Investigation of corrosion inhibition of carbon steel in 0.5Â M H2SO4 by new bipyrazole derivative using experimental and theoretical approaches

2-[Bis-(3,5-dimethyl-pyrazol-1-ylmethyl)-amino]-4-[bis-(3,5-dimethyl-pyrazol-1-ylmethyl) carbamoyl]-butyric acid (Pyr1-1) has been evaluated as a corrosion inhibitor for carbon steel using weight loss and electrochemical polarization (EIS). The study was also complemented by scanning electron microscopy (SEM) and quantum chemical calculations. The inhibition efficiency (η%) increased with increasing Pyr1-1 concentration, showing a maximum IE of 93.5% at 298 K at 10−3 M and decreased with increasing temperature. The electrochemical studies showed that Pyr1-1 inhibitor retards both cathodic and anodic processes through the inhibitor adsorption on the metal surface and blocking the active corrosion sites. The corrosion current density is the order 165.8 μA/cm2 of Pyr1-1 at the optimum concentration. EIS results show that the change in the impedance parameters (Rct and Cdl) with concentration of Pyr1-1 is indicative of the adsorption of molecules leading to the formation of a protective layer on the surface of carbon steel. A good fit to Langmuir adsorption isotherm was obtained between surface coverage degree and inhibitor concentration. The results obtained by weight loss measurements are consistent with the results of the electrochemical study. Quantum chemical approach used to calculate electronic properties of the molecule to ascertain the relation between inhibitive effect and molecular structure. The equilibrium adsorption behavior of this molecule on Fe (1 1 0) surface was investigated using molecular dynamics simulation.