Inhibitive effect of sodium (E)-4-(4-nitrobenzylidenamino) benzoate on the corrosion of some metals in sodium chloride solution

The inhibition performance of a novel anionic carboxylic Schiff base, sodium (E)-4-(4-nitrobenzylideneamino)benzoate (SNBB), was investigated for various metals, namely low carbon steel F111, pure iron and copper, in neutral 10 mM NaCl solution. Potentiodynamic polarization, scanning vibrating electrode technique (SVET), quantum chemical (QC) calculation, and molecular dynamics (MD) simulation were employed. The potentiodynamic polarization data showed that SNBB acts as an effective corrosion inhibitor for both iron and F111 steel, but it is not effective for the copper. In situ spatially-resolved SVET maps evidenced a major change in surface reactivity for Fe and F111 steel immersed in 10 mM aqueous solution in the absence and in the presence of SNBB. Featureless ionic current density distributions were recorded in the presence of SNBB at both their spontaneous open circuit potential (OCP) and under mild anodic polarization conditions, while major ionic flows were monitored above the metals in the absence of SNBB. On the basis of computer simulations, it is proposed that SNBB produces a stable chelate film on iron and steel surfaces that accounts for the good corrosion inhibition efficiency observed. The different inhibition efficiencies of SNBB molecules on the iron and copper was attributed to the special chemical structure of SNBB molecule and its different chelation ability with the released metal ions on the metal surface. The QC calculations also confirmed the high corrosion inhibition efficiency of SNBB. The MD simulation indicated higher binding energy of SNBB on iron surface compared to that of copper surface. The interaction mode of SNBB on iron and F111 steel surfaces corresponds to a mixed chemical and physical adsorption, and it obeys the Langmuir isother

ac impedance, X-ray photoelectron spectroscopy and density functional theory studies of 3,5-bis(<i>n</i>-pyridyl)-1,2,4-oxadiazoles as efficient corrosion inhibitors for carbon steel surface in hydrochloric acid solution

The corrosion inhibition properties of a new class of oxadiazole derivatives, namely 3,5-bis(n-pyridyl)-1,2,4-oxadiazoles (n-DPOX) for C38 carbon steel corrosion in 1 M HCl medium were analysed by electrochemical impedance spectroscopy (EIS). An adequate structural model of the interface was used and the values of the corresponding parameters were calculated and discussed. The experimental results showed that these compounds are excellent inhibitors for the C38 steel corrosion in acid solution and that the protection efficiency increased with increasing the inhibitors concentration. Electrochemical impedance data demonstrate that the addition of the n-DPOX derivatives in the corrosive solution decreases the charge capacitance and simultaneously increases the function of the charge/discharge of the interface, facilitating the formation of an adsorbed layer over the steel surface. Adsorption of these inhibitors on the steel surface obeys to the Langmuir adsorption isotherm. X-ray photoelectron spectroscopy (XPS) and the thermodynamic data of adsorption showed that inhibition of steel corrosion in normal hydrochloric solution by n-DPOX is due to the formation of a chemisorbed film on the steel surface. Quantum chemical calculations using the Density Functional Theory (DFT) and the Quantitative Structure Activity Relationship (QSAR) approach were performed on n-DPOX derivatives to determine the relationship between molecular structure and their inhibition efficiencies. The results of the quantum chemical calculations and experimental inhibition efficiency were subjected to correlation analysis and indicate that their inhibition effect is closely related to EHOMO, ELUMO, and dipole moment (μ)

Improvement of corrosion resistance of carbon steel in hydrochloric acid medium by 3,6-bis(3-pyridyl)pyridazine

Corrosion inhibition of carbon steel in normal hydrochloric acid solution at 30°C by new pirydazine derivative, namely 3,6-bis(3-pyridyl) pyridazine (3-PYP) has been studied by a series of known techniques such as weight loss, polarisation and electrochemical impedance spectroscopy (EIS). The experimental results have showed that this organic compound revealed a good corrosion inhibition and that the inhibition efficiency is increased with the inhibitor concentration. Potentiodynamic polarisation suggested that it is a mixed type of inhibitor. Two time constants determined by the charge-transfer and the adsorption of the inhibitor, respectively, can be readily outlined. The adsorption of 3-PYP on the carbon steel surface, in 1 M HCl solution, obeyed to the Temkin's isotherm with a very high negative value of the standard Gibbs free energy of adsorption δG°ads (chemisorption). Quantum chemical calculations and X-ray photoelectron spectroscopy (XPS) analysis were carried out to establish the mechanism of corrosion inhibition of carbon steel in 1 M HCl medium in the presence of 3,6-bis(3-pyridyl)pyridazine (3-PYP)

Synthesis, Spectroscopy Studies, and Theoretical Calculations of New Fluorescent Probes Based on Pyrazole Containing Porphyrins for Zn(II), Cd(II), and Hg(II) Optical Detection

New pyrazole porphyrin conjugates were successfully prepared from a reaction of beta-porphyrin chalcone derivatives with phenylhydrazine in acetic acid followed by an oxidative step. This fast and efficient synthetic approach provided the expected compounds in yields up to 82%. The sensing ability of the new porphyrin-pyrazole derivatives to detect the metal ions Ag+, Na+, K+, Mg2+, Ca2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+, Pb2+, and Cr3+ was studied by spectrophotometric and spectrofluorimetric titrations. In the presence of Zn2+, the conjugates exhibit changes in the emission spectra that are desired for a ratiometric-type fluoroionophoric detection probe. The studies were extended to gas phase, where the pyrazole porphyrin conjugates show ability to sense metal ions with high selectivity toward Cu2+ and Ag+, and in poly(methyl methacrylate) doped films with promising results for Zn2+ detection