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Corrosion Prevention Cathodic System Handbook Corrosion Prevention Cathodic System Handbook on CD CATHODIC CORROSION PROTECTION SYSTEMS. Cathodic protection is an electrochemical method used to prevent or control corrosion. CP systems are active systems that rely on the application of electric current to control corrosion. If current is interrupted, corrosion will progress at a normal rate for the material/environment combination; if supplied current is inadequate for complete protection, corrosion will progress at a reduced rate. After a CP system is installed and adjusted to provide adequate protection, currents and potentials should remain relatively stable; changes in currents or potentials indicate a problem. Works with Windows, Mac, Unix, Linux and others. We find the search feature especially helpful. Search the entire document for a word, phrase or part of a word. Corrosion Prevention Cathodic System Handbook Paragraph 1-1 SCOPE. 1-1 1-2 CATHODIC PROTECTION SYSTEMS. 1-1 1-2.1 Application . 1-1 1-2.2 Benefits . 1-2 1-3 CP SYSTEM MAINTENANCE . 1-2 1-4 CP PROGRAM ELEMENTS . 1-2 CHAPTER 2 PRINCIPLES OF OPERATION Paragraph 3-1 APPLICABLE STANDARDS. 3-1 3-2 DESIGN AND CONSTRUCTION CONSIDERATIONS. 3-1 3-2.1 Ductile Iron Pipe. 3-1 3-2.2 Soil Resistives. 3-1 3-2.3 Joint Bonds . 3-1 3-2.4 Thermite Welds and Exposed Copper Wire. 3-1 3-2.5 Copper . 3-1 3-2.6 Metallic Ferrous Pipe . 3-2 3-2.7 Lightning and Fault Current . 3-2 3-3 SYSTEMS REQUIRING CATHODIC PROTECTION . 3-2 3-3.1 New Piping Systems . 3-3 3-3.2 Existing Piping Systems. 3-3 3-4 SYSTEMS NOT REQUIRING CATHODIC PROTECTION (EXISTING) . 3-3 3-5 FIELD TESTS . 3-3 3-6 DEVIATIONS . 3-3 CHAPTER 4 SCHEDULED PREVENTIVE MAINTENANCE Paragraph 4-1 INTRODUCTION. 4-1 4-2 CLOSE-INTERVAL CORROSION SURVEY . 4-1 4-2.1 Maintenance Intervals. 4-1 4-2.2 Minimum Requirements . 4-1 4-3 CORROSION SURVEY . 4-4 4-3.1 Maintenance Interval. 4-4 4-3.2 Minimum Requirements . 4-4 4-4 WATER TANK CALIBRATION. 4-8 4-4.1 Maintenance Intervals. 4-8 4-4.2 Minimum Requirements . 4-8 4-5 RECTIFIER OPERATIONAL INSPECTION. 4-10 4-5.1 Maintenance Intervals. 4-10 4-5.2 Minimum Requirements . 4-10 4-6 IMPRESSED CURRENT ANODE BED . 4-11 4-7 IMPRESSED CURRENT SYSTEM CHECK . 4-11 4-7.1 Maintenance Intervals. 4-12 4-7.2 Minimum Requirements . 4-12 4-8 GALVANIC ANODE CHECK. 4-12 4-8.1 Procedure . 4-13 4-9 RESISTANCE BOND CHECK . 4-13 4-9.1 Maintenance Interval. 4-13 4-9.2 Minimum Requirements . 4-13 4-10 LEAK SURVEY . 4-14 4-10.1 Maintenance Interval . 4-14 4-10.2 Minimum Requirements . 4-14 4-10.3 Galvanic Anode Systems. 4-15 4-11 RECORD KEEPING REQUIREMENTS. 4-15 CHAPTER 5 UNSCHEDULED MAINTENANCE REQUIREMENTS Paragraph 5-1 INTRODUCTION. 5-1 5-1.1 Troubleshooting . 5-1 5-1.2 Procedures. 5-1 5-2 TROUBLESHOOTING INPRESSED CURRENT SYSTEMS. 5-1 5-2.1 DC Voltage. 5-1 5-2.2 DC Current. 5-4 5-2.3 Anode Lead Wires . 5-7 5-2.4 Structure Lead . 5-7 5-2.5 AC Voltage to Stacks . 5-7 5-2.6 Fuses . 5-8 5-2.7 Diodes. 5-9 5-2.8 Anode Bed . 5-9 5-2.9 Rectifier Taps. 5-10 5-2.10 Rectifier input Voltage. 5-11 5-3 IMPRESSED CURRENT SYSTEM COMMON PROBLEMS. 5-11 5-4 TROUBLESHOOTING GALVANIC (SACRIFICIAL) CATHODIC PROTECTION SYSTEMS . 5-13 5-4.1 Common Problems . 5-13 5-4.2 Lead Wires. 5-13 5-4.3 Anode Consumption. 5-13 5-4.4 Improper Use . 5-13 5-5 INTERFERENCE TESTING.5-13 5-6 INTERFERENCE CORROSION CONTROL. 