This research studied hydrogen damage susceptibility (e.g., cracking and pitting) of steel pipe due to the effect on magnetism in combination with cathodic protection. This recent phase (Phase III) of research built on findings made during Phase I that ended in December 2005 (TAP Study 487) and Phase II that ended in February 2007 (TAP Study 522). During the prior studies, CSM found evidence of hydrogen cracking and surface pitting due to hydrogen absorption during cathodic protection under strong magnetic fields; magnetic levels typically found in some 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 (e.g., MFL-tools), the US DOT PHMSA and US DOI BOEMRE 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 BOEMRE) and representatives from the Norwegian Pipeline Industry and based on those discussions received support to proceed with Phase III for further test analysis under laboratory and actual field conditions to (in)validate the findings form the prior studies.
This study (Phase III) was complete in December 2010 and resulted in the following findings and recommendations:
Primary Findings:
(1) Confirmed that Hydrogen absorption under magnetism leads to increased surface pitting and hydrogen cracking,
(2) Confirmed that hydrogen content increases with increasing magnetic field strength, and
(3) Magnetic field alters the corrosion behavior of X80, X70, and X52 by shifting the passive potential in the positive direction, therefore, an increase in corrosion susceptibility.
Recommendations:
Further investigation to more thoroughly provide guidelines for industry as follows: (1) Quantification of the formation of passive films at cathodic potentials.
(2) Quantification of the effect of magnetic field on electrode kinetics.
(3) Development of protocol for the industry for insitu measurement of hydrogen and magnetic field remanence.
(4) Development of procedure to mitigate generation of remnant magnetic fields in pipelines. Additional information regarding this study's work and findings can be found within the final report provided below .