Electrical Design - Cathodic Protection Part I

Basic Concepts and Fundamentals

Bijan Ghayour, P.E.

Course Outline

This 12-hour course provides detailed information on the basic concepts and fundamentals of the cathodic protection systems, including an understanding of the cathodic protection concepts, cathodic protection system design principals, differences between impressed current and sacrificial anode systems, corrosivity of soils on steel based materials, and provides guidelines and examples for designing cathodic protection systems for underground and above ground structures.

Cathodic protection is an electromechanical method used to prevent or control corrosion of buried or submerged metallic structures. Cathodic protection 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 cathodic protection system is installed and adjusted to provide adequate protection, current and potentials should remain relatively stable; changes in currents or potentials indicate the presence of a problem.

This course offers recommendations and practical guidelines for understanding the fundamentals, and basic concepts; and for the proper and economical design of cathodic protection systems for variety of applications.

Part II of this course, covered in PDH course number E-223, provides detailed information on the installation and construction practices, system checkout and initial adjustments, maintenance of cathodic protection systems, and economic analysis.

The course materials are based entirely on the military handbook MIL-HDBK-1004/10 of Department of the Army: Electrical Engineering - Cathodic Protection.

This course includes a multiple-choice quiz at the end, which is designed to enhance the understanding of course materials.

Learning Objective

The purpose of this course is to provide the basic understanding and fundamentals of the cathodic protection systems.

At the conclusion of the course the student will be familiar with the:

• Cathodic Protection Concepts;
• Corrosion as an electrochemical process;
• The electrochemical cell;
• Components of electrochemical cell;
• Potentials required for cathodic protection;
• Practical application of cathodic protection;
• Functional requirements of cathodic protection system;
• Impressed current system;
• Sacrificial anode system;
• Anode materials;
• Connection to structure;
• Direct current power source;
• Criteria for cathodic protection including criteria for steel, aluminum, copper, lead, and dissimilar metal structures;
• Failure rate analysis;
• Consequences of under/over protection;
• Coating disbondment;
• Hydrogen embrittlement;
• General design procedures;
• Site surveys;
• Water analysis;
• Soil characteristics;
• Current requirements;
• Total resistance determination;
• Voltage and rectifier determination;
• Location of other structures in the area;
• Detection and control of interferences;
• Bonding for electrical safety;
• Advantages of impressed current system;
• Impressed current cathodic protection system design procedures;
• Basic equations;
• Simplified expressions for common situations;
• Effects of backfill;
• Selection of power supply type;
• Anodes for impressed current system;
• Test stations;
• Advantages of sacrificial anode system;
• Sacrificial anode cathodic protection system design procedures;
• Determination of number of anodes required;
• Determination of anode life;
• Sacrificial anode materials; and
• Cathodic protection system design examples:
  - Elevated steel water tank
  - Steel gas main
  - Gas distribution system
  - Underground steel storage tank
  - Heating distribution system
  - Aircraft multiple hydrant refueling system
  - Steel sheet piling in sea water (Galvanic anode)
  - Steel sheet piling in sea water (Impressed current)
  - Steel H piling in sea water

Intended Audience

This course is intended for electrical engineers and maintenance personnel involved in the design, service, maintenance, and upgrade of cathodic protection systems.

Benefit to Attendees

This course is intended for use in the design of cathodic protection systems for the mitigation of corrosion of buried or submerged metallic structures.

Design of cathodic protection systems is somewhat different than design of other electrical or mechanical systems because it must be based upon local environmental conditions such as soil resistivity and moisture content.

This course presents criteria for cathodic protection, methodologies for the determination of required environmental conditions, methodologies for design of cathodic protection systems, examples of typical systems and design calculations, recommended initial system checkout procedures, and system maintenance requirements.

After the completion of the course the attendees will be able to evaluate the existing conditions at a specific site and determine the need for a cathodic protection system. The attendees will also be able to recommend an appropriate system based on the various field conditions and proceed with the design of a functional and economic cathodic protection system for different corrosion protection purposes.

Course Introduction

In most industrial, naval, and utility projects the corrosion of buried or submerged metallic structures will result in various kinds of failures resulting in loss of services and production.

This course provides detailed information on the basic concepts and fundamentals of the cathodic protection systems, including an understanding of the cathodic protection concepts, cathodic protection system design principals, differences between impressed current and sacrificial anode systems, corrosivity of soils on steel based materials, and provides guidelines and examples for designing cathodic protection systems for underground and above ground structures.

By proper selection and the design of an appropriate cathodic protection system, the life of buried or submerged metallic structures can be extended many folds, resulting in more reliable systems and substantial saving in equipment replacement costs.

Part II of this course, covered in PDH course number E-223, provides detailed information on the installation and construction practices, system checkout and initial adjustments, maintenance of cathodic protection systems, and economic analysis.

Course Content

This course contains the basic principals and fundamentals of different cathodic protection systems. This course also offer specific example for the design and evaluation of the new or existing corrosion protection systems. You are required to study sections 1 through 10 and Appendix A of the military handbook MIL-HDBK-1004/10 of Department of the Army USA, ELECTRICAL ENGINEERING CATHODIC PROTECTION:

ELECTRICAL ENGINEERING CATHODIC PROTECTION (PDF 2.7MB)

(For an electronic copy of MIL-HDBK-1004/10 go to http://www.wbdg.org/ccb/DOD/UFC/ufc_3_570_02n.pdf)

Please click on the above underlined hypertext to view, download or print the document for your study. Because of the large file size, we recommend that you first save the file to your computer by right clicking the mouse and choosing "Save Target As ...", and then open the file in Adobe Acrobat Reader. If you still experience any difficulty in downloading or opening this file, you may need to close some applications or reboot your computer to free up some memory.

The following contains the outline of the FIST 4-1B of Department of Interior, Bureau of reclamation:

ELECTRICAL ENGINEERING CATHODIC PROTECTION

Table of Contents

Section 1- Introduction
Section 2- cathodic Protection Concepts
Section 3- Criteria for Cathodic Protection
Section 4- Cathodic Protection System Design Principals
Section 5- Precautions for Cathodic Protection System Design
Section 6- Impressed Current System
Section 7- Sacrificial Anode System Design
Section 8- Typical Cathodic Protection
Section 9- Cathodic Protection System Design Examples
Section 10- Installation and Construction Practices
Section 11- System Checkout and Initial Adjustments
Section 12- Maintaining Cathodic Protection
Section 13- Economic Analysis
Section 14- Corrosion Coordination Committee Participation

Appendix A- Underground Corrosion Survey Checklist
Appendix B- Economic Life Guidelines
Appendix C- Project Year Discount Factors
Appendix D- Present Value Formulae
Appendix E- DOT Regulations

Quiz

Once you finish studying the above course content, you need to take a quiz to obtain the PDH credits.

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DISCLAIMER: The materials contained in the online course are not intended as a representation or warranty on the part of PDH Center or any other person/organization named herein. The materials are for general information only. They are not a substitute for competent professional advice. Application of this information to a specific project should be reviewed by a registered architect and/or professional engineer/surveyor. Anyone making use of the information set forth herein does so at their own risk and assumes any and all resulting liability arising therefrom.

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