CURRENTLESS BEHAVIOR OF ALUMINUM ALLOYS CONTAINING DIFFERENT VANADIUM PERCENT AS MINOR ALLOYING ELEMENT IN SULPHURIC ACID SOLUTIONS

The effect of vanadium (percentage) as minor alloying element on the open-circuit behavior of Al alloysin H2SO4 solutions were studied under different environmental conditions, e.g. acid concentration,solution state and temperature, using potential, EIS measurements and SEM for morphological investigation. For comparison the same measurements were done for pure Al. The results indicate that the presence of V affect the behavior of Al alloys; especially, during the first immersion period as obvious from open-circuit measurement, via transition-states depending on V%. The first transition state is associated with Emin for alloys containing 0.78%V and the second with Emax for higher V% content of the alloy. The values of Emin and Emax are greatly affected by solution state and temperature as well as acid concentration. Such transition states were discussed on the basis of anodic, cathodic and dissolutionreactions likely to occur during measurements. Generally, the steady state potential for Al-V alloys Ess isless negative than that for pure Al. EIS measurements and SEM inspection indicate that the oxide formedon tested electrodes are nonhomogeneous and of mixed oxides type as compared for one oxide type incase of pure Al. Also, the formed barrier film is of duplex nature, an inner layer consists of anhydrousoxide and an outer hydrated oxide layer responsible for dissolution or corrosion under the different environmental factors.