Soil Testing

MATCO Services has years of experience in all aspects of on-site and laboratory inspection and assessment of soil corrosivity. Our team includes Ph.D.s, registered professional engineers, and certified inspectors from a variety of technical disciplines, including corrosion engineering, coating inspection, chemistry, metallurgy and materials science.

Soil Resistivity Measurements

One method of measuring resistivity is that described in AASHTO T 288, Determining Minimum Laboratory Soil Resistivity, which was developed from a California Department of Transportation procedure sanctioned by the Federal Highway Administration (FHWA) for evaluating mechanically stabilized earth (MSE) backfill. The American Society for Testing and Materials (ASTM) has a different procedure that is currently in the process of revision. The method described in ASTM G57, Standard Test Method for Field Measurement of Soil Resistivity Using the Wenner Four-Electrode Method, is replaced by a two-part standard: Part A will cover the four-electrode method for in situ field measurements, and Part B will cover the use of a soil box for laboratory and field-test measurements. In both methods, the measured resistivity is dependent on the electrical frequency of the test apparatus, but in neither case has the form of the dependency been established exactly. We also have a comprehensive array of laboratory and field testing equipment, all calibrated on a routine basis in accordance with both national and international standards. This team is ready to be put to use at a moment's notice.

Soil Corrosion

Corrosion on underground facilities is directly related to the soil conditions present for the unique location of a given structure, as well as to the materials of manufacturing and the quality of these materials. Poles and towers in submerged conditions are subject to a greater risk of corrosion because of the continuous presence of moisture – the electrolyte necessary to have the electrochemical corrosion reaction proceed. The specific chemical composition, resistivity and redox potential of the electrolyte in the soil will determine the relative corrosivity or risk of corrosion.

In addition to the soil characteristics, it is useful to measure the electrochemical potential of the structure in the electrolyte. This is done using methodologies developed by the underground pipeline industry and recognized by NACE International and other professional societies and regulatory organizations. The structure-to-soil potential of a buried asset can be related to the present state of corrosion, with less electronegative values of potential indicated an increasing likelihood of active corrosion. By using sacrificial (galvanic) cathodic protection, corrosion can be mitigated by shifting the structure-to-soil potential to more electronegative values where the corrosion reactions are not favored thermodynamically. The amount of galvanic current required to obtain acceptable levels of cathodic protection can be calculated.

A site investigation includes partial excavation for visual assessment of the underground structure. The visual observation complements the non-invasive structure-to-soil potential evaluation and, in the instances of active corrosion, allows direct assessment of the state of corrosion and material loss. It also allows for visual observation of mechanical damage (bent components) and the condition of protective coatings at and below the ground line. If sufficient material loss has occurred to compromise the design strength of the structure, replacement of the components may be required.

The first steps in a site investigation for transmission towers include recording the tower identification, type, and GPS location. Leg orientation will be confirmed and recorded before performing any inspection evaluations. The immediate area surrounding the structure must also be examined and documented to look for other structures or buried assets which may influence the evaluations which are to follow.

Soil resistivity will first be measured and recorded as specified at each leg of the structure before any soil is disturbed. Structure-to-soil potentials will also be profiled at each leg before soil disturbance. The profile length should equal the reported depth of the sub-surface structure. To the extent possible the profile should proceed radially away from the leg corner in order to minimize potential gradient influence from the adjacent legs.

As excavation proceeds, soil samples should be obtained from the near-surface and bottom of the excavation, or wherever different soil conditions are noted. Soil pH and redox potential should be measured on-site; samples will be procured for off-site analyses of sulfur and chloride content, with enough sample quantity retained for additional evaluations of pH, soil composition or soil resistivity per ASTM G 57 if required or requested at a later time.

Excavation of the buried structure to the required depth should be conducted. Dirt/rust removed should be removed from the structure by brushing and/or washing. Visual assessment may be complemented by holiday testing on coated structures; paint and zinc coating thickness measurements may both be required.

Method for Determination of Soil Corrosivity

The following will help you establishing a basis for estimating the probability of corrosion of buried facilities whose external surfaces are in contact with soil. However, the probability of corrosion of these items is not only governed by the corrosiveness of the soil and the properties of the steel, but also by their design, their size and by external electrochemical effects (i.e. stray currents, etc.). Since these parameters cannot always be described with adequate accuracy, the likely corrosion behavior can only be estimated.

Such estimates (like the one below), besides providing information on the type and extent of the expected corrosion, also serve as a basis for deciding which protective measures may, or must, be taken.

Below, different soil characteristics will be evaluated and each of them will get a certain rating. The sum of those ratings is a measure for the overall soil corrosivity.The parameters rated include:

Following this, the rating numbers R1 through R12 should be added together. In the assessment of the different parameters 1 through 12, only one rating, namely the most negative one, shall be used in each case. The corrosiveness of the soil is then given below.

The MATCO team has experience working in many other diverse fields; from fracture mechanics, cathodic protection to paint inspection to failure analysis to remaining life determination. Some of our clients include Allegheny Energy, Valmont, California Edison, US Airways, First Energy and NY Power.

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. .

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.

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.

Training and Education

To promote better understanding of cathodic protection and materials performance in different types of soil environments, MATCO Services, Inc offers many different training and educational seminars.  Seminars can be arranged to be held onsite or at our location for a nominal fee which includes certifications.  Over the years, MATCO has provided many seminars and participated 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).  Currently, we are organizing two seminars: one on  Corrosion Engineering and one on Cathodic Protection/Coating for Pipe Line/Tank Corrosion Control.  Those interested in either of these seminars or future seminars should contact Dr. Zee at 800-221-9090.

Course Outline for Cathodic Protection

• Essential Background Review
Basic Electricity for CP
Corrosion as an Electrochemical Reaction
Types of Corrosion

• Control of Corrosion
Coatings
Cathodic Protection
Insulated Joints
Bonds

• Measurement of CP Circuits
Potential
Resistance
Current

• CP Potential Measurement and Criteria
Reference Cells
Survey Methods and Analysis
Criteria for Cathodic Protection

• Galvanic (Sacrificial) CP Systems
Materials and Types
Installation Procedures
Test Points

• Impressed Current CP Systems
Materials and Types
Rectifiers
Installation Procedures
Test Points

• Stray Current
Dynamic Interference
Static Interference
Examples and Mitigation Measures

• Records, Maintenance and Troubleshooting
System Information and Inspection Records
Routine Maintenance Schedules
Troubleshooting Basics

• Introduction to CP Design and Materials
Basic concepts for CP system design

• Examples, Experiments and Practical Problem Solving

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

Our team includes NACE Certified Corrosion / Cathodic Protection / Materials Selection / Design / Coating Specialists (*) and other materials experts includes:

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

Ms. Heather Groll (*)                                   Mr. Antonio DiNunno (*)

Dr. George Bayer                                        Mr. Sam Scheinman (*)

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 Services, Inc

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

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

MATCO Provides Complete Corrosion Control Systems & Failure Analysis

Experienced PE, PhD Scientists, NACE Certified in Corrosion, Coatings, Design, Materials Selection & Cathodic Protection Specialists who will solve your corrosion problems at both initial design stages and in service.

Corrosion Engineering and Cathodic Protection of Production/Transmission Facilities: (a) Underground (b) Above Ground (c) Marine Environments

• Corrosion evaluation, life expectancy determination and cathodic protection of electrical poles and transmission lattices
• 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