Factors which can have a detrimental effect on the corrosion performance of welded duplex stainless steel are discussed together with applicable countermeasures. The main focus is on pitting corrosion resistance on the root side and how this can be improved by adequate backing gas protection and post-weld cleaning (acid pickling). The positive effect of nitrogen in the shielding and backing gas on the austenite formation and pitting corrosion resistance of welds in the lean duplex stainless steel LDX 2101® (EN 1.4162, UNS S32101) is demonstrated. On the rootside, welding with nitrogen-based backing gas significantly increased the critical pitting resistance compared to welding with argon. The highest values, close to that of the base metal, were obtained using 90 % N2 + 10 % H2 as backing gas. The results are compared to the values reported in the literature and the differences between the ASTM G150 and ASTM G48 corrosion test methods highlighted.