Portugaliae
Electrochimica Acta

The electrochemical properties of rhodium(III) 1-3 and iridium(III) 4-6 complexes containing bis(pyrazolyl)alkane ligands [MCp*Cl(R2C(3,5-R’2pz)2)]X (M = Rh (1) or Ir (4), R = R’ = H, X = Cl; M = Rh (2) or Ir (5), R = H, R’ = Me, X = Cl; M = Rh (3) or Ir (6), R = Me, R’ = H, X = OTf; pz = pyrazolyl; Cp* =h5-C5Me5) were investigated by cyclic voltammetry and controlled potential electrolysis. They exhibit two sequential irreversible reductions assigned to the M(III) -> M(II) and M(II) ->M(I) reductions, which are dependent on the methylation of the bis(pyrazolyl)alkane ligands.

The inhibition performance of a non-oxidising surfactant, namely cetyl trimethyl ammonium bromide (CTAB), and its co-adsorption behaviour with zinc ion on carbon steel in well water was studied by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), weight loss, as well as atomic force microscopy (AFM) and scanning electron microscopy. Results indicated that the formulation acted as an anodic inhibitor. Adsorption of the used inhibitor led to a reduction in the double layer capacitance and an increase in the charge transfer resistance. A synergistic effect was also observed for the studied inhibitor with Zn(II) in weight loss measurements and electrochemical studies.

The inhibition effect of Mentha pulegium extract (MPE) on the acid corrosion of carbon steel in 1 M HCl solution was investigated using weight loss, potentiodynamic polarisation, and electrochemical impedance spectroscopy. The results show that the Mentha pulegium extract is a good inhibitor, and that the inhibition efficiency depends on the concentration of the plant extract. Efficiency is higher than 88 % for 33% Mentha pulegium extract. Polarization measurements also show that Mentha pulegium extract is a good mixed inhibitor. The remarkable inhibition efficiency of MPE was discussed in terms of blocking of the electrode surface by adsorption of inhibitor molecules through active centres. Mentha pulegium extract is adsorbed on the carbon steel surface according to the Temkin adsorption model. The effect of temperature on the corrosion behaviour of carbon steel in 1 M HCl with addition of 33% MPE was studied in the temperature range 308-338 K. SEM also confirmed the adsorption of MPE on carbon steel surface.

In this study polypyrrole (PPy) bilayers films were electrodeposited onto SAE 4140 steel. The inner layer was electropolymerized in the presence of molibdate and nitrate and the outer layer in a solution containing sodium bis (2-ethylhexyl) sulfosuccinate (AOT). The electrosynthesis was done under potentiostatic conditions. The corrosion protection properties of the films were examined in sodium chloride solution by open circuit measurements, linear polarization and electrochemical impedance spectroscopy (EIS). The bilayer coatings present an improved anticorrosive performance with respect to single PPy films.

Electroreduction properties of salicylic (SA) and acetylsalicylic (ASA) acids were investigated at platinum electrode using the voltammetry method. Cyclic voltammograms (CV) of the tested compounds were used in determining half-wave potential (E1/2) - the parameter describing the anti-reductive properties. The content of active substances (SA and ASA) in the selected pharmaceuticals (salicylic alcohol, Bayer aspirin, etopirin and polopirin) was examined with the application of electrochemical and spectrophotometric methods.