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Modelling the electrochemical crack size effect on stress corrosion crack growth rate

Turnbull, A; Wright, L (2017) Modelling the electrochemical crack size effect on stress corrosion crack growth rate. Corrosion Science, 126. pp. 69-77.

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Stress corrosion and corrosion fatigue crack growth rates in a 12Cr martensitic stainless steel in low conductivity solutions were observed to be crack size dependent. A conceptual framework was developed to rationalise this based on the extent of electrochemical coupling between the crack tip and the external surface remote from the crack, which was projected to be strongly affected by solution conductivity. To provide a theoretical foundation for this concept a new model has been developed to predict the crack-tip potential and local chemistry as a function of crack size and bulk solution conductivity. The model focuses on stress corrosion cracks only and incorporates mass transport (diffusion and ion migration) and chemical and electrochemical reactions in the crack, with the potential drop in the bulk solution outside the crack calculated from the solution to Laplace's equation. In the context of the bulk solution the implications for crack-tip electrochemistry of full immersion vs a thin liquid layer associated with a condensing environment was explored. The model predictions provide support for the concept of a solution conductivity dependent crack size effect on crack growth rates.

Item Type: Article
Keywords: stainless steel; steam turbine; modelling; stress corrosion cracking
Subjects: Advanced Materials > Corrosion
Divisions: Engineering, Materials & Electrical Science
Identification number/DOI: 10.1016/j.corsci.2017.06.016
Last Modified: 01 Mar 2018 11:19
URI: http://eprintspublications.npl.co.uk/id/eprint/7748

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