Effect of welding on the microstructure and electrochemical corrosion of Al-Zn-Mg-Fe alloys

The effect of gas tungsten are welding on the microstructure and electroche mical corrosion of Al-Zn-Mg-Fe alloys submitted to different heat treatment s (as fabricated, annealed and aged) has been studied using optical microsc opy, SEM, TEM, EDX, cyclic voltammetry and corrosion potential measurements in chloride solutions. The electrochemical techniques were very sensitive to the change in the phase compositions produced by welding. Welding caused a decrease in the mean grain size, in the hardness and in the corrosion re sistance of the age-hardened alloys. The structure of the latter became str ongly altered by welding to lead to phase compositions very close to those of the cold rolled and annealed specimens. (C) 2000 Elsevier Science Ltd. A ll rights reserved.