Portugaliae
Electrochimica Acta

This paper aims at investigating the influence of process parameters on micro hardness of metal matrix / material particle coated steel plates. The electro deposition parameters such as current density, pH of bath, bath temperature, Al particles concentration in the bath and agitation speed were considered for this study. Nickel matrix / aluminum particle composite coatings were prepared from a Watt’s bath by electro-codeposition method. The Taguchi method was used to establish the relationship between the process parameter and response variable, micro hardness of the coated plate. L27 Taguchi orthogonal design was employed for conducting the experiments. The micro-hardness of the deposits was examined using a Vickers micro-hardness tester with the payload of 100 g for 10 sec of indentation period. Signal-to-noise ratio and analysis of variance were employed to determine the significance of the process parameter. The surface morphologies of coating and vol. % of Al particles in deposits were analyzed using optical and scanning electron microscope observations.

Corrosion behavior of aluminum in 0.1 M HCl, 0.1 M HClO4 and 0.05 M H2SO4 solutions was studied using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The results showed that the rate of corrosion of aluminum was arranged in the order: HCl > HClO4 > H2SO4. Lupine extract is an effective green inhibitor for the corrosion of aluminum in acidic solutions. The inhibition efficiency of the extract was found to increase with increasing the concentration of the extract. The obtained results showed that the lupine extract is effective in the order HClO4 > HCl > H2SO4. Theoretical fitting of the corrosion data to the Kinetic-thermodynamic model was tested to clarify the nature of adsorption.

The discoloration of the food colorant E131 (Patent Blue V) by K2S2O8 and KIO3 was investigated by spectrophotometric method. The discoloration is first order with respect to the food colorant and the oxidants. The discoloration rate constant increases with the increase in initial concentration of the oxidant and temperature; whereas discoloration decreases with the increase in concentration of E131 and chloride ion. In the presence of persulfate, Cu(II) and Fe(II) have a catalytic effect on discoloration but Ni(II) has not. The thermodynamic parameters (Ea, ∆H#, ∆S#, ∆G#) of the discoloration in the presence and absence of Cu(II) and Fe(II) are calculated.

The aim of this work was to study the effect of gadolinium content on the corrosion behavior of magnesium alloys in 1 wt.% NaCl solution at 21.5 (±0.5) °C. Four Mg-Gd alloys, namely Mg-2 wt.% Gd, Mg-5 wt.% Gd, Mg-10 wt.% Gd, and Mg-15 wt.% Gd, were studied. Weight loss measurements, potentiodynamic tests, electrochemical impedance spectroscopy, XR diffraction, and scanning electron microscopy combined with energy-dispersive X-ray spectroscopy (SEM-EDS) were performed on the four Mg-Gd samples. The results showed the influence of the Gd content on the corrosion behavior of these alloys in 1wt.% NaCl solution. The corrosion resistance of the Mg-Gd alloys was improved with the introduction of 10 wt.% Gd in Mg matrix. Thus, weight loss and electrochemical measurements revealed the better corrosion resistance for Mg-10 wt.% Gd alloy. Further addition of Gd exceeding 10 wt.% in a magnesium matrix reduces the corrosion resistance of Mg-alloy and induces an incremental increase in the corrosion rate.

The essential oil of Artemisia herba alba has been extracted and tested as an inhibitor of lead corrosion in 0.1 M Na2CO3 medium, using stationary and transient electrochemical techniques. The results obtained show that the essential oil of Artemisia reduces the corrosion rate. The effectiveness of inhibition increases with the oil concentration to reach 77 % with 2000 ppm. The effect of temperature was also studied.