5-14 5-6.1 Correcting Interference . 5-14 5-6.2 Direct Bonding . 5-14 5-6.3 Bonding. 5-15 5-6.4 Installing a Sacrificial Anode . 5-15 5-6.5 Additional Coating. 5-17 5-6.6 Installation of Nonmetallic Sections or Isolations. 5-18 5-6.7 Application of a Small Impressed Current System. 5-18 5-6.8 Combination of Techniques . 5-18 CHAPTER 6 INSPECTION PROCEDURES AND CRITERIA Paragraph 6-1 INTRODUCTION. 6-1 6-1.1 Methods . 6-1 6-2 APPLICABILITY. 6-1 6-3 CRITERIA . 6-2 6-3.1 Steel and Cast Iron Piping . 6-2 6-3.2 Special Conditions . 6-3 6-3.3 Aluminum Piping . 6-4 6-3.4 Copper Piping . 6-4 6-3.5 Dissimilar Metal Piping. 6-4 6-4 OTHER CONSIDERATIONS . 6-4 6-4.1 Determining Voltage Drops. 6-5 6-4.2 Sound Engineering Practices. 6-5 6-4.3 In-Line Inspection of Pipes. 6-5 6-4.4 Stray Currents and Stray Electrical Gradients . 6-5 6-5 ALTERNATIVE REFERENCE ELECTRODES . 6-5 6-5.1 Alternative to Saturated Copper / Copper Sulfate . 6-5 6-5.2 Alternative Metallic Material or Structure . 6-5 Paragraph 7-1 POTENTIAL MEASUREMENT . 7-1 7-2 SOURCES OF ERROR . 7-1 7-2.1 Accuracy of the Reference Electrode. 7-1 7-2.2 IR Drop Error. 7-3 7-2.3 Anode Gradient Error. 7-4 7-2.4 Contact Resistance Error. 7-5 7-2.5 Mixed Potential Error. 7-6 7-3 PRACTICAL MEASUREMENT OF CATHODIC PROTECTION POTENTIALS. 7-7 7-3.1 Test Criteria Selection. 7-7 7-3.2 Test Methods for the -0.85 ON Criterion . 7-9 7-3.3 Test Methods for the -0.85 Instant-OFF Criterion . 7-11 7-3.4 Test Methods for the 100mV Polarization Criterion . 7-11 7-3.5 Instant-OFF Test Methods . 7-11 7-3.6 Types of Interrupters. 7-12 7-3.7 Specific Methods for Various Instant-OFF Potential Measurement Techniques . 7-13 7-4 STRUCTURE-TO-SOIL POTENTIAL LIMITS. 7-17 7-4.1 Excessive Cathodic Protection Current. 7-17 7-4.2 Water Storage Tanks . 7-18 7-4.3 Underground Structures. 7-18 7-4.4 Uncoated Structures . 7-19 7-5 CELL-TO-CELL POTENTIAL TESTING PROCEDURES. 7-19 7-5.1 Performing Test. 7-19 7-5.2 Accuracy . 7-20 7-6 RECTIFIER EFFICIENCY TESTING PROCEDURES. 7-21 7-6.1 Determining Efficiency . 7-21 7-6.2 Alternate Procedure . 7-21 7-6.3 Expected Efficiency. 7-22 7-7 DIELECTRIC TESTING PROCEDURES. 7-22 7-7.1 Testing for a Shorted Dielectric. 7-23 7-7.2 Using a Radio Frequency Tester . 7-25 7-7.3 Using a Pipe Locator. 7-25 7-7.4 Using a Temporary Local Cathodic Protection System. 7-27 7-8 CASING TESTS.7-27 7-8.1 Testing a Casing with Cathodic Protection on the Carrier Pipeline. 7-28 7-8.2 Testing a Casing without Cathodic Protection on the Carrier Pipeline .7-30 7-9 TESTING FOR A SHORT BETWEEN TWO STRUCTURES . 7-30 7-9.1 Testing for a Short Between Two Structures with Cathodic Protection on One Structure . 7-31 7-9.2 Testing for a Short Between Two Structures with Cathodic Protection on Both Structures. 7-33 7-9.3 Testing for a Short Between Two Structures without Cathodic Protection on Either Structure. 7-36 7-10 CURRENT REQUIREMENT TESTING PROCEDURES . 7-38 7-10.1 Temporary Local Cathodic Protection Systems . 7-38 7-10.2 Existing Metallic Structures. 7-39 7-10.3 Temporary Anodes. 7-39 7-10.4 Installation of Temporary Anode System . 7-39 7-10.5 Connections . 7-40 7-10.6 Before Applying Power. 7-40 7-10.7 Applying Power . 7-40 7-10.8 Sufficient Current . 7-40 7-10.9 Calculating Current Requirements . 7-40 7-10.10 More than One Anode Bed . 7-41 7-10.11 Completion of Testing . 