ELECTROCHEMICAL CHARACTERISTICS OF AL-AL3 NI EUTECTIC ALLOY ELECTRODES

The electrochemical characteristics of Al-Al3Ni eutectic alloys were i nvestigated by polarization tests and potentiostatic dissolution tests . EDAX analysis of various phases in the alloys and scanning electron microscopic observation of the surface of the alloys corroded in a dil ute HClO4 solution were also performed. The results obtained are summa rized as follows: (1) The anodic dissolution rates of Al-Al3Ni eutecti c alloys in a dilute HClO4 solution increase with increasing HClO4 con centration and solution temperature. However, the rates are decreased in the order of Al-5.65 mass%Ni alloy > Al-29.8 mass%Ni alloy > Al-42. 57 mass%Ni alloy. The anodic dissolution rates increase with increasin g surface area rations of eutectic stracture in the alloys. (2) The ap parent activation energies of anodic dissolution are 30.6 kJ/mol for t he Al-5.65 mass%Ni alloy, 33.4 kJ/mol for the Al-29.8 mass%Ni alloy an d 44.6 kJ/mol for the Al-42.57 mass%Ni alloy, respectively. (3) The ma in anodic dissolution reaction of all the alloys in the dilute HClO4 s olution is the selective dissolution of the Al(alpha) phase from the A l(alpha)+Al3Ni(beta) eutectic structure. However, on the Al-42.57 mass %Ni alloy, the dissolution of Al from Al3Ni(beta) occurs as a side rea ction.