Alloy 33 (UNS R20033), a new chromium-based corrosion resistant austenitic material with nominally (wt. %)33 Cr, 32 Fe, 31 Ni, 1.6 Mo, 0.6 Cu, 0.4 N has been introduced to the market in 1995. This paper provides new data on this alloy with respect to mechanical properties, formability, weldability, sensitization characteristics and corrosion behavior. Mechanical properties of weldments including ductility have been established, and match well with those of wrought plate material, without any degradation of ISO V-notch impact toughness in the heat affected zone. When aged up to 8 hours between 600°C and 1000°C the alloy is not sensitized when tested in boiling azeotropic nitric acid (Huey test). Under field test conditions alloy 33 shows excellent resistance to corrosion in flowing 96 -98.5 % H2SO4 at 135°C - 140°C and flowing 99.1% H2SO4 at 150°C. Alloy 33 has also been tested with some success in 96 % H2SO4 with nitrosyl additions at 240°C. In nitric acid alloy 33 is corrosion resistant up to 85% HNO3 and 75°C or even more. Alloy 33 is also corrosion resistant in 1 mol. HCI at 40°C and in
NaOH/NaOCl-solutions. In artificial seawater the pitting potential remains unchanged up to 75°C and is still well above the seawater’s redox potential at 95 °C. Alloy 33 can be easily manufactured into all product forms required. The new data provided support the multipurpose character of alloy 33 to cope successfully with many requirements of the Chemical Process Industry, the Oil and Gas Industry and the Refinery Industry.
Keywords: Alloy 33, UNS R20033, sulfiric acid, nitric acid, local corrosion, alkaline solutions, sensitization, welding