Electrochemical characterization of oxide film formed at high temperature on Alloy 690

摘要

High temperature passivation studies on Alloy 690 were carried out in lithiated water at 250 ℃, 275 ℃ and 300 ℃ for 72 h. The passive films were characterized by glow discharge-quadrupole mass spectroscopy (GD-QMS) for compositional variation across the depth and micro laser Raman spectroscopy for oxide composition on the surface. The defect density in the oxide films was established from the Mott-Schottky analysis using electrochemical impedance spectroscopy. Electrochemical experiments at room temperature in chloride medium revealed best passivity behaviour by the oxide film formed at 300 ℃ for 72 h. The electrochemical studies were correlated to the chromium (and oxygen) content of the oxide films. Autoclaving at 300 ℃ resulted in the best passive film formation on Alloy 690 in lithiated water.