Abstract: Microstructure and corrosion properties of multi-pass welded joints of 2507 hyper duplex stainless steel by multi-pass gas tungsten arc welding were studied. Two different shielding gases were used in the tungsten argon arc welding. The effect of welding pass and nitrogen addition on the microstructure and corrosion performance was discussed. The results showed that the weld center had higher austenite content. Its corrosion rate was about 0.68 times of the weld root. The weld cap showed better corrosive properties due to its obvious intragranular austenite though its austenite content was close to weld root. The weld root was the weakest region in the weld metal. The mixing zone showed the highest corrosion rate due to the existence of heat affected zone. The addition of nitrogen promoted the formation of austenite and reduced the corrosion current density by one magnitude and improved the overall corrosion performance.