Development of a 2D Network of Zinc Organophosphate with an 8-Membered Ring Core Having Corrosion Resistance Properties

A 2D framework, i.e., zinc organophosphate [Zn(tmbiph)(solv)]2 (tmbiphH4 = tetramethyl-[1,1'-biphenyl]-4,4'-diyl bis(dihydrogen phosphate); solv = 2H2O) with an eight-membered ring core has been developed. The hierarchical and rational design of the zinc organophosphate has been achieved by carefully designing an organic bisphosphate ligand with two phosphate monoester groups connected through extended aromatic rings with methyl groups at ortho positions. The development of the 2D network does not require any ancillary ligand due to participating two phosphate groups in the coordination. The molecular structure of the zinc phosphate material was determined using single-crystal X-ray diffraction technique. The corresponding Co and Cu organophosphate materials have also been obtained using the same synthetic method; however, these compounds could not be confirmed structurally due to nondiffractive crystal quality. The structure of zinc organophosphate obtained through single-crystal X-ray diffraction has also been supported by theoretical calculations using density function theory. Furthermore, the zinc organophosphate material has been employed as an corrosion inhibitor for mild steel. The effect of the zinc phosphate framework on mild steel in 1 M HCl was investigated using polarization and electrochemical impedance spectroscopy. This study suggests that such phosphate inhibitors can be employed in the form of a thin protective layer on the electrode surface.

Chemical, electrochemical, and quantum investigation into the use of an organophosphorus derivative to inhibit copper corrosion in acidic environments

In order to protect the copper against corrosion, a novel corrosion inhibitor known as diphenyl ((2-aminoethyl) amino) (4-methoxyphenyl) methyl) phosphonate (DAMP) was developed. Acid solutions of HCl and H2SO4 were the aggressive solutions employed in this study. Analysis using the FT-IR, 1H-NMR, 31P-NMR, 13C-NMR and BET confirmed that the DAMP was successfully synthesized. The anti-corrosion capabilities of DAMP are evaluated using a combination of chemical, electrochemical and quantum studies. The DAMP has been found to be crucial in preventing the corrosion of copper in both HCl and H2SO4 acid. This was obviously implied by the observation that the corrosion rate of copper in acid solutions decreased when DAMP was added. It is significant to note that 180 ppm produced the highest levels of inhibiting efficiency (96.6% for HCl and 95.2% for H2SO4). The tendency of DAMP to adsorb on the surface of copper through its hetero-atoms (O, N, and P) is the main factor for the anti-corrosion capabilities of DAMP. Results from SEM/EDX tests supported this. The actual adsorption takes place via various active centers, physical and chemical mechanisms that are coordinated with the estimated quantum parameters. Additionally, the adsorption of DAMP adheres to the Langmuir isotherm.

Novel Corrosion Inhibitor for Carbon Steel in Acidic Solutions Based on α-Aminophosphonate (Chemical, Electrochemical, and Quantum Studies)

α-aminophosphonate (α-AP) is used as a novel corrosion inhibitor for carbon steel. The aggressive media applied in this study are HCl and H₂SO₄ acid solutions. The findings indicate that the morphology of the α-AP compound is cubic, with particles ranging in size from 17 to 23 μm. FT-IR, ¹HNMR, ³¹PNMR, and ¹³CNMR analysis confirmed the synthesis of the α-AP molecule. It has been discovered that the compound α-AP plays an important role in inhibiting the corrosion of carbon steel in both HCl and H₂SO₄ acids. This was identifiably inferred from the fact that the addition of α-AP compound decreased the corrosion rate. It is important to report that the maximum inhibition efficiency (92.4% for HCl and 95.7% for H₂SO₄) was obtained at 180 ppm. The primary factor affecting the rate at which steel specimens corrode in acidic electrolytes is the tendency of α-AP compounds to adsorb on the surface of steel through their heteroatoms (O, N, and P). This was verified by SEM/EDX results. The adsorption actually occurs through physical and chemical mechanisms via different active centers which are matched with the calculated quantum parameters. In addition, the adsorption of α-AP follows the Langmuir isotherm.

Antipsychotic drug waste: A potential corrosion inhibitor for mild steel in the oil and gas industry

