Electrochemical Corrosion Behavior of 2205 Duplex Stainless Steel Welds in Chloride Solutions

The microstructure and corrosion behavior of 2205 duplex stainless steel (DSS) welds were investigated by optical microscopy (OM), scanning electronic microscopy (SEM) and electrochemical measurements. The ferrite (delta) phase content increases slightly from the base metal (BM) zone, to the heat affected zone (HAZ) to the weld metal (WM) of the welded joint. HAZ shows a very weak sensitization that was effectively detected by the double-loop electrochemical potentiokinetic reactivation (DL-EPR) test with an H2SO4 + HCl mixed solution. In hot artificial seawater, the pitting corrosion resistance, passivation and repassivation abilities decrease gradually from BM, to WM to HAZ. Weak sensitization plays a dominant role in the pitting corrosion of HAZ even though the degree of sensitization (DOS) is very low. BM and WM do not show intergranular corrosion (IGC) susceptibility and the difference in the pitting resistance between these two zones is small. The pitting corrosion resistance of the three weld zones was discussed in detail.