抄録
The general corrosion resistance of the quaternary aluminum-lithium alloy ‘Navalite’ (Al–2Li–1.2Cu–3Mg) in the maximum strength, peak-aged condition was evaluated in environments spanning an entire range of aggressiveness. The corrosion rate was established through loss of mass measurements obtained from coupons. Total immersion test results indicate that loss of mass occurred in both acidic and basic solutions. Long-term corrosion rate was observed to decrease with time of immersion in the solution. The pH of the solutions changed during the period of testing. Analytical study of the surfaces of the samples by scanning electron microscopy and transmission electron microscopy revealed that the alloy samples begin to corrode rapidly during the initial period of immersion in the solution followed by a period of uniform corrosion in which pitting dominates. In the highly hostile/aggressive environments there occurred enhanced corrosion along the grain boundaries. In the less hostile environments and in the neutral solution pitting corrosion dominated. Pitting was observed to occur at the second-phase particles dispersed in the matrix, and at the grain boundary precipitate particles. The number, density and size of pits increased with immersion time. The results obtained from the total immersion tests suggest the operation of several concurrent and competing processes involving alloy composition, intrinsic microstructural features, and chemistry of the aqueous solution.
