Cathodic Protection

Cathodic protection effectively protects underground or submerged metallic structures through the use of a negative potential applied by an external source to the structure. Commonly, once the structure has been made sufficiently negative, environmental corrosion (soil or moisture) is resisted. The method is typically applied to iron or steel structures such as underground pipelines, storage tanks, the interior of water storage tanks, ocean pilings, and electrical transmission towers. Buried steel structures will revert back to their natural state as an iron oxide without proper intervention.

Image above, MATCO's Corrosion Department Manager, Geoff Rhodes, preperaing a hugh graphite anode that will provide protection from corrosion to a subgrade tunnel located underneath the Chesapeake Bay.  This form of corrosion protection, cathodic protection, is commonly used by many different industries including the electric power utilities, gas and pipeline, and water treatment systems.  MATCO's engineers are experts in all aspects of cathodic protection including design, installation, monitoring and troubleshooting.

MATCO has obtained a position of considerable prominence in the cathodic-protection field. As evidence of that, MATCO was hired to provide the entire gamut of CP services for the major liquefied-natural-gas (LNG) terminal in the United States where LNG from Algeria and other offshore sources in unloaded. The facility includes a mile-long submarine steel tunnel in which the pipelines and service utilities are located, all of the mooring pilings, the underground pipelines in the tanks farm on shore and other ancillary facilities.

Stray Current Corrosion

Where a protected structure, or the anode(s) or groundbed(s), lies near to other buried or immersed metallic structures that are not fully insulated from earth, the latter(secondary strucures may , at certain points , pick up a portion of protection current due to potential gradients in the soil or water and return it to earth at others. The secondary strucures may corrode at these latter points. The effect is described as stray current corrosion. There are two types of stray current corrosion: (1)Dynamic Stray Current and (2) static stray currents. Dynamic stray currents fluctuate while static stray currents do not exhibit fluctuation with time(static and continous). It should be noted that when stray current corrosion is detected, time is of the essence and failure(leakage) can occur in rather short time. The corrosion engineer needs to identify pick up and discharge stray current areas immediately. These locations can be determined by close interval survey and current interruption and recording the potentials by aata logger or other type of recorders. It should be noted that the current will alwaystake the path of least resistance and should always return to tis source. It is important to meet with different parties involved to determine the criterion that will be utilized to test , evaluate and mitigate any stray current (corrosion) that may be be identified. MATCO's certifed cathodic protection specilists will provide testing procedures and and acceptance criteria and resolution of stray current and interference problems that you may experience in your underground/water facilites.

On a more routine basis, MATCO provides CP services for systems from ones as small as an individual gasoline station tank system to major pipelines of many kinds. Contact us to find out how we can help to solve your CP problems.

EXAMPLES OF SOME PAST UNDERGROUND CORROSION ENGINEERING PROJECTS

• Field and laboratory evaluations of failed (blistered) fusion bonded epoxy (FBE) coated gas transmission pipe line, including soil corrosivity determination, coating analysis, blister fluid extraction and analysis, interpretation of close interval survey data, root-cause determination and recommendation.

• Soil resistivity surveys in support of the construction of a new AC power transmission line. The locations and right-of-way of the towers was selected with consideration given to the soil resistivity as related to grounding requirements.

• Forensic analysis to determine root cause of catastrophic gas line failures; explosion, corrosion, mechanical failure….

• Design and installation of internal galvanic cathodic protection systems for waste water treatment tank farms.

• Troubleshooting and remediation of coated steel production lines exhibiting through wall perforations only a few months after commissioning.

• Evaluation of installed cathodic protection system on newly commissioned coated steel production lines.

• Evaluation and remediation of cathodic protection system operating on a 25 mile long 12 inch diameter coated steel river water pipeline for coal washing.

• DC stray current and stray current  mitigation to abate damage on coated steel pipe replaced after less than one year of being commissioned.

• Design and installation of galvanic cathodic protection system for process piping at a refined petroleum products depot.

• Design and installation of galvanic cathodic protection systems for diesel fuel emergency fuel piping and storage tanks for hospitals and municipalities.

• Annual evaluations of impressed current and galvanic cathodic protection systems on gathering and distribution fuel gas lines, jet fuel transmission lines and service station gas/diesel fuel storage tanks.

• Cathodic protection system specifications for design phase of a 36 inch diameter ductile iron river-water pumping station and feasibility study for a new coking facility having over 4 miles of underground water, air and fuel gal lines.

• Inspection, troubleshooting and remediation of cathodic protection systems operative at a 260 MW cogeneration plant.

