Intermediate Course Appalachian Underground Corrosion Short Course West Virginia University Morgantown, West Virginia Copyright © 2017 APPALACHIAN UNDERGROUND CORROSION SHORT COURSE INTERMEDIATE COURSE CHAPTER 1 ‐ CORROSION CELLS IN ACTION............................. 1‐1 INTRODUCTION................................................. 1‐1 REVIEW OF BASIC CONCEPTS...................................... 1‐1 Basic Course Reference........................................ 1‐1 A Corrosion Cell Concept....................................... 1‐1 Dry Cell Example of a Corrosion Cell.............................. 1‐3 DEMONSTRATION............................................... 1‐5 Dissimilar Metal Corrosion Cell.................................. 1‐6 Corrosion Cell Showing Effect of Electrolyte pH Characteristics on Dissimilar Metal Corrosion.............................................. 1‐7 Corrosion Cell Demonstrating Corrosion Caused by Differential Oxygen Concentration................................................ 1‐8 Corrosion Cell Demonstrating Corrosion Caused by Dissimilar Surface Conditions on Steel ........................................... 1‐9 Demonstration Showing the Corrosion Cell Resulting from Differences in Electrolyte Concentration..................................... 1‐10 Demonstration to Show the Effect of Anode‐Cathode Ratio on Corrosion Rate....................................................... 1‐11 Demonstration to Show the Corrosive Effect of Stress in Metal . .... 1‐13 Demonstration to Show Effect of Cathodic Protection on a Corrosion Cell........................................................ 1‐14 Demonstration Flexibility ..................................... 1‐15 Demonstration Equipment .................................... 1‐15 CONCLUSIONS................................................. 1‐17 CHAPTER 2 ‐ INSTALLATION OF GALVANIC ANODES ...................... 2‐1 INTRODUCTION................................................. 2‐1 REVIEW OF FUNDAMENTALS...................................... 2‐1 The Galvanic Corrosion Cell.....................................2‐1 Galvanic Anodes and Cathodic Protection.........................2‐2 Galvanic Anodes Plus Coatings and Electrical Isolation............... 2‐2 GALVANIC ANODE APPLICATIONS .................................. 2‐3 General Uses................................................. 2‐3 Specific Uses................................................. 2‐4 Advantages and Disadvantages ................................. 2‐7 GALVANIC ANODE CHARACTERISTICS ............................... 2‐8 Galvanic Anode Materials...................................... 2‐8 Magnesium Anodes........................................... 2‐8 Zinc Anodes ................................................. 2‐9 Aluminum Anodes ........................................... 2‐10 Use of Special Chemical Backfill ................................2‐10 GALVANIC ANODE INSTALLATION PROCEDURES ..................... 2‐12 Single Anode Installation...................................... 2‐12 Multiple Anode Installation.................................... 2‐12 Anode Lead Attachment ...................................... 2‐13 Test Points ................................................. 2‐13 CONCLUSIONS................................................. 2‐13 CHAPTER 3 ‐ INSTALLATION OF IMPRESSED CURRENT CATHODIC PROTECTION SYSTEMS..............................................3‐1 INTRODUCTION................................................. 3‐1 DEFINITIONS ................................................... 3‐1 Impressed Current Cathodic Protection System ....................3‐1 Remote Anode Bed ........................................... 3‐1 Distributed Anode Bed ........................................ 3‐2 Deep Anode Bed.............................................. 3‐3 POWER SUPPLIES FOR IMPRESSED CURRENT CATHODIC PROTECTION SYSTEMS....................................................... 3‐3 Rectifiers.................................................... 3‐3 Solar Cells................................................... 3‐4 Thermoelectric Generators..................................... 3‐5 Engine ‐ Generator Sets........................................ 3‐5 Turbine ‐ Generator Sets....................................... 3‐5 Wind Powered Generators ..................................... 3‐5 ANODE BED MATERIALS.......................................... 3‐6 Anodes ..................................................... 3‐6 Packaged Anodes............................................. 3‐8 Anode‐Lead Connection Insulation............................... 3‐8 Cables ...................................................... 3‐8 Cable Connections............................................ 