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51318-10847- A Critical Review of Parameters for Meaningful AC Corrosion Modelling

Picture for 51318-10847- A Critical Review of Parameters for Meaningful AC Corrosion Modelling
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The present paper presents and discusses the various components contained in an electrical equivalent circuit describing the AC corrosion process from a computer modelling perspective.

Product Number: 51318-10847-SG
Author: Ernesto Santana-Diaz / Andreas Junker-Holst / Lars Vendelbo Nielsen
Publication Date: 2018
Industry: Science of Corrosion
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$20.00

A range of parameters must be considered carefully when modelling AC corrosion. Prediction of induced AC voltage profiles along pipelines due to shared right-of-way with high-voltage power lines has been practiced for decades. Modelling of the cathodic protection level on a pipeline resulting from types, position, and current output from CP sources, pipeline dimensions, coating conditions, soil conditions, isolation, etc., has also been implemented during several years. Computer aided prediction of corrosion rates caused by induced AC as a function of AC and DC current densities, coating fault geometry and thickness, soil resistivity, etc. has been attempted only in recent years. The complexity of the AC corrosion process calls for careful and critical evaluation of the computed results, and their practical applicability.

The present paper presents and discusses the various components contained in an electrical equivalent circuit describing the AC corrosion process from a computer modelling perspective. The effect of the coating defect size and geometry on spread resistance and resulting AC current density, the effect of the kinetics of electrochemical reactions relevant for the corrosion process, the effect of diffusion and diffusion coefficients for active chemical species, as well as the impact of the capacitive effect of the electrochemical double layer as a short circuit of the electrochemical processes, soil chemistry, texture and soil resistivity are all aspects that influences the AC corrosion process and therefore the reliability of a computer model. These aspects will be discussed together with the sensibility of a model and the risk of generating inaccurate results due to missing or erroneous inputs. In addition, different model approaches will be discussed and sustained through examples.

Key words: AC corrosion, cathodic protection, coating defect, computer modelling, pipeline integrity

A range of parameters must be considered carefully when modelling AC corrosion. Prediction of induced AC voltage profiles along pipelines due to shared right-of-way with high-voltage power lines has been practiced for decades. Modelling of the cathodic protection level on a pipeline resulting from types, position, and current output from CP sources, pipeline dimensions, coating conditions, soil conditions, isolation, etc., has also been implemented during several years. Computer aided prediction of corrosion rates caused by induced AC as a function of AC and DC current densities, coating fault geometry and thickness, soil resistivity, etc. has been attempted only in recent years. The complexity of the AC corrosion process calls for careful and critical evaluation of the computed results, and their practical applicability.

The present paper presents and discusses the various components contained in an electrical equivalent circuit describing the AC corrosion process from a computer modelling perspective. The effect of the coating defect size and geometry on spread resistance and resulting AC current density, the effect of the kinetics of electrochemical reactions relevant for the corrosion process, the effect of diffusion and diffusion coefficients for active chemical species, as well as the impact of the capacitive effect of the electrochemical double layer as a short circuit of the electrochemical processes, soil chemistry, texture and soil resistivity are all aspects that influences the AC corrosion process and therefore the reliability of a computer model. These aspects will be discussed together with the sensibility of a model and the risk of generating inaccurate results due to missing or erroneous inputs. In addition, different model approaches will be discussed and sustained through examples.

Key words: AC corrosion, cathodic protection, coating defect, computer modelling, pipeline integrity

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51318-10911-Field Examination of AC Accelerated Corrosion Featured in Monitored Locations

Product Number: 51318-10911-SG
Author: Shane Finneran, P.E. / Dr. Dave Norfleet / Lyle Buckingham
Publication Date: 2018
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AC current density (rather than voltage alone) should always be the factor considered when assessing susceptibility to AC corrosion. Also presented are analyses used in assessing the metal loss features and the comparison of site-specific data.
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51318-10676-Research on the Effects of Environmental Parameters on AC Corrosion Behavior

Product Number: 51318-10676-SG
Author: Yanxia Du / Sili Xie / Yingwu Xiao / Minxu Lu
Publication Date: 2018
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AC corrosion experiments were done on two kinds of typical soil simulants with different contents of (Ca2+), (Mg2+) and (Na+) to study the effects of environmental and cathodic protection parameters on AC corrosion rates.
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51318-10898- Comparison of AC Mitigation Grounding Materials Through Electrochemical Analysis

Product Number: 51318-10898-SG
Author: Shane Finneran, P.E. / Ken Evans / Justin Gossard
Publication Date: 2018
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A comparative assessment of electrochemical properties of common AC mitigation materials, and assessment of common industry claims with respect to AC mitigation grounding. Provides the corrosion test data and technical information to support a decision for mitigation material selection.
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