EFFECT OF GERMANIUM ADDITIONS ON THE CORROSION BEHAVIOR OF AN AILI ALLOY

Three compositions were used in the experiments: (1) 99. 98 Al, (2)-2. 5 Li, and (3) Al-1. 9 Li-0. 2 Ge. The two alloys were solutionized and quenched, then age hardened to 80% of peak strength for both the underaged and overaged conditions. Immersion test results indicate few differences in the samples. The severity of pitting corrosion does not increase significantly beyond 30 days of immersion. The metals begin to corrode uniformly after an initial period during which pitting corrosion dominates. The alloys also undergo enhanced corrosion at grain boundaries in the 75-and 120-day samples. The presence of lithium does not significantly affect the electrochemical behavior of aluminum. The underaged ternary alloy is more stable in terms of breakdown, repassivation, and current density. The results of immersion and electrochemical tests are discussed in terms of microstructural parameters.