09426 Assesment of Nickel-Based Alloy Passive Film Stability Through Thermodynamic Modeling

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Product Number: 51300-09426-SG

ISBN: 09426 2009 CP

Author: Roberto Pabalan, Pavan K. Shukla and Lietai Yang

Publication Date: 2009

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Nickel-based alloys such as Alloy 600, Alloy 22, and C-276 exhibit better corrosion resistance compared to iron-based alloys such as stainless steel. For this reason, nickel-based alloys are preferred in nuclear systems. The corrosion resistance of nickel-based alloys can be attributed to the stability of the protective passive oxide film that forms on the metal surface. The passive film acts as a barrier between the metal surface and corrosive salt solutions present in the environment. However, the corrosion resistance of nickel-based alloys can be compromised in aggressive environments where the passive film constituents dissolve. In this paper, it is hypothesized that the dissolution of the passive film in a given environment would correlate with a diminished corrosion resistance of nickelbased alloys. This hypothesis is tested by using thermodynamic modeling to evaluate the thermodynamic stability of the passive films of various nickel-based alloys in various salt solutions. A chemical thermodynamic software is used to determine the potential passive film constituents and, subsequently, to calculate the solubility of those constituents in different chemical environments. The calculated solubilities are compared with published experimental data. The results of this study show that the increase in the solubility of passive film constituents correlates well with the decrease in corrosion resistance of nickel-based alloys.

Keywords: Alloy 600, Alloy 200, C-276, passive film, thermodynamic analysis, solubility