Scielo RSS http://scielo.pt/rss.php?pid=0872-190420150003&lang=pt vol. 33 num. 3 lang. pt http://scielo.pt/img/en/fbpelogp.gif http://scielo.pt http://scielo.pt/scielo.php?script=sci_arttext&pid=S0872-19042015000300001&lng=pt&nrm=iso&tlng=pt The effect of linseed oil (LO) on the corrosion of carbon steel in 1 M HCl solution was investigated using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) technique and weight loss measurements. The inhibiting action increases with the concentration of the tested inhibitor. The highest efficiency (98.2%) is obtained at 3g/L of LO. The influence of temperature on the corrosion behavior of carbon steel in 1 M HCl, with the addition of LO was also studied. The obtained data from EIS measurements were analyzed to model the corrosion inhibition process through an appropriate equivalent circuit model; a constant phase element (CPE) has been used. Polarization measurements show also that LO acts as a good mixed inhibitor. The inhibition process is attributed to the formation of an adsorbed film of the inhibitor on the metal surface which protects the metal against corrosion. LO is adsorbed on the steel surface according to a Langmuir isotherm adsorption model. The results obtained showed that the linseed oil could serve as an effective green inhibitor of the corrosion of carbon steel in hydrochloric acid medium. http://scielo.pt/scielo.php?script=sci_arttext&pid=S0872-19042015000300002&lng=pt&nrm=iso&tlng=pt A new quaternary Ni-Fe-P-C composite coating was deposited on copper substrates by an electrodeposition process. The morphology, structure and composition of the prepared electrode were characterized using scanning electron microscopy (SEM), X- ray diffraction (XRD) pattern, and energy dispersive X-ray spectroscopy (EDX). The activity of the composite coating toward hydrogen evolution reaction (HER) was evaluated on the basis of the steady-state polarization Tafel curves and electrochemical impedance spectroscopy (EIS) in 1 M NaOH at temperature of 298 K. The experimental results revealed that the HER activity of the Ni-Fe-P-C coatings was enhanced compared with both ternary coatings of Ni-P-C and Ni-Fe-C. The source of its activity was found from its high surface area and its intrinsic properties. It was sufficient to assume the Volmer-Heyrovsky mechanism with the Heyrovsky reaction as the rate- determining step to explain the experimental data. Besides the high electrocatalytic activity, excellent chemical and electrochemical stability were observed for Ni-Fe-P-C composite coating toward the HER in 1 M NaOH at 298 K. http://scielo.pt/scielo.php?script=sci_arttext&pid=S0872-19042015000300003&lng=pt&nrm=iso&tlng=pt The present research article deals with the study of corrosion behavior of Ni-P-TiO2 composite coating. The TiO2 composite coating is deposited on the mild steel substrate. Corrosion behavior of the TiO2 composite coatings after heat treatment at various annealing temperatures (300 °C, 400 °C, and 500 °C) is evaluated with the help of potentiodynamic polarization test using 3.5% NaCl solution. The electrochemical parameters, corrosion potential (Ecorr) and corrosion current density (Icorr), are optimized for maximum corrosion resistance using Taguchi based grey relational analysis. The coating parameters, namely, nickel sulphate, sodium hypophosphite, concentration of TiO2 particles and annealing temperature are considered as main design factors. The analysis of variance (ANOVA) revealed that the annealing temperature and concentration of TiO2 particles have significant influence on the corrosion behavior of the composite coating. The microstructure characterization of the coating is conducted using scanning electron microscopy, energy dispersive X-ray analysis and X-ray diffraction analysis. The Ni-P-TiO2 composite coating exhibits nodular structure with uniform incorporation of titanium particles and converts into the crystalline structure after heat treatment. http://scielo.pt/scielo.php?script=sci_arttext&pid=S0872-19042015000300004&lng=pt&nrm=iso&tlng=pt The aim of present study is to establish the not known divalent state of praseodymium and samarium in non-aqueous medium at 298.15 K and atmospheric pressure. Potentiostatic and galvanostatic methods were used to characterize the divalent states of both lanthanides. Under the specified experimental conditions, samarium and praseodymium showed two reduction steps at glassy carbon electrode in non-aqueous medium. Cathodic and corresponding anodic peak potential and peak currents were calculated for samarium and praseodymium ions at different scan rates. The results also suggest that the scan rate has great influence on the behaviour of both lanthanides. Diffusion coefficient (D × cm² s-1) and heterogeneous forward rate constant (kºfh × cm s-1) have been evaluated. Transition time (τ) has also been evaluated for Pr(III)/Pr(II), Pr(II)/Pr(0) coupled systems, suggesting that the system is approaching from irreversible with increasing the scan rates. The effects of changing the scan rate and donor number on the electrochemical behavior of both lanthanides have been examined at 298.15 K and atmospheric pressure. http://scielo.pt/scielo.php?script=sci_arttext&pid=S0872-19042015000300005&lng=pt&nrm=iso&tlng=pt Concrete is one of the most widely used engineering materials for construction. Its durability is a major problem affecting the service life of the engineering structures. Various technologies such as cathodic protection and the use of corrosion inhibitors are used to improve the durability of reinforced concrete. Various organic and inorganic inhibitors, and also extracts of natural products have been used as corrosion inhibitors. Corrosion resistance of rebars has been evaluated by electrochemical studies such as polarization study and AC impedance spectra. The protective films formed on the metal surface have been analyzed by NMR, FTIR spectra, SEM, AFM and XRD.