In this study, the corrosion inhibition efficiency of thioridazine hydrochloride (TH), an antipsychotic drug, on mild steel (commonly used pipeline material in the oil and gas industry) in 1 M hydrochloric acid (HCl) was evaluated using electrochemical techniques and weight loss method. Electrochemical impedance spectroscopy (EIS) results suggest that TH significantly enhances the polarization resistance (R_p) of mild steel. Similarly, potentiodynamic polarization results showed that the corrosion current density (i_corr) of mild steel decreased significantly with addition of TH. To understand the long-term effect of TH, mild steel was tested for 7 days in 100 ppm TH containing electrolyte. EIS results showed that the R_p did not change significantly after 24 h exposure as compared to 2 h exposure; whereas the R_p increased by 28% after 7-day exposure. Weight loss measurements revealed that the inhibition efficiency of TH is remarkably high (98.8%) after 7-day exposure. The adsorption free energy calculation suggests that at the initial stage (1-day) of mild steel exposure, TH was physically adsorbed onto the surface. However, at a later stage (7- day) the binding of TH was chemical, and hence the corrosion protection increased with increase in the exposure period. As compared to the wide range of corrosion inhibitors reported in the literature, TH has shown to be highly effective for mild steel. Thus, it can be suggested that TH drug waste is a potential corrosion inhibitor for mild steel pipelines in the oil and gas industry.

Electrochemical and quantum chemical study to assess the role of (2E)-2-(furan-2-ylmethylidene) hydrazine carbothioamide as inhibitor for acid corrosion of mild steel

Synthesis and inhibition effectiveness of (2E)-2-(furan-2-ylmethylidene) hydrazine carbothioamide (FMHC) as an inhibitor for corrosion of mild steel in 0.5 M H2SO4 is reported. Experiments were conducted at various temperatures (303–323 K) by adopting potentiodynamic polarization and electrochemical impedance spectroscopy. Readings obtained demonstrated that percentage inhibition efficiency (% IE) improved with the upsurge in the concentration of FMHC, while it decreased with a rise in temperature. The highest % IE observed was 60% for 2.5 × 10–4 M FMHC at 303 K. FMHC worked moderately as a mixed inhibitor. FMHC obeyed the Langmuir model of adsorption and the mode of adsorption was physisorption on the mild steel surface which was further endorsed by examining the surface using the scanning electron microscope. A clear insight into the mechanistic features of corrosion inhibition by using FMHC was acquired. Calculation of activation parameters helped to suggest an appropriate mechanism for the adsorption of FMHC on mild steel through quantum chemical calculations using density functional theory (DFT).

Graphical abstract

Electrochemical, spectroscopic and theoretical studies for acid corrosion of zinc using glycogen

The objective of the work is to introduce and establish anticorrosion capabilities of a novel biopolymer glycogen (GLY) against sulfamic acid (NH2SO3H) induced corrosion of zinc. The corrosion and inhibition studies were done by electrochemical techniques such as potentiodynamic polarization (PDP) measurements and electrochemical impedance spectroscopy technique (EIS). Conditions were optimized to get maximum inhibition efficiency by varying the concentration of the inhibitor in the temperature range of 303–323 K. Activation and thermodynamic parameters were evaluated and discussed in detail. Suitable adsorption isotherm was proposed to fit the experimental results. Scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and atomic force microscopy (AFM) studies were performed before and after the addition of inhibitor. Adsorption of inhibitor was further confirmed by UV–Visible spectroscopy. Quantum chemical calculations were done to establish the correlation between the structure of the inhibitor and its inhibition efficiency. Energy of HOMO, LUMO, energy gap ∆E, dipole moment (µ) Mullikan charges were calculated. Different theoretical factor descriptors like the hardness (η), and softness (σ) electronegativity (χ), global electrophilicity (ω), nucleophilicity (ε) and fraction of electron transferred (ΔN) were calculated. Inhibition efficiency of glycogen increased with increase in its concentration and with temperature. Maximum efficiency of 72% could be achieved for the addition of 0.05 g L−1 of GLY at 323 K. Results were fitted into Langmuir adsorption iostherm. The surface of the metal turned visibly smoother in the presence of GLY. In addition the EDX studies showed increase in carbon content which re-affirmed the adsorption of GLY on the metal surface. The density functional theory (DFT) based theoretical studies supported the experimental observations.

9-Substituted acridines as effective corrosion inhibitors for mild steel: electrochemical, surface morphology, and computational studies

The inhibition performance and mechanism of mild steel in hydrochloric acid for 9-substituted acridines were studied for the first time.

Experimental and DFT studies on the ultrasonic energy-assisted extraction of the phytochemicals of Catharanthus roseus as green corrosion inhibitors for mild steel in NaCl medium

Catharanthus roseus (Apocynaceae family) extract is rich in organic phytochemicals such as alkaloids, polyphenolic compounds, and flavonoids. It contains several functional entities such as fused heterocycles, and hydroxyl and carbonyl groups, which could be useful for corrosion inhibition of mild steel in NaCl environments. In the present work, ultrasonic energy was used to obtain the ethanolic extracts of root and stem which were then tested as corrosion inhibitors for mild steel in the presence of 3.5% NaCl. The corrosion inhibition process was studied by UV-visible spectroscopy, Fourier transform infrared spectroscopy, atomic force microscopy, weight loss, and electrochemical methods. After immersing in the corrosive medium, the microstructures of mild steel were investigated by scanning electron microscopy, X-ray diffraction, and ellipsometry. The extract of C. roseus showed excellent adsorption on mild steel surface as confirmed by DFT calculations. The results indicate that the extract of C. roseus acts as a mixed type corrosion inhibitor, where the stem extract is the most efficient inhibitor in 3.5% NaCl solution possibly due to the higher active area of stem phytochemicals.

