Xanthione: A new and effective corrosion inhibitor for mild steel in sulphuric acid solution

The adsorption and inhibition effect of xanthione (XION) on mild steel in 0.5 M H₂SO₄ at 303–333 K were studied using gravimetric and UV–visible spectrophotometric methods. The results obtained show that XION acts as an effective corrosion inhibitor for mild steel in sulphuric acid and inhibition efficiency reaches 98.0% at a very low inhibitor concentration of 10 μM. Inhibition efficiency was found to increase with increase in XION concentration but decreased with temperature suggesting physical adsorption mechanism. Arrhenius law and its transition equation lead to estimate the activation parameters of the corrosion process. XION inhibits the corrosion of mild steel effectively at moderate temperature and adsorbs according to the Langmuir isotherm. Thermodynamic parameters governing the adsorption process have been calculated and discussed. The UV–visible absorption spectra of the solution containing the inhibitor after the immersion of mild steel specimen indicate the formation of a XEN–Fe complex. Attempt to correlate the molecular structure to quantum chemical indices was made using density functional theory (DFT).     

Spondias mombin L. as a green corrosion inhibitor for aluminium in sulphuric acid: Correlation between inhibitive effect and electronic properties of extracts major constituents using density functional theory

The inhibition of aluminium in 0.5 M H₂SO₄ by extracts of Spondias mombin L. was investigated using the standard gravimetric technique at 30–60 °C. The trend of inhibition efficiency with temperature was used to propose the mechanism of inhibition. It was found that the S. mombin L. extract acts as an inhibitor for acid-induced corrosion of aluminium. Inhibition efficiency (%I) of the extract increased with an increase in concentration of the S. mombin L. extract but decreased with temperature. Furthermore, inhibition efficiency (%I) synergistically increased on addition of potassium iodide. Inhibitor adsorption characteristics were approximated by Langmuir adsorption isotherm at all the concentrations and temperatures studied. The mechanism of physical adsorption is proposed from the trend of inhibition efficiency with temperature and from the calculated values of Gibbs free energy, activation energy and heat of adsorption. Quantum chemical calculations were performed using the density functional theory at B3LYP/6-31G (d) level of theory to find out whether a clear link exists between the inhibitive effect of the extract and the electronic properties of its main constituents.     

Adsorption and corrosion inhibition characteristics of strawberry fruit extract at steel/acids interfaces: experimental and theoretical approaches

Ionics - The adsorption and corrosion inhibition behavior of strawberry fruit extract at steel/1 M HCl and steel/0.5 M H2SO4 interfaces were investigated using gravimetric and...     

Experimental and theoretical investigations of adsorption characteristics of itraconazole as green corrosion inhibitor at a mild steel/hydrochloric acid interface

The adsorption and inhibition effect of itraconazole (ICZ) on mild steel in 0.5?M HCl at 303?C333?K was studied using gravimetric and quantum chemical methods. The adsorption of ICZ has been tested thermodynamically and was found to be mainly a physical adsorption mechanism and weak chemisorption. The activation and thermodynamic functions (such as E _a, $ \Updelta H^{*} ,\,\Updelta G_{\text{ads}}^{\text{o}} $ ) of dissolution and adsorption processes have been evaluated and discussed. The analyses of the results obtained showed that ICZ inhibits the corrosion of mild steel effectively at moderate temperatures and adsorbs according to the Temkin adsorption isotherm. An attempt to correlate the molecular structure to quantum chemical indices was made using a semi-empirical (PM3) method. Results of the theoretical study indicate that nitrogen and oxygen atoms (O10, O13, N17, N19, O21, N28, N42, N43, and O45) were the reactive sites.     

Experimental, quantum chemical calculations, and molecular dynamic simulations insight into the corrosion inhibition properties of 2-(6-methylpyridin-2-yl)oxazolo[5,4-f][1,10]phenanthroline on mild steel

2-(6-Methylpyridin-2-yl)oxazolo[5,4-f][1,10]phenanthroline (MOP) was synthesized and characterized by elemental analysis and Fourier-transform infrared (FT-IR), ¹H nuclear magnetic resonance (NMR), and ¹³C NMR spectra. MOP was evaluated as a corrosion inhibitor for carbon steel in 0.5 M H₂SO₄ solution using the standard gravimetric technique at 303–333 K. Quantum chemical calculations and molecular dynamic (MD) simulations were applied to analyze the experimental data and elucidate the adsorption behavior and inhibition mechanism of MOP. Results obtained show that MOP is an efficient inhibitor for mild steel in H₂SO₄ solution. The inhibition efficiency was found to increase with increase in MOP concentration but decreased with temperature. Activation parameters and Gibbs free energy for the adsorption process using statistical physics were calculated and discussed. The adsorption of MOP was found to involve both physical and chemical adsorption mechanisms. Density functional theory (DFT) calculations suggest that nitrogen and oxygen atoms present in the MOP structure were the active reaction sites for the inhibitor adsorption on mild steel surface via donor–acceptor interactions between the lone pairs on nitrogen and oxygen atoms together with the π-electrons of the heterocyclic and the vacant d-orbital of iron atoms. The adsorption of MOP on Fe (1 1 0) surface was parallel to the surface so as to maximize contact, as shown in the MD simulations. The experiments together with DFT and MD simulations provide further insight into the mechanism of interaction between MOP and mild steel.     

Fluconazole as an inhibitor for aluminium corrosion in 0.1 M HCl

The interfacial behavior of fluconazole (FLC) between aluminium and hydrochloric acid has been investigated by using weight loss technique at 30–50 °C. The results showed that fluconazole is an excellent corrosion inhibitor for aluminium in acidic medium. Inhibition efficiency increased with increase in the concentrations of fluconazole but decreased with rise in temperature. The adsorption of the inhibitor on the aluminium surface is found to accord with Temkin adsorption isotherm. Some thermodynamic and activation parameters have been calculated and analysed. The mechanism of physical adsorption is proposed from the values of E_a and obtained. The correlation of inhibition effect and molecular structure of fluconazole was then discussed by quantum chemistry study to further provide insight into the mechanism of the inhibitory action.     

Adsorption behavior and corrosion inhibitive potential of xanthene on mild steel/sulphuric acid interface

The inhibition of xanthene (XEN) on the corrosion of mild steel in 0.5 M H₂SO₄ was studied by gravimetric and UV–visible spectrophotometric methods at 303–333 K. Results obtained show that XEN act as inhibitor for mild steel in H₂SO₄ solution. The inhibition efficiency was found to increase with increase in XEN concentration but decreased with temperature. Activation parameters and Gibbs free energy for the adsorption process using Statistical Physics were calculated and discussed. The corrosion process in 0.5 M H₂SO₄ in the absence and presence of XEN follows zero-order kinetics. The UV–visible absorption spectra of the solution containing the inhibitor after the immersion of mild steel specimen indicate the formation of a XEN–Fe complex. Quantum chemical calculations using DFT were used to calculate some electronic properties of the molecule in order to ascertain any correlation between the inhibitive effect and molecular structure of xanthene.