Iron-ligand complex, an efficient inhibitor of steel corrosion in hydrochloric acid media

•The FeSO4(Hdpz) complex exhibited excellent inhibition efficiency against mild steel corrosion in 1 M HCl.•Polarization curves shows that the complex FeSO4(Hdpz) basically functions as a mixed inhibitor.•The quantum approach and monte carlo simulation was confirmed the reactivity of the studied compound towards the corrosion process.•The gibbs free energy values for the adsorption process indicated that physical and chemical adsorption mechanisms were involved. The inhibitor effect of FeSO4(Hdpz) complex prepared from iron (II) sulfate7-hydrate and 1-Hydroxymethyl-3,5-dimethylpyrazole on corrosion of mild steel in 1 M hydrochloric acid (HCl) at 308 K was investigated using measurements of weight loss and electrochemical techniques (impedance spectroscopy and polarization curves). Inhibition efficiency depends on the concentration of complex [FeSO4 (Hdpz)] and its inhibition efficiency increases with an increase in inhibitor concentration to 98% for 10−3 M. Polarization curves show that the complex FeSO4(Hdpz) basically functions as a mixed inhibitor. Measurements of electrochemical impedance spectroscopy (EIS) indicate an increase in transfer resistance at the concentration of the inhibitor. In the temperature range of 308 to 348 K, the temperature effect on the corrosion behavior of steel in 1 M HCl without and with the inhibitor at 10−3 M was studied and the corresponding activation energy was calculated. Adsorption of FeSO4(Hdpz) complex on the mild steel surface in 1 M HCl follows the Langmuir isotherm model. The quantum approach and monte Carlo simulation was confirmed the reactivity of the studied compound towards the corrosion process. [Display omitted]