Some studies on pitting corrosion of AA2219 alloy and its TIG welds

The study pertains to the pitting corrosion resistance of AA2219 wrought alloy and its weld. Continuous current tungsten inert gas (CCTIG) welding was used to prepare autogenous welds of the alloy in artificially age-hardened condition (T6). Post weld heat treatment (PWHT) of samples were done at 463 K for 18 h. The surface modification of test samples was done using AC Polarization, to remove copper rich precipitate. Pitting resistance of base metal and welds with and without copper rich phase removal was evaluated by Potentiodynamic Polarization tests, Scanning Electron microscopy and Transmission Electron Microscopy. Significant improvement in pining corrosion resistance of the base metal (T6) has been observed after the removal of copper and the parameters have been optimized for the effective removal of copper-rich phase from the surface. Pitting resistance of PWHT specimens was inferior to that of as welded counter pan. Surface pre-treatment of copper rich phase removal resulted in improvement of pitting resistance and nearly same pitting potential in all the regions of weldment.