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Preface to Third Edition vii Preface to First Edition ix 1 Soil Resistivity Surveys 1 Soil Resistivity Units. Two-Terminal Resistivity Determination. Four- Terminal Resistivity Determination. Other Methods. Locating Hot Spots on Bare Lines. Surveys for Ground Beds. Area Surveys. Logarithmic Resistivity Ranges. Summary. 2 Potential Surveys 16 Pipe-to-Soil Potentials: Electrodes. Electrode Placement. Pipe Line Connection. Surface Potential Survey for Corrosion. Pipe-to-Soil Potential as a Criterion of Cathodic Protection. Other Applications of Pipe-to-Soil Potentials. Other Criteria. Summary. 3 Line Currents 31 Measurement of Line Current in Test Section. Stray-Current Studies. Long-Line Currents. Cathodic Protection Tests. Coating Conductance Measurement. Summary. 4 Current Requirement Surveys 36 The Problem: Coated Lines. Principles of Current Requirement Test. Current Sources for Tests. Temporary Ground Beds. Special Conditions. Summary. 5 Rectifier Systems for Coated Lines 45 General Design Principles. Attenuation Curves. Line Termination. Anode Proximity Effects. Attenuation with Multiple Drain Points. Design Procedure. An Alternate Method. The Economic Balance. Summary. v 6 Ground Bed Design and Installation 59 Design Principles. Disturbing Factors. Field Modification. Installation Methods. High-Silicon Iron Anodes. Steel Anodes. Horizontal Graphite Anodes. Deep Anodes. A Typical Ground Bed Installation. Summary. 7 Galvanic Anodes on Coated Lines 78 When and Where to Use Magnesium. When and Where to Use Zinc. General System Design. Installation Procedure. Polarization and Final Adjustment. Modification of Process with Experience. Sample Problems. Summary. 8 Hot Spot Protection 88 What "Hot Spots" Are. Hot Spot Protection. Locating Hot Spots. Anode Selection and Spacing. Field Installation. Field Design. Zinc Anodes in Hot Spot Protection. Installation Details. Supervision and Control. Summary. 9 Stray-Current Electrolysis 100 Stray Current Corrosion. Sources of Stray Currents. Detection of Stray Current. Remedial Measures. Negative Bus Bonding. Exposure Areas. Potential Surveys. Secondary Exposure. Summary. 10 Interference in Cathodic Protection 109 The Problem. Basic Solutions. Design. Crossing Bonds. Calculation of Bond Resistance. Multiple Bonds. Auxiliary Drainage. Parallel Lines. Radial-Flow Interference. Foreign Lines with Insulating Joints. Summary. 11 Operation and Maintenance 125 Importance of Adequate Supervision. Failures in Rectifier-Ground Bed Systems. Failures in Magnesium Anode Systems. Minimum Inspection Schedule for Rectifier System. Minimum Inspection Schedule for Anodes. Monitor System. Troubleshooting. Summary. 12 Coating Inspection and Testing 136 Construction Inspection. Evaluation of Coating in Place. Coating or Leakage Conductance. Pearson Surveys. Accelerated Coating Tests. Summary. Appendix A Fundamentals of Corrosion 146 Appendix B Cathodic Protection of Steel in Soil 150 Appendix C Corrosion of Steel in Soil 153 Appendix D Attenuation Equations 160 Index 163 vi Preface to Third Edition A pipe line buried in the earth represents a challenge. It is made of steel—a strong, but chemically unstable, material—and is placed in an environment which is nonuniform, nonprotective, and nonyielding. It is the duty of the corrosion engineer to study the properties of this system to ensure that the pipe line will not deteriorate. In 1955, when I was first working on cathodic protection for pipe lines in Saudi Arabia, the first edition of this book by Marshall Parker was just a year old. Fortunately, the company library contained Mr. Parker's book. I found its simplicity and directness preferable in approaching a complex subject. During the 30 years since its publication, generations of pipe line engineers and technicians have used this book as their first exposure to corrosion control. Many books on the subject have been published since 1954, but the Parker book is still the best introduction to the fundamentals. New technology has been developed, yet the principles of cathodic protection are still the same. The result is that we have more sophisticated instruments to use, but the measurements have not changed. Consequently, I have retained the still-valid material of the original Marshall text and made changes only when better and shorter methods are available. The first task of the pipe line corrosion engineer is to study the properties of the earthen environment. First, we shall learn how to measure the resistivity of the soil as a preparation for further work. In the second
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