Portugaliae
Electrochimica Acta

The inhibitive effect of Lupine extract on the corrosion of etched and non-etched aluminum in aqueous solution of 0.1 M HCl was investigated at 30 ºC by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and optical microscopic techniques. Potentiodynamic polarization curves indicated that Lupine extract acts as anodic type inhibitor. EIS measurements showed that the charge transfer resistance and consequently the inhibition efficiency increase with increasing concentration of Lupine. The experimental data indicated that Lupine is more efficient as inhibitor for the acid corrosion of non-etched aluminum. The inhibitive effect of the extract was assumed to occur via adsorption of active ingredients of the extract on the metal surface. Theoretical fitting of the data to the Kinetic-thermodynamic model were tested to clarify the nature of adsorption. The optical micrographs obtained after surface pre-treatment show that alkaline etching reveals the surface to be porous-like in structure and both the acid and extract have limited effect on the size of pores.

The eco-friendly ionic liquid 1-(2-ethoxy-2-oxoethyl) pyridazinium chloride's (EOPC) newly synthesised electro-oxidation behaviors of boron-doped diamond (BDD) and SnO2 in an alkaline media were compared using galvanostatic electrolysis. Various pyridazinium and alkaline concentrations were studied. In addition, the temperature, and density current effect of pyridazinium oxidation were investigated. The BDD showed a higher activity toward pyridazinium oxidation than the SnO2. This is mainly due to the higher characteristics and the relatively inert nature of the BDD. The bulk electrolysis tests have shown that the complete removal of COD can only be achieved using a boron-doped diamond and that SnO2 only permits a partial oxidation of pyridazinium. On the basis of the chemical oxygen demand (COD) evolution released during the treatment, a total mineralization has been proposed. Finally, electrolysis has been performed in the presence of NaCl. Based on these results, it is concluded that BDD has less poisoning effects and higher activity than SnO2 for the selective electro-oxidation of pyridazinium.

Solar cells (Gratzel cells) have been highly regarded due to their extremely efficient and low-cost process of converting sun light into electricity. In this work screen printed electrodes were fabricated by spraying organic and organometallic dyes on glass and flexible aluminum foil. These solar cells were prepared based on three dyes, namely nickel Di thiocyanato bis(triphenyl phosphine), nickel Dimethylglyoxime and Nile blue, and the performance of these dye-sensitized solar cells (DSSC) has been experimentally evaluated. The solar cells were fabricated using thin TiO2 films; these films were characterized by FTIR. The dyes were characterized using UV–Vis and typical J-V and P-V curves of the cells. The best performance was obtained for the mixture of nickel Dithiocyanatobis (triphenyl phosphine) and Nile blue with an open circuit voltage (Voc) of 976 mV using an incident irradiation of 100 mW/cm2 at 25 ºC.

The corrosion inhibition of mild steel in hydrochloric acid by polyvinyl alcohol-g-poly(acrylamide-vinyl sulfonate) has been studied by weight loss and electrochemical methods (AC impedance and DC polarisation) techniques in the temperature range of 303 – 343 K. The inhibitor was found to provide an excellent efficiency of more than 90 %. Various adsorption isotherms have been employed for fitting the obtained results to confirm the mode of adsorption of the grafted terpolymer on mild steel. Thermodynamic parameters of adsorption such as equilibrium constant, Gibbs free energy, adsorption heat and adsorption entropy were evaluated and discussed. Various parameters that determine the kinetics of mild steel dissolution such as activation energy, enthalpy and entropy were also calculated. Results obtained from various techniques were comparable and suggest that the terpolymer follows chemical adsorption mode for inhibition.

Electroless nickel composite coatings are developed by incorporating soft/hard particles into Ni-P coatings, to improve mechanical as well as tribological properties. The objective of the present work is to investigate the effect of various coating process parameters on the corrosion behavior of Ni–P–Al2O3 composite coating deposited on mild steel substrate. The electrochemical impedance spectroscopy test is used to evaluate the corrosion behavior of the heat treated composite coatings at various annealing temperatures (300 °C, 400 °C, and 500 °C). Corrosion properties, charge transfer resistance (Rct) and double layer capacitance (Cdl), are optimized using Taguchi based grey relational analysis to improve the corrosion resistance of the coating. Concentration of nickel source, concentration of reducing agent, concentration of alumina particles and annealing temperature, are considered as a main design factor for optimization of electrochemical properties. Analysis of variance (ANOVA) is used to find out the optimum combination of coating process parameters. From ANOVA result, it is found that the concentration of Al2O3 particles and annealing temperature have significant influence on the corrosion resistance of the composite coatings. Concentration of reducing agent has moderate influence on the corrosion resistance. Surface morphology of the coated surface is studied using SEM (scanning electron microscopy) and chemical composition of the coating is studied using EDX (energy dispersive X-ray analysis). The XRD (X–ray diffraction analysis) is used to understand the phase transformation behavior of the composite coatings.