Electrochemical methods to detect susceptibility of Ni-Cr-Mo-W alloy 22 to intergranular corrosion

Abstract

Alloy 22 (UNS N06022), a Ni-Cr-Mo-W based alloy, is a candidate material for the outer wall of nuclear waste package (NWP) containers. Even though the alloy is highly stable at low temperatures, it could undergo microstructural changes during processing such as welding and stress relieving. Formation of topologically close-packed (TCP) phases such as , P, , etc. and Cr-rich carbides could make the material susceptible to localized corrosion. Hence, it is important to correlate the microstructural changes with the corrosion resistance of the alloy by nondestructive and rapid electrochemical tests. In this investigation, different electrochemical test solutions were used to quantify the microstructural changes associated with aging and welding of the wrought alloy 22. The results of double-loop (DL) electrochemical potentiodynamic reactivation (EPR) tests in 1 M H 2 SO 4 ϩ 0.5 M NaCl ϩ 0.01 M KSCN solution indicated Cr depletion during initial stages of aging of wrought alloy 22. Results of EPR tests in 2 M HCl ϩ 0.01 M KSCN solution at 60 °C correlated well with the Mo depletion that occurred near TCP phases formed during aging of both weld and wrought alloy 22 materials. The EPR test results were compared with standard chemical weight loss measurements specified by ASTM standard G-28 methods A and B.

Effect of The Degree of Cold Work and Sensitization Time on Intergranular Corrosion Behavior in Austenitic Stainless Steel

“…2,3). The obtained results are consistent with the general view that cold work before sensitization, reduces the intensity of intergranular corrosion [13][14][15]. This is due to the deformation of the structure (twins, slip bands, stacking errors, grain refinement) ( Fig.…”

Characterization of surface composition on Alloy 22 in neutral chloride solutions

“…These alloys are widely used in a range of industrial applications, and Alloy 22 was recently considered as the corrosion barrier on packages for the permanent disposal of nuclear wastes . This last potential application stimulated many studies on this alloy and, to a lesser degree, other Ni‐Cr‐Mo alloys, on processes such as intergranular corrosion, localized corrosion with an emphasis on crevice corrosion, stress corrosion cracking, and general passive corrosion …”

Mechanical Properties and Corrosion Resistance of a Novel Ni‐Cr‐Mo Alloy

“…[4] An extensive amount of research on Ni-Cr-Mo alloys has been reported. [1,2,[4][5][6][7][8][9][10][11][12][13][14][15][16][17] One of the typical alloys is named Haynes 242 alloy with a nominal composition of Ni-8Cr-25Mo (wt.%); this material exhibits excellent high-temperature strength and ductility, low thermal expansion characteristics, good oxidation resistance and excellent fabricability. [1,2,5] The chemical composition and heat treatment of Ni-Cr-Mo alloys have also been investigated.…”