Portugaliae
Electrochimica Acta

Silver chloride modified carbon paste electrode was prepared as a new electrode and used to electrocatalytic oxidation of ethanol. For the first time, the catalytic oxidation of ethanol was demonstrated by cyclic voltammetry, chronoamperometry and amperometry methods at the surface of this modified carbon paste electrode. Compared to silver chloride modified carbon paste electrode, silver bromide modified carbon paste electrode and bare silver electrode catalysts, silver chloride modified carbon paste electrode exhibited markedly superior catalytic activity for the electrocatalytic oxidation of ethanol. It can be seen that the electrocatalytic efficiency of silver chloride modified carbon paste electrode is higher than the silver bromide modified carbon paste and bare silver electrodes. The catalytic oxidation peak current was linearly dependent on the ethanol concentration. The j0 for silver chloride modified carbon paste and silver bromide modified carbon paste electrodes are 11.2 and 5.4 folds respectively higher than that of the bare silver electrode. For silver chloride modified carbon paste electrode, the charge transfer coefficient (α), the number of electrons involved in the rate determining step (nα) and exchange current density (j0) were calculated as 0.46, 1 and 5.05×E–7 respectively. The modified electrode possesses high selectivity, good reproducibility and well stability.

A novel self modification of grafted polymer working electrode with carbon nanotubes was success for fabrication from grafting polymer via gamma irradiation and ferrous ammonium sulfate (FAS) as a catalyst. The electrochemical properties of the self modified grafted polymer with CNT (GPESMCNT) improved performance the working electrode at higher conducting surface was done through using in cyclic voltammetry (CV). The GPESMCNT was characterized by surface analytical methods including AFM and SEM. The characterization of electrocnductivity properties of GPESMCNT was studied in 1M of KCl with different concentration of K3[Fe(CN)6], at different scan rates, temperature, and different concentrations using CV technique. The new GPESMCNT improved performance the working electrode in CV at different techniques such as rotating disc electrode (RDE). also, the nanomaterials in the chain of grafted polymer was enhanced the redox current peaks of Fe(II)/Fe(III) multi times than at commercial working electrodes such as GCE, Pt-electrode, Au-electrode, etc.

Electro polishing is defined as anodic corrosion. The issue of the effects of corrosion on structural integrity of metal surfaces has been a question of concern for some time. The uses of chemical corrosion inhibitors are common in production and processing operations. Nevertheless, the challenge is to develop a new class of corrosion inhibitors to protect the materials, due to the economic importance of copper there are several researches deals with acceleration and inhibition of this process. In this paper the electropolishing process inhibited with different ratio by addition of some organic alcohols (methanol, ethanol,propanol, and isopropanol) by addition with concentration (2, 5, 10, 15, 20, 25 and 30 %) .The results reveal that these organic alcohols have a strongest inhibitive effect ranging from8. 7 – 53.8 % and the thermodynamic parameters were present.

The assessment of Psidium guajava leaf extract as corrosion inhibitor for double thermally-aged Al-Si-Mg (SSM-HPDC) alloy in 3.5%wt NaCl solution using the gravimetric and potentiodynamic polarization techniques was investigated. The gravimetric test was carried out at different inhibitor concentration, time and temperature ranges of 0.1-0.5%v/v, 1-5 hrs and 30-70oC. The results revealed that Psidium guajava leaf extract in 3.5%wt NaCl solution-aluminium environment decreased the corrosion rate at various concentrations considered. Inhibition efficiency (IE) of 72.1% at 0.5% v/v Psidium guajava leaf extract addition using the gravimetric method was demonstrated in 3.5%wt NaCl solution. The IE from the potentiodynamic polarization method was significantly enhanced as high as 98.89%/0.5%v/v. The additions of Psidium guajava leaf extract as corrosion inhibitor in the solution indicate higher potential value, IE and polarization resistance with decrease in current density. The methods for assessment of the alloy were in agreement and mixed-type corrosion exist which obeyed the Langmuir adsorption isotherms. The optical microscopy (OPM) revealed that the microstructure of the double thermally-aged sample has finer grains and enhanced grain boundaries compared to the untreated sample. The scanning electron microscope (SEM) surface morphology of as-corroded uninhibited condition showed severe damage and pit formation than as-corroded inhibited.

Cefuroxime axetil (CA) a prodrug was tested as corrosion inhibitor for aluminum in hydrochloric acid solution using thermometric, gasometric weight loss and scanning electron microscope (SEM) techniques. Results obtained showed that this compound has a good inhibiting properties for aluminum corrosion in acidic medium, with inhibition efficiencies values reaching 89.87 % at 0.5 g / L . It was also found out that the results from weight loss method are highly consistent with those obtained by hydrogen evolution method and gasometric method; and all indicate that inhibitor efficiency increases with increasing inhibitor concentration. Cefuroxime axetil inhibited the corrosion of aluminum in solutions of HCl through the mechanism of physiosorption as confirmed by values of activation energy and free energy of adsorption. The adsorption of the inhibitor was also found to be spontaneous, exothermic and best fitted the Langmuir adsorption model. SEM analysis confirmed the existence of an absorbed protective film on the aluminum surface.