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Laycock N.J.,Quest Integrity Group | Krause D.P.,Industrial Research Ltd. | Ghahari S.M.,University of Birmingham | Davenport A.J.,University of Birmingham | And 3 more authors.
ECS Transactions | Year: 2012

In-situ synchrotron radiography has been used to observe propagating 2D pits in a thin foil of 304 stainless steel sandwiched between glass slides. Key kinetic parameters have been extracted from these radiographs such that they can be used as input parameters for numerical simulations of pitting corrosion. Simulation results are presented for pits growing under potentiostatic control, with a focus on propagation stability in the concentrated (> 1M) chloride solutions that cause atmospheric pitting corrosion of 304 stainless steel. ©The Electrochemical Society. Source


Ghahari S.M.,University of Birmingham | Krouse D.P.,Industrial Research Ltd. | Laycock N.J.,Quest Integrity Group | Rayment T.,University of Birmingham | And 9 more authors.
Corrosion Engineering Science and Technology | Year: 2011

In situ synchrotron radiography has been used to observe the evolution of two-dimensional pits growing in stainless steel foils under electrochemical control in chloride solutions. A method for extracting the key kinetic parameters from radiographs is under development to provide data for validating and calibrating a two-dimensional finite element model previously developed by Laycock and White. The local current density along the boundary of a pit is directly measured from the radiographs. Then, the local metal ion concentration and potential drop inside the pit cavity are backcalculated using transport equations and the requirement to maintain charge neutrality, giving the relationship between current density, solution composition and interfacial potential. Preliminary comparisons show qualitative correlation between the model and extracted data; quantitative comparison is under way. © 2011 Institute of Materials, Minerals and Mining. Source


Ghahari S.M.,University of Birmingham | Davenport A.J.,University of Birmingham | Rayment T.,University of Birmingham | Rayment T.,Diamond Light Source | And 8 more authors.
Corrosion Science | Year: 2011

Pitting corrosion of stainless steel has been investigated with high-resolution in situ X-ray microtomography. The growth of pits at the tip of stainless steel pins has been observed with 3D microtomography under different conditions of applied current and cell potential. The results demonstrate how pits evolve in stainless steel, forming a characteristic " lacy" cover of perforated metal. In addition, it is shown how the shape of pits becomes modified by MnS inclusions. © 2011 Elsevier Ltd. Source


Ghahari S.M.,University of Birmingham | Krouse D.P.,Industrial Research Ltd. | Laycock N.J.,Quest Integrity Group | Rayment T.,University of Birmingham | And 9 more authors.
Energy Materials: Materials Science and Engineering for Energy Systems | Year: 2012

In situ synchrotron radiography has been used to observe the evolution of two-dimensional pits growing in stainless steel foils under electrochemical control in chloride solutions. A method for extracting the key kinetic parameters from radiographs is under development to provide data for validating and calibrating a two-dimensional finite element model previously developed by Laycock and White. The local current density along the boundary of a pit is directly measured from the radiographs. Then, the local metal ion concentration and potential drop inside the pit cavity are backcalculated using transport equations and the requirement to maintain charge neutrality, giving the relationship between current density, solution composition and interfacial potential. Preliminary comparisons show qualitative correlation between the model and extracted data; quantitative comparison is under way. © 2011 Institute of Materials, Minerals and Mining Published by Maney on behalf of the Institute. Source


Ghahari M.,University College Birmingham | Krouse D.,Callaghan Innovation | Laycock N.,University College Birmingham | Rayment T.,Diamond Light Source | And 6 more authors.
Corrosion Science | Year: 2015

In situ synchrotron X-ray radiography was used to observe the evolution of 2D pits growing at the edge of stainless steel foils in chloride solutions of varying concentrations under current and potential control. A method was developed for measuring the local anodic current density along the perimeter of pits from the rate of advance of the pit into the metal. Pit depth tends to increase with time with kinetics consistent with diffusion control (under a salt layer), whereas lateral development (on film-free surfaces) is influenced by solution conductivity. Perforated covers formed on pits control their growth and stability. © 2015 The Authors. Source

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