7-41 7-11 ELECTROLYTE RESISTIVITY MEASUREMENT . 7-41 7-11.1 Four-Pin Method . 7-42 7-11.2 Two-Pin Method. 7-43 7-11.3 Other Methods (Soil Rod, Soil Box) . 7-44 7-12 pH TESTING PROCEDURES. 7-45 7-12.1 Antimony Electrode Test Method. 7-46 7-12.2 Chemical Test Method . 7-48 7-13 CALIBRATION OF IR DROP TEST SPAN . 7-48 7-13.1 Measurement Circuits . 7-50 7-13.2 Direction of Current Flow . 7-51 7-13.3 Resistance of the Pipeline . 7-52 7-13.4 Multi-Combination Meter. 7-54 7-14 INTERFERENCE TESTING PROCEDURES . 7-55 7-14.1 Interference from Cathodic Protection Rectifiers . 7-55 7-14.2 Interference from Variable (Fluctuating) Sources . 7-59 2-1 The Corrosion Cell. 2-3 2-2 Corrosion Cell, The Dry Cell battery . 2-3 2-3 Concentration Cell Caused by Different Environments. 2-7 2-4 Concentration Cell Caused by Different Concentrations of Oxygen . 2-8 2-5 Concentration Cell Caused by Different Concentrations of Water. 2-8 2-6 Concentration Cell Caused by Non-Homogenous Soil . 2-9 2-7 Concentration Cell Caused by Concrete and Soil Electrolytes .2-10 2-8 Galvanic Corrosion Cell Caused by Different Metals.2-11 2-9 Galvanic Corrosion Cell Caused by Old and New Steel .2-12 2-10 Galvanic Corrosion Cell Caused by Marred and Scratched Surfaces .2-13 2-11 Combination of Many Different Corrosion Cells at Work .2-14 2-12 Stray Current Corrosion Cell Caused by External Anode and Cathode.2-15 2-13 Stray Current Corrosion Cell Caused by a DC Transit System .2-17 2-14 Stray Current Corrosion Cell Caused by an HVDC Transmission System 2-18 2-15 Stray Current Corrosion Cell Caused by a DC Welding Operation.2-18 2-16 Stray Current Corrosion Cell Caused by a Cathodic Protection System .2-19 2-17 Effect of Electrolyte pH on the Rate of Corrosion .2-22 2-18 Direct Attachment Galvanic (Sacrificial) Cathodic Protection System .2-29 2-19 Distributed Sacrificial (Galvanic) Cathodic Protection System.2-30 2-20 Galvanic Anode Installation .2-38 2-21 Above Grade Test Station .2-39 2-22 Subsurface Test Station .2-40 2-23 Potential Current Test Station Connections.2-40 2-24 Impressed Current Cathodic Protection System.2-42 2-25 Impressed Current Cathodic Protection System Rectifier.2-44 2-26 Vertical Remote Impressed Current Cathodic Protection System .2-53 2-27 Horizontal Remote Impressed Current Cathodic Protection System .2-54 2-28 Distributed Impressed Current Cathodic Protection System.2-55 2-29 Deep Remote Impressed Current Cathodic Protection System.2-56 2-30 Flush Test Station.2-57 2-31 Abovegrade Test Station .2-58 5-1 Troubleshooting Block Diagram. 5-2 5-2 Typical Rectifier Wiring Diagram . 5-4 5-3 Shunt Multiplication Factors . 5-5 5-4 Correction of Interference by Resistive Bonding .5-15 5-5 Bonding for Continuity .5-16 5-6 Use of Galvanic Anodes to Control Interference .5-16 5-7 Use of Coating Cathode to Control Interference.5-17 5-8 Use of Isolation on Foreign Structure to Control Interference.5-18 5-9 Use of a Combination of Mitigation Techniques to Control Interference.5-19 7-1 Copper/Copper Sulfate Reference Electrode (Half-Cell) . 7-2 7-2 IR Drop Error . 7-4 7-3 Anode Gradient Error . 7-5 7-4 Contact Resistance Error . 7-6 7-5 Mixed Potential Error . 7-7 7-6 Single Electrode Potential Survey . 