• Stray current dection and troubleshooting of cathodic protection systems operative at gas stations

Training and Education

To promote better understanding of cathodic protection and materials performance in different types of environments, MATCO offers many different training and educational seminars.  Seminars can be arranged to be held onsite or at our location.  MATCO has provided many seminars over the year and participitated in short courses for clients and associations, such as:  Appalachian Underground Corrosion Short Course (West Virginia); NASA Kennedy Space Center, IBM facilities (New York); Marco Energy Systems (West Virginia); National Association of Corrosion Engineers (NACE, Pittsburgh Chapter); and ASM International (Wisconsin and Pittsburgh).  If you would like more information, please contact Dr. Zee ( This e-mail address is being protected from spambots. You need JavaScript enabled to view it ) or Debra Riley ( This e-mail address is being protected from spambots. You need JavaScript enabled to view it ) or at MATCO's headquarters in Pittsburgh (412-788-1263).

Course Outline for Cathodic Protection

1. Essential Background Review
   Basic Electricity for CP
   Corrosion as an Electrochemical Reaction
   Types of Corrosion
2. Control of Corrosion
   Coatings
3. Cathodic Protection
   Insulated Joints
   Bonds
4. Measurement of CP Circuits
   Potential
   Resistance
   Current
5. CP Potential Measurement and Criteria
   Reference Cells
   Survey Methods and Analysis
   Criteria for Cathodic Protection
6. Galvanic (Sacrificial) CP Systems
   Materials and Types
   Installation Procedures
   Test Points
7. Impressed Current CP Systems
   Materials and Types
   Rectifiers
   Installation Procedures
   Test Points
8. Stray Current
   Dynamic Interference
   Static Interference
   Examples and Mitigation Measures
9. Records, Maintenance and Troubleshooting
   System Information and Inspection Records
   Routine Maintenance Schedules
   Troubleshooting Basics
10. Introduction to CP Design and Materials
    Basic concepts for CP system design
11. Examples, Experiments and Practical Problem Solving
12. Cathodic Protection Of Stainless Steels, Copper Alloys: Protection Criteria and Application

The instructors include NACE Certified Cathodic Protection/Corrosion/Coating Instructors, professional engineers, material scientists, and coating/materials selection/design specialists.

MATCO's Technical Notes on Cathodic Protection and Coatings

Cathodic Protection, by Dr. Zee, Dr. Gibbon, Geoff Rhodes and Dr. George Bayer, Internally published by MATCO.

Failure Analysis of Coatings, by Dr. George T. Bayer and Dr. Mehrooz Zamanzadeh, internall published by MATCO.

A Re-Examination of Failure Analysis, by Dr. Mehrooz Zamanzadeh, Dr. Donald Gibbon, and Edward Larkin, internally published by MATCO.

MATCO Provides Complete Corrosion Control Systems & Failure Analysis

Experienced PE, PhD Scientists, NACE Certified in Corrosion, Coating, Design, Materials Selection & Cathodic Protection Specialists who will solve your corrosion problems at both initial design stages and in service. We offer the most advanced forms of corrosion and materials engineering available, custom designed based on a review of the corrosion risk.

• Corrosion Engineering and Cathodic Protection of Underground Pipe Lines, Tanks, Production /Transmission Facilities: (a) Underground (b) Above Ground (c) Marine Environments
• Corrosion Evaluation, life expectancy determination
• Corrosion mapping, detection of "Hot Spots", cathodic protection of reinforced concrete structures
• Explosions/Fire Investigation forensic engineering
• Electrochemical EIS , DC and AC Testing - Determination of cathodic protection criteria for non-ferrous alloys and stainless steels
• On-site Evaluation of tanks and corrosion mitigation by protective coatings and internal or external Cathodic Protection
• Corrosivity determination of soil, water and determination of corrosion mitigation techniques
• On-site coating evaluation and selection of coatings for specific corrosive environments by EIS technique

Corrosion Group

Corrosion team is comprised of certified and experienced personnel from a variety of technical disciplines including: corrosion engineering, cathodic protection, coating/paint, inspection, chemistry, metallurgy, and materials science.  We also have a vast array of laboratory and field testing equipment. All of MATCO's testing equipment is calibrated on a routine basis in accordance with both national and international standards, and is ready to be put to use at a moment's notice.

Our team of NACE Certified Corrosion/Materials Selection/ Design/Coating/Cathodic Protection  Specialists (*) includes:

Dr. M. Zee(*)                                           Mr. Geoff Rhodes (*)

Dr. George Bayer                                    Ms. Debra Riley (*)

Mr. Ed Larkin                                          Dr. Kasraie, PE

Ms. Heather Groll (*)                               Dr. Bavarian

An illustrated formal report documents the results of the investigation. If necessary, MATCO personnel can usually be on site almost immediately when requested during emergency situations.