Exfoliation and Pitting Corrosion Susceptibility in a Modified 5083 Type Aluminium Alloy Akram Halap 1 , Miljana Popović 1 , Veselin Vaščić 2 , Tamara Radetić 1 , Endre Romhanji 1 1 Dept. Metall. Eng., Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, 11120 Belgrade, Serbia 2 Freelance Consultant e-mail: akrmhlp68@yahoo.com , endre@tmf.bg.ac.rs Abstract Exfoliation and pitting corrosion were tested in a 5083 type alloy sheet (modified with an addition of 0.5 wt.% Zn), after applying different thermo-mechanical treatments. Hot rolled 5083 plates were laboratory cold rolled to 15% - 54%, and subsequently annealed at 220C and 280C. The performed tests have shown that exfoliation corrosion developed after > 50% cold rolling deformation and low temperature annealing at 220C and 230C. The pitting corrosion was less agressive and appeared to be active after higher cold rolling deformations (40% - 50%) and higher annealing temperatures (260C and 280C). Keywords: 5083 Aluminium Alloy, Thermo-mechanical Treatment, Exfoliation, Pitting Introduction Al-Mg alloys found a wide range of applications, especially in the constructions of transportation means due to the attractive strength to weight ratio, good weldability and formability as well as a high corrosion resistance [1-8]. However, Al-Mg alloys with more than 3% Mg, due to the limited room temperature solubility of Mg in Al matrix (1.9 wt.% Mg), can be sensitized and become susceptible to intergranular corrosion (IGC) [9-13]. One of the manifestations of IGC is a specific lamellar type of corrosion, with a blister surface appearance, known as exfoliation. It is a form of IGC that occurs on the surface of wrought aluminium alloys [14-16], with a highly flattened grain structure. Another, probably the most common corrosion type, also associated with a specific surface appearance, is a pitting corrosion. It is a form of extremely localized corrosion that leads to the creation of small holes or pits in the structure, usually covered by the corrosion products. The objective of this work is a consideration of exfoliation and pitting corrosion appearance in a 5083 type alloy sheet, modified with Zn addition, after applying different thermo-mechanical treatments. Experimental Material. The as received material was hot rolled 7.4 mm thick 5083 type alloy plate, supplied by Impol-Seval Aluminium Rolling Mill. The chemical composition of the tested alloy is given in Table 1. Commercial 5083 type alloy was modified with an addition of 0.5 wt.% Zn, which is approximately as double as the Zn level limit of 0.25 wt. % defined by the ASTM standard for 5083 type alloy (B 928/B 928M – 04a).