7-9 7-7 Typical Displayed Readings Using Digital Voltmeter .7-14 7-8 Readings Recorded by Digital Voltmeter with Minimum/Maximum Function.7-15 7-9 Examples of Voltage Spiking on Instant-OFF Readings .7-16 7-10 Positive Reading for Cell-to-Cell Survey.7-20 7-11 Negative Reading for Cell-to-Cell Survey .7-21 7-12 Rectifier Efficiency .7-22 7-13 Testing for a Shorted Dielectric .7-23 7-14 Testing an Installed Dielectric with the Insulated Flange Tester.7-25 7-15 Testing for a Shorted Dielectric using a Pipe Locator.7-26 7-16 Testing for Shorted Dielectric with Power Supply .7-27 7-17 Typical Casing Installation.7-28 7-18 Testing for a Shorted Casing.7-29 7-19 Testing for a Shorted Casing with Power Supply.7-30 7-20 Testing for a Short Between Two Structures .7-32 7-21 Testing for a Short Between Two Structures with Power Supply.7-33 7-22 Testing for a Short Between Two Structures with Cathodic Protection on Both Structures.7-34 7-23 Testing for a Short Between Two Structures without Cathodic Protection on Either Structure .7-36 7-24 Testing for a Short Between Two Structures with Power Supply.7-38 7-25 Removing Temporary Anodes (Ground Rods) .7-41 7-26 Soil Resistivity by the Four Pin Method (Wenner) .7-42 7-27 Two-Pin Method (Shepard’s Canes) of Soil Resistivity Measurement .7-44 7-28 Soil Resistivity Measurement Using a Soil Rod .7-44 7-29 Soil Resistivity Measurement Using a Soil Box .7-45 7-30 Effect of pH on the Corrosion Rate of Steel.7-46 7-31 Antimony Electrode .7-47 7-32 pH Measurement with Electrolyte Current Flow .7-48 7-33 Typical IR Drop Test Span Installation .7-49 7-34 Calibration of an IR Drop Test Span.7-50 7-35 IR Drop Test Span, Direction of Current Flow .7-52 7-36 Null Ammeter Method, Using the Multi-Combination Meter.7-54 7-37 Cell-to-Cell Polarity on Foreign Structure .7-57 7-38 Normal and Abnormal Potentials of Protected and Foreign Pipelines .7-58 2-1 Weight Loss of Specific Metals at a Current of One Ampere for One Year (1 Amp-Year) .2-16 2-2 Electrical Potential of Metals With Various Reference Cells.2-24 2-3 Current Requirements for Cathodic Protection of Bare Steel .2-26 2-4 Current Requirements for Cathodic Protection of Coated Steel .2-27 2-5 Composition of Magnesium Anodes.2-31 2-6 Composition of Zinc Anodes.2-32 2-7 Composition of Aluminum Anodes.2-33 2-8 Sacrificial Anodes Available Voltage for Cathodic Protection .2-34 2-9 Estimated Output Current of Sacrificial Anodes .2-35 2-10 Applicable Tables in MIL-HDBK-1004/10 .2-36 2-11 Electrochemical Equivalents of Common Structural Metals .2-45 2-12 Cast Iron Composition.2-46 2-13 Cast Iron Anodes.2-47 2-14 .2-52 4-1 Close-Interval Survey CP System Component Testing Requirements . 4-2 4-2 Close-interval Survey Potential Measurement Locations . 4-3 4-3 Corrosion Survey Component Testing.4-5 4-4 Corrosion Survey Potential Measurements .4-6 4-5 Water Tank Calibration CP System Component Tests.4-9 4-6 Water Tank Calibration Potential Measurements .4-9 4-7 Recommended Over-the-Anode Intervals for the Impressed Current Anode Bed Survey .4-11 4-8 Recommended Corrective Actions for Preventing Leaks .4-15 5-1 Common Impressed Current Rectifier Problems .5-12 7-1 Potential Limits for Underground Coated Structures .7-19 7-2 Expected Potential Example Under Shorted/Not Shorted Conditions. 7-35 7-3 Four-Pin soil Resistivity Measurement Reading Multipliers . 7-43 7-4 Estimated Resistance of Steel Pipelines . 7-53 All material in Adobe PDF format. 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