Giuseppe Quartarone

Inhibition of copper corrosion by isatin in aerated 0.5 M H2SO4

The corrosion inhibition of commercial copper by means of isatin was studied in aerated 0.5 M H2SO4 in the temperature range 25–55 °C using weight-loss, potentiodynamic and spectrophotometric tests, and determination of double layer capacitance. Inhibition efficiencies up to 94% in the concentration range of 1×10−4–7.5×10−3 M of isatin were obtained. The corrosion rates estimated with weight-loss measurements were higher than those correspondingly determined with the potentiodynamic test, especially at higher concentrations of inhibitor. This is in accord with other researches that have pointed out the limitation of the Tafel line extrapolation method in the determination of corrosion rates. The kinetics of cuprous and cupric ion formation and UV–visible spectra support the formation hypothesis of a complex between copper and isatin. The adsorptive behaviour of isatin on copper 0.5 M H2SO4 was also investigated.

Using Indole to Inhibit Copper Corrosion in Aerated 0.5 M Sulfuric Acid

Abstract Inhibition of copper corrosion in aerated 0.5 M sulfuric acid (H2SO4) solutions containing various concentrations of indole was studied in the temperature range from 25°C to 55°C using pot...

In-Situ Contact Electrical Resistance Technique for Investigating Corrosion Inhibitor Adsorption on Copper Electrodes

Abstract Traditional electrochemical tests and the contact electrical resistance technique (CER) were used to investigate the effect on corrosion of pure copper (99.999 wt%) of adding benzotriazole...

Sigma Phase Intergranular Corrosion Effects in Austenitic Welds Containing Ferrite

Abstract It has been suggested that the sigma phase and its preliminary phases are responsible for intergranular corrosion of molybdenum-containing austenitic stainless steels in such environments ...

Study of inhibition mechanism and efficiency of indole-5-carboxylic acid on corrosion of copper in aerated 0,5M H2SO4

Abstract Inhibition of the corrosion of copper in aerated 0·5M sulphuric acid solutions containing various concentrations of indole-5-carboxylic acid was studied in the temperature range 25–55°C using potentiodynamic curves (Tafel lines), weight loss, analytical methods, and determination of double layer capacitance. The corrosion rates reveal good corrosion inhibition, up to 95% in the concentration range of 1 × 10-4–4 × 10-3M. Tafel anodic slopes in inhibited acid solutions are considerably higher than those in uninhibited acid solutions. This points to a change in the corrosion mechanism of copper in the presence of indole-5-carboxylic acid. Under these conditions, copper could electro-oxidise primarily to Cu+ rather than to Cu2+, forming slightly soluble [Cu–(indole-5-carboxylic)n ]+(ads) complexes. Corrosion rates determined by the weight loss method in both the absence and presence of inhibitor are much higher (on average by a factor of about 6) than those obtained with the potentiodynamic method. This points to a limitation of the Tafel line extrapolation method in corrosion rate determination. The double layer capacitance–potential curves indicate considerable adsorption of the inhibitor over a wide potential range (-600 to +200 mV with regard to Ecorr ).

Corrosion Inhibition of Copper in Aerated 0.5 M Sulfuric Acid by Indole-2-Carboxylic Acid

Abstract The inhibiting action of indole-2-carboxylic acid (C9H7NO2) on the corrosion of commercial copper in aerated 0.5 M sulfuric acid (H2SO4) has been investigated in the temperature range from 25°C to 55°C by weight loss, potentiodynamic and analytical tests, and the determination of double-layer capacitance. The results have revealed a good inhibitor efficiency, up to 98% in the concentration range from 1 × 10−4 M to 4 × 10−3 M. Indole-2-carboxylic acid has been found to act as a mixed inhibitor. The kinetics of Cu+ and Cu2+ formation that followed in 72 h of gravimetric testing shows that indole-2-carboxylic acid probably affects the corrosion reaction mechanism through complexes with cuprous ions. The corrosion rates determined through weight-loss measurements are much higher than those obtained with potentiodynamic tests. This is in accord with other researchers who have found limitations to the extrapolation of polarization curves (and to the theory of mixed potentials) in the determination of c...

