Corrosion assessment of ASME qualified welding procedures for grade 2101 lean duplex stainless steel

Abstract

ASME qualified welding procedures do not guarantee suitable corrosion and passivation properties for lean duplex stainless steel welds. An evaluation of two ASME qualified welding procedures to optimize the corrosion performance of tungsten inert gas (TIG) welded grade 2101 duplex stainless steel using ER2209 weld consumable was conducted. The evolution of the microstructure was examined by optical and electron microscopy, ferrite-scope measurements, and scanning Kelvin probe force microscopy. An electrochemical mini-cell was then used to characterize the electrochemical behavior of different weld regions using the techniques such as the double loop electrochemical potentiokinetic reactivation test, standard potentiodynamic polarization tests, and cyclic potentiodynamic polarization. The fusion line was the most critical zone for localized corrosion for both welding procedures, due to the formation of Cr- and Mo-depleted zones, resulting in the highest degree of sensitization. The best performance was attributed to the weld face, due to the presence of higher Cr and Mo contents, highlighting the pitting corrosion resistance. A heat input range of 1.6 kJ/mm to 1.9 kJ/mm and low current density (WPS 1) indicated better corrosion performance of all weld regions. The electrochemical corrosion response was in all cases related to microstructural characteristics of the weld regions. The influence of weld parameters on microstructure development and corrosion performance is discussed.