In the present study, the corrosion behaviour of trimetallic joint obtained from gas tungsten arc welding process in conventional mode and in pulsed mode has been investigated. The candidate materials for these studies are aeronautical steel AISI 4340 and austenitic stainless steel AISI 304L joined with filler ER309L. Potentiodynamic polarization studies were carried out on this trimetallic joints in synthetic sea water environment in order to understand the corrosion behaviour and corrosion rate. This investigation showed that the trimetallic joints obtained from pulsed current mode exhibited better corrosion resistance due to the presence of finer grains. © 2014, Sphinx Knowledge House. All rights reserved.