Inhibition impact of 1-phenyl-2-pyrazolin-5-one derivatives on corrosion of 304 stainless steel in molar HCl solution

• A.S. Fouda¹, S.M. Rashwan², M.M. Kamel², A.H.M. Gad² and K. Shalabi¹

¹ Department of Chemistry, Faculty of Science, Mansoura University, Mansoura 35516, Egypt
² Department of Chemistry, Faculty of Science, Suez Canal University, Egypt

Abstract: Chemical and electrochemical methods such as weight loss (WL) method, potentiodynamic polarization (PP), electrochemical impedance spectroscopy (EIS), and electrochemical frequency modulation (EFM) techniques were utilized to study 1-phenyl-2-pyrazolin-5-one (PPO) derivatives as safe corrosion inhibitors for 304 stainless steel (SS 304) in 1.0 M HCl. The inhibition efficiencies and adsorption characteristics were determined from the WL results. The results indicated that the protection efficiency (%IE) rises with an increase in the concentration of 1-phenyl-2-pyrazolin-5-one derivatives. The adsorption of these derivatives on the surface of SS 304 follows the Langmuir isotherm. The 1-phenyl-2-pyrazolin-5-one derivatives are good inhibitors for the dissolution of SS 304 in 1 M HCl and they are mixed-type inhibitors. Analysis of data on the free adsorption energy of 1-phenyl-2-pyrazolin-5-one derivatives on the surface of SS 304 in acid media frequently allows assuming the chemisorption character of their interaction, which to a large extent explains the efficiency of these compounds in corrosion inhibition. At 298 K, atomic force microscopy (AFM) was used to examine the coupon surface morphology without and with inhibitors at a concentration of 24·10^–6 M. The development of a protective layer of derivative molecules on the coupon surface in the hydrochloric acid solution at 298 K is suggested by AFM. Density functional theory (DFT) quantum chemical computations were used to determine the relationship between the electronic structural characteristics of the 1-phenyl-2-pyrazolin-5-one derivative molecules and the inhibitory efficiency. HOMO (highest occupied molecular orbital), LUMO (lowest unoccupied molecular orbital), E (energy gap), µ (dipole moment), and A₀ (molecular surface area) were computed. The quantum chemical parameters of the studied inhibitors estimated using the DFT technique accord with the experimental inhibitory efficiency.

Keywords: corrosion inhibition, 304 stainless steel, EIS, EFM, SEM, AFM, DFT

Int. J. Corros. Scale Inhib., 2021, 10, no. 4, 1407-1427
doi: 10.17675/2305-6894-2021-10-4-3

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