3‐9 Cable Splices and Repairs ...................................... 3‐9 SELECTING AN ANODE BED SITE................................... 3‐10 Soil Resistivity............................................... 3‐10 Soil Moisture ............................................... 3‐11 Interference with Foreign Structures............................3‐11 Power Supply Availability ..................................... 3‐12 Accessibility for Maintenance and Testing ........................ 3‐12 Vandalism.................................................. 3‐12 Purpose of Anode Bed and Site Availability ....................... 3‐13 INSTALLATION PRACTICES ....................................... 3‐13 Anodes ‐ General............................................ 3‐13 Vertical Installation .......................................... 3‐14 Horizontal Installation........................................ 3‐14 Deep Anode Installation ...................................... 3‐15 Cable Installation............................................ 3‐15 Rectifier Installation..........................................3‐16 CONCLUSIONS................................................. 3‐17 CHAPTER 4 ‐ CRITERIA FOR CATHODIC PROTECTION...................... 4‐1 INTRODUCTION................................................. 4‐1 CRITERIA FOR STEEL AND CAST IRON PIPING .........................4‐1 ‐850 mV with the Cathodic Protection Applied Criterion ............. 4‐2 Application ............................................... 4‐2 Limitations................................................ 4‐3 Polarized Potential of ‐850 mV Criterion .......................... 4‐5 Application ............................................... 4‐5 Limitations................................................ 4‐6 100 mV of Polarization Criterion ................................. 4‐7 Application ............................................... 4‐9 Limitations................................................ 4‐9 Cathodic Protection Coupons.................................. 4‐10 Net Protective Current Criterion................................4‐11 Application .............................................. 4‐12 Limitations............................................... 4‐12 Other Criteria For Steel And Cast Iron .......................... 4‐13 300 mV Potential Shift Criterion ................................ 4‐13 E‐Log I Curve Criterion........................................ 4‐14 CRITERION FOR ALUMINUM PIPING ............................... 4‐15 CRITERION FOR COPPER PIPING................................... 4‐16 CRITERION FOR DISSIMILAR METAL PIPING ......................... 4‐17 CHAPTER 5 ‐ STATIC STRAY CURRENT INTERFERENCE TESTING ............. 5‐1 INTRODUCTION................................................. 5‐1 DEFINITIONS ................................................... 5‐1 STATIC INTERFERENCE ........................................... 5‐2 INTERPRETATION OF DATA........................................ 5‐3 Finding the Source of Static Interference.......................... 5‐6 Determining the Point of Maximum Exposure ..................... 5‐7 MITIGATION OF STATIC INTERFERENCE.............................. 5‐8 Mitigation by Bonds........................................... 5‐8 Mitigation by Addition of Cathodic Protection ..................... 5‐9 Natural Potential Criterion .................................... 5‐10 TYPICAL EXAMPLES OF STATIC INTERFERENCE....................... 5‐11 Summary of Examples........................................ 5‐17 Things to Watch Out For...................................... 5‐17 CHAPTER 6 ‐ CORROSION CONTROL FOR PIPELINES ...................... 6‐1 INTRODUCTION................................................. 6‐1 PREFACE....................................................... 6‐1 COATINGS...................................................... 6‐2 History of the Use of Coating Systems............................ 6‐2 General..................................................... 6‐3 Types of Underground Coatings ................................. 6‐4 Enamels..................................................... 6‐5 Fusion Bonded Epoxy ‐ FBE..................................... 6‐6 Extruded Plastic Coatings ...................................... 6‐7 Hot Applied Mastics........................................... 6‐8 Cold Liquid Coatings........................................... 6‐9 Two Part Epoxy Coatings...................................... 6‐10 Hot Applied Waxes........................................... 6‐11 Cold Applied Wax............................................ 6‐12 Prefabricated Films and Tapes ................................. 6‐13 Heat Shrink Sleeves and Tapes................................. 6‐14 Directional Drilled Crossings ................................... 6‐14 Desired