbitors for copper (Cu) in 3,5% NaCl. The molecular structures were characterized by FT-IR and 1H, 13C NMR. A SEM, EDX, and AFM were conducted to identify the surface morphology of MS system (or copper system) in the presence and existence of a corrosion inhibitors. Both experimental and computational approaches have been conducted to evaluate inhibitor efficiency on both metal systems. The resistance polarization for inhibitors was found to obey an order in MS system 2-Ethyl-PDCA ˃ 4-Fluoro-PDCA ˃ 2-Fluoro-PDCA (IE = 97,6% compared with 95,4%, and 93,7%, respectively at 1 × 10-2 M and an immersion time of 5 h), while in copper system, it was found to obey 4-Fluoro-PDCA ˃ 2-Fluoro-PDCA ˃ 2-Ethyl-PDCA (IE = 99,3% compared with 99,2%, and 98,7%, respectively at 1 × 10-2 M and an immersion time of 5 h). The Langmuir isotherm system revealed the best match, and the type of adsorption was m in both systems. Quantum chemical results showed that the adsorption molecules of inhibitors take place predominantly through protonated structures, and strongly agreed with experimental results. In addition, DFT results indicate that the superior corrosion inhibition efficacy of inhibitors on copper compared to mild steel surfaces is attributable to the former's greater electron donating property on copper.