C. roseus phytochemicals are physisorbed on the 111 Fe surface, and the oxygen non-bonding electron chemisorbed on the polarized state 111 Fe surface.

New, Amino Acid Based Zwitterionic Polymers as Promising Corrosion Inhibitors of Mild Steel in 1 M HCl

The zwitterionic monomers, N,N’-diallylamino propanephosphonate and amino acid residual N,N’-diallyl-l-methionine hydrochloride were synthesized, with excellent yields. These monomers were utilized in the preparation of zwitterionic homo and co-cyclopolymers 5–7 in aqueous solution using 2,2′-azobis (2-methylpropionamidine) dihydrochloride as an initiator. The polymers were characterized by FT-IR, NMR, and TGA. The performance of these synthesized polymers on mild steel in acidic solution was investigated by gravimetric method, Tafel extrapolation, linear polarization resistance, and electrochemical impedance spectroscopy. At 313 K, the maximum inhibition efficiencies of corrosion inhibitors 5–7 at 4.50 × 10−4 mol L−1 were found to be 85.2%, 83.3%, and 99.5%, respectively. The inhibition efficiencies obtained from gravimetric weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopy measurements were in good agreement. Different adsorption isotherms were also explored to find the best fit, and found to obey Langmuir adsorption isotherm. The thermodynamic parameters, such as activation energy (Ea), standard enthalpy of activation (ΔH*), standard entropy of activation (ΔS*), adsorption–desorption equilibrium constant (Kads), and standard free energy of adsorption (ΔGoads), were determined. Electrochemical data indicated that the zwitterionic copolymer 7 acts as a mixed type inhibitor under the influence of anodic control. The surface morphology of mild steel corrosion was evaluated without and with corrosion inhibitors by AFM, SEM-EDX, and XPS, which confirmed the adsorption of inhibitor molecules on the metal surface.

Highly effective inhibition of mild steel corrosion in HCl solution by using pyrido[1,2-a]benzimidazoles

Pyrido[1,2-a]benzimidazoles are reported herein for the first time as effective inhibitors of mild steel corrosion in hydrochloric acid.

Synergistic effect of 1-(2,5-dioxoimidazolidin-4-yl)urea and Tween-80 towards the corrosion mitigation of mild steel in HCl

The inhibition performance and synergistic inhibition effect of DMU with Tween-80 on the corrosion of mild steel in 1 M HCl was studied for the first time.

Bispyranopyrazoles as Green Corrosion Inhibitors for Mild Steel in Hydrochloric Acid: Experimental and Theoretical Approach

In the present study, we have synthesized two novel corrosion inhibitors BP-1 and BP-2 and evaluated their corrosion inhibition property on mild steel (MS) in acid solution through weight loss and electrochemical corrosion techniques. The corrosion test results reveal that both compounds inhibit corrosion by an adsorption mechanism and display inhibition efficiency more than 95% at a low concentration of 1.72 × 10^-4 M. From the surface analysis of the protective film on MS, it was corroborated that adsorption of inhibitor molecules occurred on the MS surface through chemisorption, which further suppresses the corrosion rate. Density functional theory simulated data helps correlate the experimental trend with the theoretical study.

Indolizine quaternary ammonium salt inhibitors part II: a reinvestigation of an old-fashioned strong acid corrosion inhibitor phenacyl quinolinium bromide and its indolizine derivative

Anti-corrosion inhibition was dramatically improved by transforming heterocyclic ammonium inhibitors into their dimer indolizine derivatives.

A combination of experiment and theoretical methods to study the novel and low-cost corrosion inhibitor 1-hydroxy-7-azabenzotriazole for mild steel in 1 M sulfuric acid

1-Hydroxy-7-azabenzotriazole (HOAT) was explored via experimental and theoretical computation methods as a corrosion inhibitor for mild steel in 1 M sulfuric acid. These data indicate that HOAT has good ability to suppress corrosion of the mild steel, with ideal agreement with between experimental and computational results. Besides, the electrochemical experiments show that HOAT is a mixed-type corrosion inhibitor for mild steel in 1 M H₂SO₄. Furthermore, HOAT adsorption on the surface of steel conforms to the Langmuir isotherm model. Finally, computational simulation was executed to deeply investigate the mechanism to HOAT inhibition corrosion of steel.

1-Hydroxy-7-azabenzotriazole (HOAT) was explored via experimental and theoretical computation methods as a corrosion inhibitor for mild steel in 1 M sulfuric acid.