Electrochemical response of AlNiLa amorphous and devitrified alloys

The electrochemical response of Al94−xNi6Lax alloys (x = 4, 5, 6, 7) after different stages of devitrification was studied in 0.05 M Na2SO4 as well as in different concentrations [0.001 M, 0.01 M and 0.1 M] NaCl solutions. Complementary crystallization studies were carried out to elucidate the composition dependent phase evolution in these alloys. It was observed that the primary crystallization did not cause any deterioration in the corrosion resistance of the alloys as compared to the amorphous alloys. In the case of Al87Ni6La7, there was actually an improvement in the passivating ability in benign media. The various primary crystalline phases in the different alloys investigated did not cause different electrochemical responses. However, the onset of secondary crystallization caused a reduction in the corrosion resistance in the NaCl media through a loss in passivating ability of all the alloys. This is due to increased galvanic activity as well as the loss of the amorphous phase.