Experimental, DFT calculations and MC simulations concept of novel quinazolinone derivatives as corrosion inhibitor for mild steel in 1.0 M HCl medium

Experimental and computational approaches of methoxy naphthylbithiophene derivatives and their use as corrosion protection for carbon steel in acidic medium

The inhibition efficiency and adsorption affinity were investigated for two novel compounds, namely: 6-methoxy-2-naphthyl-[2, 2'-bithiophene]-5-carboxamidine hydrochloride salt (MA-1440) and 5'-(4-chlorophenyl)-2, 2'-bifuran-5-carboxamidine hydrochloride salt (MA-1456). The inhibition study was conducted on carbon steel surface in 1.0 M HCl with different inhibitor doses and different temperature levels, to investigate the optimum dose and preferable temperature. The performed investigation included chemical, electrochemical, instrumental, and quantum computation techniques. A chemical technique was accomplished by using weight-loss measurements. Different factors were studied using weight-loss measurements in order to reach the maximum inhibition efficiency. The adsorption study revealed that the examined inhibitors obey the Langmuir adsorption isotherm and are chemically adsorbed on the steel surface. The electrochemical measurements were accomplished through the electrochemical impedance (EIS) and potentiodynamic polarization (PDP) techniques. Based on the electrochemical measurements, the examined compounds were categorized as mixed inhibitors. The instrumental examination using different techniques namely: scanning electron microscope (SEM), energy dispersive X-ray (EDX), Fourier-transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS) confirmed that the considered inhibitors are excellently adsorbed over the carbon steel surface. The extent of the adsorption affinity of these compounds on the carbon steel surface was studied theoretically using quantum computations and Monte Carlo simulation. The theoretical investigation results of quantum chemistry were validated with those obtained by chemical and electrochemical methodologies. All investigations prove that, the tested compounds were adsorbed chemically on the steel surface and achieved maximum inhibition efficiency of, 94.69% and 90.85% for M-1440 and MA-1456, respectively, at the optimum concentration 30 [Formula: see text] 10^-6 mol L^-1 and temperature 328 K.

Fenugreek seed and cape gooseberry leaf extracts as green corrosion inhibitors for steel in the phosphoric acid industry

Phosphoric acid is the core material for the fertilizer industry; however, it is incredibly corrosive to manufacturing plants' structures, mainly steel. Corrosion is one of the most severe problems encountered during phosphate fertilizer manufacturing. Recently, plant extracts have been commonly used as corrosion inhibitors because they are cheap and environmentally friendly. Steel corrosion in a 20% aqueous phosphoric acid solution in the absence and presence of fenugreek seed (Fen) or cape gooseberry leaf (CgL) extracts was investigated using the electrochemical impedance spectroscopy technique, potentiodynamic polarization measurement, scanning electron microscope, and quantum chemical calculations. Fourier Transform Infrared, FTIR, was used to identify the functional groups in Fen and CgL extracts. The inhibition efficiency for steel in 20% aqueous phosphoric acid was roughly equal to 80% for 0.4 g/L CgL and 1.2 g/L Fen extracts. A scanning electron microscope showed that the chemical constituents of extracts block the surface roughness of steel, decreasing the corrosion rate. The activation parameters indicated the effectiveness of the extracts at a higher temperature. Measurements of the potential of zero charges showed that the steel surface is positively charged in the phosphoric acid solution. Quantum chemical computations were also employed to examine the corrosion inhibition mechanisms of the natural extracts.

Vicia faba peel extracts bearing fatty acids moieties as a cost-effective and green corrosion inhibitor for mild steel in marine water: computational and electrochemical studies

The goal of this research is to determine what chemicals are present in two different extracts (hexane and acetone) of Vicia faba (family Fabaceae, VF) peels and evaluate their effectiveness as a corrosion inhibitor on mild steel in a saline media containing 3.5% sodium chloride. Gas chromatography-mass spectrometry (GC/MS) was used to determine the composition of various extracts. It was determined that fourteen different chemicals were present in the hexane extract, the most prominent of which were octacosane, tetrasodium tetracontane, palmitic acid, and ethyl palmitate. Heptacosane, lauric acid, myristic acid, ethyl palmitate, and methyl stearate were some of the 13 chemicals found in the acetone extract. Using open circuit potential, potentiodynamic polarisation, and electrochemical impedance spectroscopic techniques, we can approximate the inhibitory effects of (VF) extracts on mild steel. The most effective inhibitory concentrations were found to be 200 ppm for both the hexane and acetone extracts (97.84% for the hexane extract and 88.67% for the acetone extract). Evaluation experiments were conducted at 298 K, with a 3.5% (wt/v) NaCl content and a flow velocity of about 250 rpm. Langmuir adsorption isotherm shows that the two extracts function as a mixed-type inhibitor in nature. Docking models were used to investigate the putative mechanism of corrosion inhibition, and GC/MS was used to identify the major and secondary components of the two extracts. Surface roughness values were calculated after analyzing the morphology of the metal's surface with and without (VF) using a scanning electron microscope (SEM). The results showed that throughout the surface of the mild steel, a thick adsorbate layer was formed. Quantum chemical calculations conducted on the two extracts as part of the theoretical research of quantum chemical calculation demonstrated a connection between the experimental analysis results and the theoretical study of the major chemical components.

Functional Pyromellitic Diimide as a Corrosion Inhibitor for Galvanized Steel: An Atomic-Scale Engineering

Corrosion of metal/steel is a major concern in terms of safety, durability, cost, and environment. We have studied a cost-effective, nontoxic, and environmentally friendly pyromellitic diimide (PMDI) compound as a corrosion inhibitor for galvanized steel through density functional theory. An atomic-scale engineering through the functionalization of PMDI is performed to showcase the enhancement in corrosion inhibition and strengthen the interaction between functionalized PMDI (F-PMDI) and zinc oxide (naturally existing on galvanized steel). PMDI is functionalized with methyl/diamine groups (inh1 (R = -CH₃, R' = -CH₃), inh2 (R = -CH₃, R' = -CH₂CH₂NH₂), and inh3 (R = -C₆H₃(NH₂)₂, R' = -CH₂CH₂NH₂). The corrosion inhibition parameters (e.g., orbital energies, electronegativity, dipole moment, global hardness, and electron transfer) indicate the superior corrosion inhibition performance of inh3 (inh3 > inh2 > inh1). Inh3 (∼182.38 kJ/mol) strongly interacts with ZnO(101̅0) compared to inh2 (∼122.56 kJ/mol) and inh1 (∼119.66 kJ/mol). The superior performance of inh3 has been probed through charge density and density of states. Larger available states of N and H (of inh3) interact strongly with Zn and O_surf (of the surface), respectively, creating N-Zn and H-O_surf bonds. Interestingly, these bonds only appear in inh3. The charge accumulation on O_surf, and depletion on H(s), further strengthens the bonding between inh3 and ZnO(101̅0). The microscopic understanding obtained in this study will be useful to develop low-cost and efficient corrosion inhibitors for galvanized steel.