Sunflower Head Pectin with Different Molecular Weights as Promising Green Corrosion Inhibitors of Carbon Steel in Hydrochloric Acid Solution

Abstract

Three sunflower head pectin (SFHP) with different molecular weights (Mw = 4.50, 97.23, and 254.64 kDa) were obtained by enzyme-assisted extraction and characterized by FTIR and 1H NMR spectroscopy. The corrosion inhibition of mild steel in 1 M HCl solution was evaluated by the weight loss measurement. The inhibition efficiency (IE%) increased as its concentration increases and decreased as the temperature increases. The SFHP with the lowest Mw of 4.50 kDa exhibited an IEmax of 92.05% at the medium concentration (2.0 g L–1). The inhibition properties of SFHP (Mw = 4.50 kDa) were investigated electrochemically and theoretically. The electrochemical impedance spectroscopy (EIS) revealed that the charge-transfer resistance increased as its concentration increases, the double-layer capacitance decreased as concentration increases, and the IE% also increased as concentration increases. The potentiodynamic polarization (PP) revealed that the SFHP acted as mixed-type inhibitor. The IE% reached 90.3% at the medium concentration (2.0 g L–1) of SHFP. The three-dimensional super depth digital microscopy and scanning electron microscopy tests confirmed the formation of inhibitor films on the surface of mild steel. The adsorption of SFHP on the mild steel surface was proved to obey the Langmuir adsorption isotherm. The theoretical studies via density functional theory and molecular dynamics simulation further revealed the mechanism of corrosion inhibition.

Inhibition Evaluation of Chromotrope Dyes for the Corrosion of Mild Steel in an Acidic Environment: Thermodynamic and Kinetic Aspects

“…The nature of the adsorption process may be physical, chemical, or a mixture of the two-mentioned adsorption types. 36 The evaluated thermodynamic and kinetic parameters in the present study supported that the nature of adsorption of the two examined inhibitors on the steel surface in H 2 SO 4 solution was mainly physical. Adsorption of the inhibitor molecules on the steel surface was set to depend on their chemical structures, intensity of surface charge, potential of zero charge (PZC) of metal, and the composition of the corrosive environment.…”

“…The evaluated values of E a * (Table 5) in the presence of the inhibitors were found to be higher than those obtained in the corrosive solution verifying adsorption of the tested molecules on the mild steel surface and constructing a barrier between the steel surface and the corrosive medium. 36 Furthermore, the range of E a * values (5.86−20.78 kJ mol −1 ) is lower than 80 kJ mol −1 confirming the physical adsorption of the examined inhibitors. 41 These results are in good agreement with those based on the values of both ΔG o ads and ΔH o ads indicating the validity of the acquired investigational outcomes.…”

Corrosion Control of Carbon Steel in Water-Based Mud by Nanosized Metallo-Cationic Surfactant Complexes During Drilling Operations

“…The open-circuit potential (OCP) of the carbon steel electrode is a parameter that depends on the immersion time in the test solution. 38 Measurements were performed until the steady-state potentials were achieved, at which the equilibrium state occurs between the oxidation current ( i oxd ) and reduction current ( i red ). Figure 7 exhibits the variation of OCP ( E OCP ) as a function of the immersion time in the absence and presence of CT-Cu inhibitor at different doses in the WBM at 25 °C.…”

Synthesis of 1,8-Naphthyridines by the Ionic Liquid-Catalyzed Friedlander Reaction and Application in Corrosion Inhibition

“…It is observed that R ct values increase significantly in the presence of [1,8-Nap]­[CETSA], while the C dl value decrease is probably attributed to the replacement of water and HCl molecules with large dielectric constants of [1,8-Nap]­[CETSA] molecules; these results illustrate that a protective layer formed on the metal surface to inhibit the corrosion process. Meanwhile, the EIS measurement showed that η was over 90%, and inhibitor molecules can be stably adsorbed on the surface of Q235 steel.…”