Avaliação da resistência à corrosão da liga 2024-T351 soldada por FSW Friction Stir Welding
Abstract
The corrosion resistance of aluminum alloy can be impaired due to
intermetallic precipitation during thermal treatment to improve mechanical
properties. This work investigates the corrosion resistance of aluminum alloy
2024-T351 and the joint welded by FSW. Microstructural analysis and
microhardness tests were made. Intergranular corrosion tests according to
ASTM G110-97, exfoliation corrosion tests according to ASTM G 34-01 and
stress corrosion cracking in 3.5% NaCl according to ASTM G 129-00, were
carried out. Anodic behavior was evaluated by potentiodynamic polarization
measurements in 3.5% NaCl solution. It was not detected intermetallic
precipitates by electron and optical microscopy. It was also detected that the
joint was more severe attacked than the base metal by intergranular corrosion
and exfoliation tests. The welded joint was susceptible to stress corrosion
cracking in tests carried out with low nominal strain rate of 10-7 s-1. Base metal
and the joint in tests carried out in air and in 3.5% NaCl at strain rate of 10-6 s-1
showed ductile behavior, while the joint with strain rate of 10-7 s-1 showed fragile
behavior. The polarization test in chloride medium of aluminum alloys didn t
show passive breakdown what make difficult to determinate the pitting potential.
Polarization curves indicated that the welded joint had lower current density and
higher potential than the base metal. In lower potentials pitting was formed
majoritary at grain boundaries