New pyrazole derivatives as effective corrosion inhibitors on steel-electrolyte interface in 1 M HCl: Electrochemical, surface morphological (SEM) and computational analysis

Abstract Corrosion inhibition is a vast area of research and its development is attracting increasing attention from researchers. Given the different biological activities that present these compounds, in the present work, we investigated two dimethyl-1H-pyrazole derivatives namely: (E)-N'-benzylidene-2-(3,5-dimethyl-1H-pyrazol-1-yl)acetohydrazide (DPP) and E)-N'-(4-chlorobenzylidene)-2-(3,5-dimethyl-1H-pyrazol-1-yl)acetohydrazide (4-CP) as corrosion inhibitors for mild steel (MS) in 1 M HCl using weight loss (WL), electrochemical techniques [potentiodynamic (PP) polarization, electrochemical impedance spectroscopy (EIS)], surface examinations by scanning electron microscopy (SEM). Theoretical studies such as quantum chemical and molecular simulations studies were used to support the experimental findings. Analyses on mass loss (ML) and electrochemical properties confirmed adsorption of inhibitor as a protective layer on the surface of MS. The inhibition efficiency of DPP and 4-CP was enhanced as the concentration of inhibitors increased but decrease with rising temperature. The maximum inhibition efficiency for DPP and 4-CP at 10-3 M concentration has been obtained 80% and 94% respectively. Analysis of adsorption isotherms revealed that adsorption of DPP and 4-CP on MS surface follows Langmuir isotherm. Potentiodynamic polarization study confirmed that DPP and 4-CP are of mixed-kind inhibitors. EIS investigations displayed that the polarization resistance raised to 93.7 Ω cm2 and 287.7 for DPP and 4-CP, respectively at 10-3 M. Furthermore, to get detailed electronic/atomic-level findings regarding the dimethyl-1H-pyrazole derivatives interactions over the MS substrate, theoretical investigations applying molecular dynamics (MD) and density functional theory (DFT) methods were conducted. The results extracted from these approaches affirmed the DPP and 4-CP adsorption on the MS adsorbent.