Naslov
Electrochemical methods in the study of localized corrosion attack

Autori
Metikoš-Huković, Mirjana ; Milošev, Ingrid

Izvornik
Journal of applied electrochemistry (0021-891X) 22 (1992), 5; 448-455

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
90Cu–10Ni alloy; chloride solution; passive film breakdown

Sažetak
Electrochemical methods for determining the characteristic pitting potentials of 90Cu–10Ni alloy in slightly alkaline chloride solutions are summarized and the results of measurements carried out using potentiostatic, quasi-potentiostatic, potentiodynamic and galvanostatic techniques, complemented byex situ techniques — SEM and EDXA — are discussed. In borate buffer solution a passive state is established due to the formation of the oxide film with low ionic conductivity. However, in the presence of Cl– ions, at potentials higher than a certain critical value, breakdown of the anodic passivity occurs, caused by field-stimulated chloride entry into the passive oxide film at singular point defects. The brightening of the pits formed after oxide film breakdown was established to be due to the conversion of the passivating oxide film to one of high ion conductivity Contaminated oxide permits the passage of the metal cation into and through it, finally leaving it at the film/solution interface where pitting can proceed. During localized attack two characteristic potentials have to be distinguished: the potential of pit nucleation, E n, above which pit nucleation starts, and the breakdown potential, E b, above which the growth of nucleated pits develops. An attempt is made to compare the values ofE n andE b obtained through different methods, and to determine the factors influencing these values in each particular method.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

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