PPiippeelliinnee CCoorrrroossiioonn FINAL REPORT Submitted to U.S. Department of Transportation Pipeline and Hazardous Materials Safety Administration Office of Pipeline Safety Integrity Management Program Under Delivery Order DTRS56-02-D-70036 Submitted by Michael Baker Jr., Inc. Contributing Author Raymond R. Fessler, Ph.D. BIZTEK Consulting, Inc. November 2008 Table of Contents Table of Contents 1 Introduction...........................................................................................................................................1 1.1 Corrosion Overview ....................................................................................................................1 1.2 Corrosion in Perspective..............................................................................................................2 1.2.1 Frequency and Consequences in the United States.................................................................2 1.2.2 Transmission Pipelines............................................................................................................3 1.2.3 Natural Gas Distribution Pipelines..........................................................................................5 1.2.4 Gas Gathering Lines................................................................................................................6 1.2.5 Non-U.S. Experience ..............................................................................................................6 1.3 State of Knowledge Regarding Corrosion...................................................................................8 2 Background.........................................................................................................................................10 2.1 Problem Statement.....................................................................................................................10 2.2 Project Scope.............................................................................................................................10 2.3 Report Outline ...........................................................................................................................10 3 Corrosion in Pipelines.........................................................................................................................11 3.1 Understanding the Process.........................................................................................................11 3.2 Uniform vs. Localized Corrosion ..............................................................................................12 3.2.1 Pitting ....................................................................................................................................12 3.2.2 Selective Seam Corrosion .....................................................................................................13 3.2.3 Microbial Corrosion..............................................................................................................13 3.3 External Corrosion.....................................................................................................................14 3.3.1 Factors that Affect External Corrosion .................................................................................14 3.3.1.1 Onshore Buried Pipelines.............................................................................................14 3.3.1.2 Offshore Pipelines ........................................................................................................15 3.3.2 Methods to Prevent or Mitigate External Corrosion on Buried Pipelines.............................15 3.3.2.1 Coatings........................................................................................................................15 3.3.2.2 Cathodic Protection ......................................................................................................19 3.3.2.3 Other Preventive/Mitigative Measures.........................................................................20 3.3.3 Monitoring Techniques for External Corrosion ....................................................................21 3.4 Internal Corrosion......................................................................................................................22 3.4.1 Gas Pipelines.........................................................................................................................22 3.4.2 Liquid Pipelines ....................................................................................................................22 3.4.3 Preventive/Mitigative Measures for Internal Corrosion........................................................23 3.4.3.1 Dehydration ..................................................................................................................23 3.4.3.2 Inhibitors ......................................................................................................................24 3.4.3.3 Coatings........................................................................................................................24 3.4.3.4 Buffering ......................................................................................................................24 3.4.3.5 Cleaning Pigs................................................................................................................24 3.4.3.6 Biocides ........................................................................................................................24 3.4.3.7 Additional Preventive Measures...................................................................................25 3.4.3.8 Preventive/Mitigative Measures for Selective Seam Corrosion...................................25 3.4.3.9 Preventive/Mitigative Measures for MIC on Gas Pipelines.........................................25 3.4.4 Monitoring Internal Corrosion ..............................................................................................25 3.5 Environmentally Assisted Cracking ..........................................................................................26 3.5.1 Stress-Corrosion Cracking (SCC) .........................................................................................26 3.5.1.1 External SCC................................................................................................................26 3.5.1.2 Internal SCC .................................................................................................................27 3.5.2 Corrosion Fatigue..................................................................................................................27 Pipeline Corrosion November 2008 Page i Table of Contents 3.5.3 Hydrogen Embrittlement.......................................................................................................28 3.5.3.1 Hydrogen-Stress Cracking............................................................................................28 3.5.3.2 Hydrogen-Induced Cracking ........................................................................................29 3.5.3.3 Loss of Ductility...........................................................................................................29 3.5.3.4 Implications for Pipelines in a National Hydrogen Economy ......................................29 3.5.4 Sulfide-Stress Cracking.........................................................................................................29 4 Corrosion Threat Identification...........................................................................................................31 4.1 Overview ...................................................................................................................................31 4.2 External Corrosion.....................................................................................................................31 4.3 Internal Corrosion......................................................................................................................31 4.4 Stress Corrosion Cracking.........................................................................................................31 5 Corrosion Damage-Assessment Methods ...........................................................................................33 5.1 Overview ...................................................................................................................................33 5.2 In-line Inspection.......................................................................................................................33 5.3 Hydrostatic Testing ...................................................................................................................35 5.4 Direct Assessment .....................................................................................................................36 5.4.1 External Corrosion Direct Assessment .................................................................................37 5.4.2 Internal Corrosion Direct Assessment for Gas Pipelines ......................................................38 5.4.3 Stress Corrosion Cracking Direct Assessment......................................................................40 5.5 Emerging Technologies.............................................................................................................40 5.5.1 Long-Range Guided-Wave Ultrasonic Testing (LRGWUT or GWUT)...............................40 5.5.2 Remote Field Testing (RFT)