Insight into the corrosion inhibition and adsorption behavior of synthetic pyrazole surfactants as an efficient inhibitor for carbon steel in 1.0 mol/L HCl solutions

Two nonionic surfactants (NI Surf.) compounds derived from pyrazole were synthesized and inspected as inhibitors for corrosion of C-steel (CSt) in 1 mol/L HCl solution utilizing weight reduction (WR), potentiodynamic polarization (PDP) and electrochemical impedance spectroscopic (EIS) methods. The chemical compositions of the synthetic NI Surf. were proven by IR, H-1 and C-13 NMR. The corrosion and surface properties confirm the inhibitory effect of the NI Surf. compounds. The percentage of inhibitory efficacy (%) increases with increasing NI Surf concentration, and with decreasing temperature. PDP method has proven that the NI Surf. I and II act as mixed inhibitors. The maximum %eta was found to be 90.41% for the compound I and 91.45% for compound II at a concentration of 500 ppm at 292 K temperature using PDP measurements. The higher %eta of compound II is related to its chemical structure and the presence of more adsorption centers. The inhibition was demonstrated by its spontaneous adsorption on the CSt surface owing to the Freundlich isotherms. There is a clear agreement between the % values that were assigned from the different techniques.