INFLUENCE OF THE THERMO-MECHANICAL TREATMENT ON THE EXFOLIATION AND PITTING CORROSION OF AN AA5083-TYPE ALLOY

Exfoliation and pitting corrosion were tested on an AA5083-type alloy sheet, after applying different thermo-mechanical treatments. Hot-rolled plates were laboratory cold rolled with 16-54 % reductions, and subsequently annealed for 2 h in the temperature range from 220 degrees C to 280 degrees C. The performed tests have shown that an unacceptable exfoliation and a corrosion susceptibility were developed after the 54 % deformation and low-temperature annealing at 220 degrees C. However, no severe exfoliation was observed after the cold rolling with low deformations, independent of the applied annealing temperature. The pitting corrosion was less agressive, and the highest degree of the pitting attack was not experienced for the tested alloy. A slight tendency to pitting was detected after the high cold deformation and high-temperature annealing for the samples with recrystallized but significantly flattened grain structures.