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The growth mechanism and electrochemical properties of an oxide film on AISI 304 grade stainless steel were studied in 0.01 and 0.1 mol L−1 fluoride solutions with different pH values (4.5, 5.5, 6.5) by means of electrochemical techniques. The anodic growth and stability of the oxide film on the stainless steel were characterized using cyclic voltammetry. Potentiodynamic analysis suggests that the oxide film growth occurs according to the high-field mechanism. Electric field strength, high-field growth exponential law constants, ionic conductivity through the film and half jump distance were determined. The electrochemical properties of the oxide film, formed spontaneously at the open circuit potential, were studied using electrochemical impedance spectroscopy. The results showed that the fluoride concentration has more considerable influence on the dissolution rate and the resistance of the oxide film than the pH.

The effect of the addition of small quantities of gallium to high-purity aluminium (99.999 wt%) on its electrochemical behaviour at high cathodic potentials (up to -2.0 V versus SCE), has been investigated using the potentiostatic pulse method. After cathodic polarization, anodic current was traced versus time to determine the quantity of charge necessary for oxidation of substances formed. Anodic current responses to the return to the E OCP were also recorded in the period of 1 s. Time responses of the cathodic and anodic currents were analyzed. The cyclic voltammetry method was used to determine the hydration potential. The range of low and high cathodic potentials (LCP, HCP) was defined for all the samples. It has been established that the oxide film retains its properties in the LCP range, while in the HCP range cathodic breakdown and hydration of the oxide take place. Electrochemical methods complemented the SEM and EDAX analysis before and after the cathode pulse of -1.9 V versus SCE.

The influence of the addition of small quantities gallium to highpurity aluminium on its electrochemical behaviour at high cathodic potentials (up to -2.0 V vs. SCE) was investigated using the potentiostatic pulse method. After cathodic polarization, anodic current was traced vs. time in order to determine the quantity of charge necessary for oxidation of substances formed. Anodic current responses to the return to the E OCP were also recorded in the period of 1 s. Time responses of the cathodic and anodic current were analyzed. The range of low and high cathodic potentials (LCP, HCP) was defined for all the samples. It has been established that the oxide film retains its properties in the LCP range, while in the HCP range cathodic breakdown and hydration of the oxide take place. Electrochemical methods complemented by SEM and EDAX analysis before and after the cathode pulse of -1.9 V vs. SCE.

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