Quantum Chemical Investigation on Indole: Vibrational Force Field and Theoretical Determination of Its Aqueous pKa Value

Indole and its derivatives are molecules which play important roles in different fields, from biology to pharmacology. Here we report a thorough investigation on the anharmonic force fields of indole as well as the ab initio determinations of its gas phase basicity and aqueous pK(a) value. For the geometry optimizations, the calculations have been performed using both density functional (DFT) and second-order Møller-Plesset (MP2) levels of theory employing different basis sets. Anharmonic force fields have been obtained employing both the B3LYP and the B97-1 functionals and an hybrid approach: the best agreement to the experimental data has been determined employing the B3LYP functional combined with the recently developed N07D basis set (mean unsigned error, MUE, of 5.1 cm(-1) and a root-mean-square error, RMSE, of 7.2 cm(-1)). Gas phase basicity and proton affinity have been computed employing several computational schemes, namely the G3 and G4 Gaussian models, the complete basis set (CBS) extrapolation methods of Petersson and co-workers, several DFT calculations, and different hybrid extrapolation schemes based on combining single-point energy calculations performed at MP2 as well as at coupled cluster level of theory with single, double and perturbative triple excitations, CCSD(T). Regarding the aqueous pK(a) computations, two implicit solvation models (SMD and SM8) have been employed to determine the free energy of solvation and the corresponding pKa value.

Acid Catalyzed Direct-Amidation–Dehydrocyclization of 2-Hydroxy-acetophenones to Benzoxazoles by a One-Pot Sustainable Synthesis

A series of 2-methyl-benzoxazoles have been synthesized starting from 2-hydroxy-acetophenones via a one-pot three steps reaction. Hydroxylamonium salt has been used as amidation agent. The reaction occurs with different anions, but the best results is achieved with hydroxylamonium hydrchloride. Despite the number of consecutive stages, the reaction is highly selective. Mild reaction conditions and various solvents can be used, but trifluoroacetic acid is the preferred. Almost, complete recovery of the trifluoroacetic acid can be achieved by vacuum distillation. The role of trifluoroacetic acid, as well as, of the hydroxylamonium salt suggests a cooperative effect leading to high selective formation of 2-methyl-benzoxazoles.Graphical AbstractOne-pot TFA catalyzed synthesis of benzoxazoles starting from 2-hydroxyacetophenones.

New magnetically recoverable palladium-based catalysts active in the alkoxycarbonylation of iodobenzene

Abstract New magnetically recoverable catalysts have been synthesized by deposition of 1% palladium (Pd)-metal on the polymer poly(1-oxo-trimethylene), containing 15% of magnetite. The magnetite allows the complete recovery of the catalyst with the simple application of an external magnetic field. The activity of such a catalyst has been studied under phosphine-free conditions in the alkoxycarbonylation of iodobenzene to the corresponding benzoic acid esters.

New passivating pastes for stainless steel without nitric acid

Handled stainless steel (SS) structures often need accurate passivating treatments before use. Until now the most frequently used passivating pastes have been based on nitric (fluoridric) acid and, as a result, are responsible for consequent environmental problems. This work addresses the SS passivation quality of two low environmental impact pastes, based on peroximonosulfate (P2) or sodium perborate (P3). Tests were conducted on various materials using electrochemical tests (cyclic voltammetry, anodic potentiostatic transients, open-circuit potential (E) decay), Microscopic and Inductively Coupled Plasma (ICP) measurements. The results, when compared with those obtained on the same materials by using a conventional nitric acid paste (P1), indicate that the proposed pastes P2 and P3 are time stable, non toxic and as efficient as the P1 paste. Moreover, the protection of the tested SS can be further enhanced by adding small amounts of citric acid to, in particular, the P3 paste.