Inhibitive properties, thermodynamic, kinetics and quantum chemical calculations of polydentate Schiff base compounds as corrosion inhibitors for iron in acidic and alkaline media

Synthesis, characterization, biological studies and DFT study of Schiff Bases and their complexes derived from aromatic diamine compounds with cobalt (II)

Based on vanillin and diamine compounds (ortho phenylene diamine, meta phenylene diamine, 3,4- diamine toluene), derivation of two new Schiff base ligands (L1 and L2) was done, after which synthesis and treatment with Co (II) chloride was performed at a metal-to-ligand ratio of 1:1 to get two new complexes, i.e. [CoL3(H2O)2]Cl2 and [CoL1(H2O)2]Cl2. These complexes and ligands were characterized by employing NMR, IR, atomic absorption, UV visible absorption, molecular weight determination, molar conductance, and magnetic measurement techniques. As per the data, the ligands were found to be bidentate ligands that were linked to two azomethine nitrogen sites. It was suggested that these complexes were paramagnetic electrolyte compounds that possessed coordination number four. Screening of the ligands and metal complexes was done to assess their antimicrobial activities against gram-negative and gram-positive bacteria, which was found to show biological activity. Calculations using quantum chemistry were done to examine the molecule geometry. The investigation includes several quantum chemical characteristics derived from frontier molecular orbitals. Keywords: Schiff bases, transition metal complexes, vanillin, diamine aromatic compounds, antibacterial activity, DFT study.

Mannich Base as an Efficient Corrosion Inhibitor of AA6061 in 0.5 M HCl: Electrochemical, Surface Morphological and Theoretical Investigations

The inhibition action of a Mannich base, N-(1- morpholinobenzyl) semicarbazide (MBS), was examined on AA6061 corrosion in 0.5 M HCl solution at varied temperatures (303 to 323 K). The testing was performed by potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) techniques. The inhibition performance of MBS was improved with an increment in its concentration (0.01–2.56 mM) and temperature rise (303 to 323 K). MBS showed a mixed inhibitor behavior at all concentrations and temperatures range studied. MBS displayed the highest inhibition efficiency of 98% at 2.56 mM and 323 K. Inhibitor followed mixed adsorption on the alloy surface and obeyed the Langmuir isotherm model. The results obtained from the EIS were in good agreement with that of the PDP results. An appropriate mechanism was proposed for the corrosion inhibition of AA6061. Inhibitor molecules adsorption on alloy surface was confirmed by surface morphology testing by a scanning electron microscope (SEM) and atomic force microscope (AFM). Theoretical studies using density-functional theory (DFT) confirmed the experimental results.

Inhibitory influence of cationic Gemini surfactant on the dissolution rate of N80 carbon steel in 15% HCl solution

Strong acids are commonly used in petroleum wells to remove scale layers from the surface of N80 C-steel pipe. The corrosive effects of these acids, on the other hand, pose a significant risk to C-steel pipes. For the first time, we discovered the anti-corrosion properties of cationic Gemini surfactant, 1,2-bis(dodecyldimethylammonio) ethane dibromide (DMAEB), for N80 C-steel pipe in acid washing solution (15.0% HCl). The DMAEB, in particular, can reduce the corrosion rate of N80 C-steel by approximately 97%. DMAEB molecules work as a mixed-type corrosion inhibitor, according to electrochemical results. The DMAEB demonstrated a high inhibition effect at high temperatures, as well as high activation energy against the corrosion process. DMAEB's significant performance is primarily due to physical adsorption on the N80 C-steel surface, as confirmed by adsorption isotherms, SEM, EDX, FT-IR, and theoretical studies. Our findings shed new light on the use of Gemini surfactants as corrosion inhibitors in petroleum wells.

Quantum chemical and experimental evaluation of the inhibitory action of two imidazole derivatives on mild steel corrosion in sulphuric acid medium

The adsorption and corrosion inhibition properties of two imidazole derivatives namely, 2-(4-chlorophenyl)-1,4,5-triphenyl-1H-imidazole (IM-Cl) and 1,4,5-triphenyl-2-(p-tolyl)-1H-imidazole (IM-CH₃) for mild steel in 0.5 M H₂SO₄ solution are studiedby electrochemical and computational calculations. The results obtained from the electrochemical methods show that IM-Cl and IM-CH₃imparted high resistance and behave as mixed type inhibitors. Inhibition efficiency (IE %) increases with the increase of inhibitors concentration to attain 96 % and 91% at 10⁻³ M of IM-Cl and IM-CH₃ respectively. EISdatais analyzed to model the inhibition process through appropriate equivalent circuit model. Thermodynamic and kinetic parameters controlling the adsorption process are calculated and discussed. DFT calculations are carried out at the B3LYP levels of theory with 6-31G (d,p) basis stein gas and aqueous phase for neutral and protonated forms. Quantum chemical calculations section of the study provides enough calculation and discussion on the relationship between corrosion inhibition and global reactivity descriptors.

Anticorrosive Effects of Some Thiophene Derivatives Against the Corrosion of Iron: A Computational Study

It is known that iron is one of the most widely used metals in industrial production. In this work, the inhibition performances of three thiophene derivatives on the corrosion of iron were investigated in the light of several theoretical approaches. In the section including DFT calculations, several global reactivity descriptors such as E_HOMO, E_LUMO, ionization energy (I), electron affinity (A), HOMO-LUMO energy gap (ΔE), chemical hardness (η), softness (σ), as well as local reactivity descriptors like Fukui indices, local softness, and local electrophilicity were considered and discussed. The adsorption behaviors of considered thiophene derivatives on Fe(110) surface were investigated using molecular dynamics simulation approach. To determine the most active corrosion inhibitor among studied thiophene derivatives, we used the principle component analysis (PCA) and agglomerative hierarchical cluster analysis (AHCA). Accordingly, all data obtained using various theoretical calculation techniques are consistent with experiments.