An Exploratory Experimental Analysis Backed by Quantum Mechanical Modeling, Spectroscopic, and Surface Study for C-Steel Surface in the Presence of Hydrazone-Based Schiff Bases to Fix Corrosion Defects in Acidic Media.

This work focuses on developing corrosion control and protecting the environment by creating affordable, sustainable, environmentally friendly, and efficient corrosion resistance chemicals. That is, through synthesized three hydrazone Schiff bases E-2-(1-hydrazonoethyl)thiazole (HTZ), 2-((E)-(((Z)-1-(thiazol-2-yl)ethylidene)hydrazono)methyl)phenol (HTZS), and 2-((E)-(((Z)-1-(pyridin-2-yl)ethylidene)hydrazono)methyl)phenol (HPYS) and corrosion inhibitors for C-steel in 8 M H3PO4 solution that were studied. The chemicals were analyzed by using 1H NMR and 13C NMR spectroscopy to learn more about them. Predominantly, the hydrazone-based Schiff bases have been considered powerful inhibitors due to their ability to be adsorbed with very low concentrations through their reactive sites (N, O, and S). Maximum surface (θmax) coverage and inhibition efficiency of 83.33% were sufficiently found at 99.00 × 10-3 mol/L concentration of HTZS at 293 K. Galvanostatic experiments demonstrated that raising the concentration of hydrazones improved mass transfer resistance. To study microstructure, scanning, reflectance, and energy-dispersive X-rays were used. Roughness and qualitative adhesion of the adsorbed layer were estimated by an atomic force microscope. After adding 99.00 × 10-3 mol/L of HTZS, the degree of surface brightness and reflectance increases to 137.20, relative to the corroded electrolyte-free solution 27.70. The roughness (Ra) decreased from 0.468 to 0.088 µm by adding HTZS. A surface morphology study confirmed that adding hydrazones to the C-steel dissolution bath greatly improves the surface's look and texture quality. The atomic absorption spectroscopy technique was used to compare the concentration of the iron ions that remained in the solution after galvanostatic analysis in the absence and presence of the hydrazones under different conditions; it was found that the inhibited solution contained lower concentrations of iron ions as compared to the uninhibited solution. The DFT theoretical analysis verified the observation of hydrazone physical adsorption through bonding electrons that obey kinetic adsorption isotherms. It is based on examining the highest occupied molecular orbital-lowest occupied molecular orbital (HOMO-LUMO), the Fukui functions, and the Mulliken atomic charge. Overall, the results suggest that HTZS is a good corrosion inhibitor with a large surface area due to the presence of S, N, and O atoms, allowing for creating a larger surface due to the large molecular volume of atoms protecting against the corrosion process.

Anticorrosive performance of newly synthesized dipyridine based ionic liquids by experimental and theoretical approaches.

Two newly synthetic nontoxic dipyridine-based ionic liquids (PILs) with the same chain lengths and different polar groups were investigated: bispyridine-1-ium tetrafluoroborate (BPHP, TFPHP) with terminal polar groups Br and CF3, respectively, on Carbon steel (CS) in 8M H3PO4 as corrosion inhibitors. Their chemical structure was verified by performing 1HNMR and 13CNMR. Their corrosion inhibition was investigated by electrochemical tests, especially as mass transfer with several characterizations: Scanning electron microscope/Energy dispersive X-ray spectroscopy (SEM-EDX), UV-visible, Atomic force microscope, Atomic absorbance spectroscopy, X-ray Photoelectron Spectroscopy and Gloss value. Theoretical calculation using density functional theory by calculating several parameters, molecular electrostatic potential, Fukui Indices, and Local Dual Descriptors were performed to demonstrate the reactivity behavior and the reactive sites of two molecules with a concentration range (1.25-37.5 × 10-5 M) and temperature (293-318 K). The maximum inhibition efficiency (76.19%) and uniform coverage were sufficient for BPHP at an optimum concentration of 37.5 × 10-5 M with the lowest temperature of 293 K. TFPHP recorded 71.43% at the same conditions. Two PILs were adsorbed following the El-Awady adsorption isotherm, including physicochemical adsorption. The computational findings agree with Electrochemical measurements and thus confirm CS's corrosion protection in an aggressive environment.

Functionalization Strategies for Electropolishing Process of Carbon Steel Using Novel Quinazoline-4-one Derivatives: Synthesis, Spectroscopic Characterization, and DFT Studies.

A novel class of organic electropolishing (EP) inhibitors, entitled quinazoline-4-one derivatives (benzylidene oxoquinazolineyl acetohydrazide (BOA)), has laid a solid foundation for the creation of a new efficient inhibitor platform for the dissolution of carbon steel (C-steel) in 8 M H3PO4. Fourier-transform infrared (FTIR), 1H NMR, and elemental analyses have all been employed to identify BOA's functional groups, components, and active centers. The inhibition strength of BOA derivatives (m-NBOA, p-HBOA, and p-BBOA) on C-steel was assured by galvanostatic polarization measurements. Within the range of concentrations (0.33-3.43 × 10-3 mol/L) and temperatures (298-313 K) evaluated, the tested derivatives exhibit extraordinarily high gloss and low roughness, and improved the corrosion resistance of the electropolished surface with the lowest negative environmental impact. The dissolution rate (IL) decreases with increasing BOA concentration, supporting a mass transport-controlled technique and demonstrating that BOA is appropriate for anodic inhibitors. Activation energy indicates physical adsorption. Thermodynamic parameters were calculated for further investigation of the heat involved and the mechanism of the EP process. Adsorption isotherm and adsorption thermodynamics parameters were discussed using three models: Langmuir, Flory-Huggins, and kinetic adsorption isotherms, to study the inhibition of EP of the steel surface. The free energy of adsorption was calculated to assert the physisorption process. A scanning electron microscope (SEM) was utilized to inspect the morphology of the metal surface before and after the inclusion of BOA under different conditions. In contrast, the surface roughness was identified using an atomic force microscope (AFM) and reflectance. Eventually, practical results have been proved through computational calculations using the LYP correlation functional by the density functional theory (DFT) method.