Corrosion rate of the X2CrNiMoN22-5-3 duplex stainless steel annealed at 500 cc

The X2CrNiMoN22-5-3 duplex stainless steel has an austenitic-ferritic microstructure with an average fraction of each phase of approximately 50%. At the duplex stainless steel the nitrogen serves to significantly improve the corrosion resistance of the alloy also in the welded condition. These steels present the excellent corrosion resistance of austenite steel, and the high mechanical behaviour of ferrite steel. However, the performance presented by duplex stainless steels can be drastically reduced by undesirable phases, such as sigma phase, chi phase, secondary austenite and a lot of chromium-rich and carbides precipitates. In this case an upper temperature limit of 300°C has been placed in the use of X2CrNiMoN22-5-3 steel in the industry mainly due to 475°C embrittlement. The purpose of this work was to ascertain how 60 min isothermal heat treatments at 500°C and corrosion time influence on the relative mass loss, profile roughness parameters and endothermal process by dynamic scanning calorimetry curves of heating measurement from 400 to 600°C of X2CrNiMoN22-5-3 duplex stainless steel. The influence of boiling nitric acid on the steel corrosion resistance was investigated using weight loss and profile roughness parameters.