Performance of triazole derivatives as potential corrosion in-hibitors for mild steel in a strong phosphoric acid medium

Four Trizaoles (TRi) were investigated as corrosion inhibitors on mild steel (MS) in strong H3PO4 medium by weight loss measurements. TR3 exhibited the highest inhibition activity of 89.47 % at 10−3 M and 308(± 0.5) K. Global and local reactivity descriptors were computed at the DFT/B3LYP/6−31+G** level of theory to evaluate the correlation between the corrosion inhibition activity and the electronic characteristics of TRi. To mimic the real inhibition system (2 M H3PO4), the protonation process of TRi was regarded. Attempts to correlate the theoretical calculations with the observed behaviours showed that the protonation process affected unfavourably the prohibition of TRi. Results demonstrated that the hydration energy (ΔGhyd) may be regarded as a valuable descriptor to inspect the inhibition performance of organic compounds. The Fukui functions and local softness indicated that the azine (=N-N=) link in the triazole ring is the privileged site for the adsorption of the inhibitor. Molecular dynamics (MDs) simulation were exerted to inspect the adsorption geometry of {TRi/50H2O/3H3O+/PO43−/Fe(110)} complexes in the neutral and protonated inhibitory configurations. The outcomes of this work show that TR3 is the pre-eminent inhibitory molecule of the studied systems for both neutral and protonated configurations. The adsorption of TRi was performed spontaneously according to Langmuir's model. The =N-N= moiety in the triazolic ring are the privileged sites of adsorption. The electron-donating substituent (both para-methoxy) effects on the tautomeric mesomeric equilibrium observed on the triazolic ring of TR3 was behind its higher inhibition. QSAR results gave an accurate interdependence between the presaged and experimental research (R² ≈ 1). Coupling GRDs with MDs descriptors enabled to gain further insights into the physical-chemistry of TRi.