The influence of fluoride on the anodic dissolution kinetics of titanium was studied by several electrochemical techniques at steady-state open-circuit potentials in 1.0 M HClO 4 containing fluoride with various concentrations ranging from 0 to 0.1 M. The promoting effect of fluoride ͑especially when ͓F − ͔ Ͼ 1 ϫ 10 −3 M͒ on the anodic dissolution behavior of titanium was characterized and discussed by taking into account the changes in the estimated electrochemical and kinetic parameters. The faradaic impedance for the anodic dissolution of titanium was analyzed both by fitting based on an equivalent electrical circuit model and by theoretical derivation based on a two-step mechanism involving one adsorbed intermediate species. By correlating the faradaic impedance expression derived from the dissolution mechanism with that deduced from the equivalent electrical circuit model, some important kinetic parameters ͑such as the apparent rate constants K 1 and K 2 and the surface coverage ss ͒ could be estimated from the equivalent circuit elemental parameters ͑such as R ct , R a , and C a ͒. The charge-transfer reaction was the rate-determining step at lower fluoride concentrations of ͓F − ͔ Յ 1 ϫ 10 −3 M, leading to a high surface coverage of ss Ϸ 1, while the chemical dissolution reaction is the rate-determining step at higher fluoride concentrations of ͓F − ͔ Ͼ 1 ϫ 10 −3 M, leading to a decreased surface coverage of ss Ͻ 0.5.Titanium ͑and its alloys͒ is one of the most important metal materials widely used in engineering and technological applications. 1 Titanium-based materials possess excellent corrosion resistance in various electrolyte solutions due to the easy formation of a highly protective oxide film at the titanium ͑and its alloys͒ surface. But some aggressive inorganic anions such as F − and Cl − existing in aqueous environments can attack the passivity of titanium and its alloys. [2][3][4] The effects of solution pH and fluoride concentration on the anticorrosion properties of the surface passive TiO 2 films formed by anodic oxidation of titanium at different passivation potentials were widely investigated by many researchers using various electrochemical and surface analytical techniques. 3,5-10 The active-passive transition kinetics of titanium in electrolyte solutions without 11-15 and with fluoride 9,16 was also studied using various electrochemical methods. However, very few studies were reported on the dissolution mechanism and kinetics of titanium in fluoride-containing solutions at open-circuit potentials ͑OCPs͒. 16 Recently, we investigated the influence of fluoride concentration and the film formation potential on the bulk and surface properties of anodic oxide films ͑as well as their breakdown͒ formed on titanium in fluoride-containing perchloric solutions. 3 The passivity of titanium would be destroyed by the chemical dissolution of the oxide if the fluoride concentration was higher than 1 ϫ 10 −3 M. 3 This work investigates the effect of fluoride on the anodic dissolution kinetics of metal ...

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The electrocatalytic properties of a SiC particle-modified glassy carbon electrode (MGC) for adrenaline oxidation were studied by cyclic voltammetry, double-potential step chronoculometry and electrochemical impedance spectroscopy in a pH 7.4 physiological Kres?Ringer phosphate buffer (KRPB) solution. It was shown that modification of the electrode with SiC particles has a marked electrocatalytic effect on the electrochemical reaction of adrenaline, i.e., the activity and the reversibility of the MGC electrode were significantly improved compared to an unmodified electrode. This was attributed to the adsorption effect of the electroactive adrenaline molecules on the MGC electrode surface. .