Abstract
The purpose of this study is to explain the electrochemical behavior of aluminum-lithuim (Al-Li) alloys, to relate the potentiodynamic behavior to stress-corrosion behavior, and to propose a possible means of accelerated stress-corrosion testing. Potentiodynamic polarization tests in 3.5% NaCl aqueous solution of varying oxygen content were conducted for five Al-Li alloys having ingot or powder-metallurgical alloyed product forms. Oxygen content of the sodium chloride electrolyte was demonstrated to be a key factor in determining the electrochemical behavior, and the current-voltage characteristics are defined by this parameter. In general, the potentiodynamic behavior of Al-Li alloys was found to be quite insensitive to variation in compositional content and heat treatment, factors which profoundly affect the stress-corrosion behavior. Large variations in the character of pitting and associated intergranular attack were observed. However, surface redox reactions involving oxygen and hydrogen dominate the current voltage characteristics, and the localized corrosion was not revealed therein. Alternate-immersion exposure prior to potentiodynamic polarization may offer a means of assessing susceptibility to localized corrosion.