Stochastic studies of pitting corrosion of stainless steels
Stochastic studies of pitting corrosion of stainless steels
In this thesis a stochastic model for the initiation of pitting corrosion of stainless steel in dilute aqueous chloride media is proposed and developed. The model is formulated with parameters of an initiation frequency for pit nuclei, a death probability for unstable pits, and a critical age which defines the transition between a stable and an unstable pit. The parameters of the model are recovered by analysis of data obtained from observed current-time series. The data analysis methods used are derived from conventional signal analysis techniques and are validated using data obtained by computer simulation of the model. Parameters of the model recovered from experimental data sets are derived as a function of alloy type and environmental conditions. The internal consistency of the model parameters are examined, the adequacy of the general model assessed, and extensions to the model tested by comparison of computer simulations and empirical data. A microscopic model in accord with the observed behaviour is discussed, attributing the initiation of pitting corrosion to the production and persistence of gradients of acidity and electrode potential in the scale of the surface roughness of the metal. Parameters of the stochastic model are identified with elements of the microscopic model with the observed current fluctuations being related to fluctuations in the solution boundary layer thickness. It is proposed that the stability of a pit is dependent on it exceeding a critical depth related to the surface roughness. (D75980/87)
University of Southampton
1987
Westcott, Christopher
(1987)
Stochastic studies of pitting corrosion of stainless steels.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
In this thesis a stochastic model for the initiation of pitting corrosion of stainless steel in dilute aqueous chloride media is proposed and developed. The model is formulated with parameters of an initiation frequency for pit nuclei, a death probability for unstable pits, and a critical age which defines the transition between a stable and an unstable pit. The parameters of the model are recovered by analysis of data obtained from observed current-time series. The data analysis methods used are derived from conventional signal analysis techniques and are validated using data obtained by computer simulation of the model. Parameters of the model recovered from experimental data sets are derived as a function of alloy type and environmental conditions. The internal consistency of the model parameters are examined, the adequacy of the general model assessed, and extensions to the model tested by comparison of computer simulations and empirical data. A microscopic model in accord with the observed behaviour is discussed, attributing the initiation of pitting corrosion to the production and persistence of gradients of acidity and electrode potential in the scale of the surface roughness of the metal. Parameters of the stochastic model are identified with elements of the microscopic model with the observed current fluctuations being related to fluctuations in the solution boundary layer thickness. It is proposed that the stability of a pit is dependent on it exceeding a critical depth related to the surface roughness. (D75980/87)
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Published date: 1987
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Local EPrints ID: 461400
URI: http://eprints.soton.ac.uk/id/eprint/461400
PURE UUID: fb546a9b-74bf-4cbf-96e9-128ea6d6321c
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Date deposited: 04 Jul 2022 18:45
Last modified: 04 Jul 2022 18:45
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Author:
Christopher Westcott
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