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| Project Number | 576 |
| Date of Summary | December 3, 2008 |
| Subject | Measurement of the Effect of Magnetism on Hydrogen Cracking Susceptibility of Pipeline Steels |
| Performing Activity | Colorado School of Mines (CSM) |
| Principal Investigator | Dr. David Olson |
| Contracting Agency | Minerals Management Service |
| Estimated Completion | August 31, 2010 |
| Description | This research serves to study hydrogen damage susceptibility (i.e., cracking and pitting) of steel pipe due to the effect on magnetism (including remnant magnetism) in combination with cathodic protection. The current phase (Phase III) of research will build on findings made during phase I that ended in December 2005 (TAR Study 487) and Phase II that ended in February 2007 (TAR Study 522). CSM found evidence of hydrogen cracking and surface pitting due to hydrogen absorption from cathodic protection under strong magnetic fields; magnetic levels typically found in many pipeline integrity tools used by industry. Due to concerns for these findings and the implications to industry’s use of internal pipeline inspection integrity tools (i.e., MFL-tools), the DOT and MMS asked that CSM solicit comments from Industry as to CSM’s findings and the need for additional analysis. CSM held a series of meetings for that purpose with representatives from Industry, Academia, the Federal Government (NIST, PHMSA, and MMS) and representatives from the Norwegian Pipeline Industry and based on those discussion received support to proceed with Phase III for further test analysis to (in)validate the findings using actual field conditions under a Joint Industry Project. |
| Progress |
Modeling of the underlying effects of magneto corrosion behavior has coupled electromagnetic perturbations to alterations in the electrochemical behavior, including the Helmholtz and Gouy-Chapman layer. These perturbations result in enhanced anodic and cathodic behavior, resulting in both increase in hydrogen ingress and pitting and cracking behavior. Findings to date include: 1. Magnetic fields may cause a significant increase in the corrosion, as indicated by pitting and cracking assessment, and hydrogen content measurements over time. 2. Magnetic properties measurements suggest significant remanence may exist even at relatively low applied magnetic field levels. 3. Thermodynamics calculations based on the various internal and external works involved with magnetic fields suggest that spin magnetization internal work is insufficient to explain the enhanced magnetocorrosion. Magnetostriction and solute-strain models have been described, and a significant contribution to the Helmholtz Free Energy from those terms would be required to explain the enhanced corrosion observed in magnetocorrosion by thermodynamics. 4. Kinetic models, based on electromagnetic stirring in both the metal and the electrolyte, suggest a possible explanation for the enhanced magnetocorrosion behavior. 5. Electrochemical impedance spectroscopy provides a sensitive measurement for assessment of surface corrosion. Magnetic fields cause a significant shift in the measured electrochemical impedance spectroscopy of pipeline steels, which suggests a stirring mechanism may be occurring in both near-electrolyte region (magnetohydrodynamics) and in the metal (Lorentz forces). 6. The magnetohydrodynamic stirring assists in transport of hydrogen to the steel surface. 7. Lorentz forces assist in the transport of hydrogen from the metal surface into the bulk metal, suggesting enhanced hydrogen concentrations based on kinetics. |
| Report | |
AA  (7961
KB) |
1. Measurement of the Effect of Magnetism on Hydrogen Cracking Susceptibility of Pipeline Steels, Progress Report by Dr. David L. Olson, Dr. Brajendra Mishra, and J. A. Boubidoux, Colorado School of Mines, Golden, CO, November 2008. |
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