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Soil Corrosivity and Corrosion Rate Determination

Matergenics – Pittsburgh has created a specialized market in soil corrosivity,  corrosion risk assessment and identification of corrosive hot-spots for underground assets and infrastructure that is not considered by traditional Close Interval Surveys (CIS) and circumvent functioning cathodic protection (CP). Our dedicated soil lab has rapid turn-around times and is supported by a multidiscipline team of soil specialists,  NACE certified materials and corrosion engineers, CP design and installation specialists, coatings specialists, chemists, and and certified lab and field technicians. The combination of field and lab analysis provides essential data for geotechnical, asset management, site surveys, CP installations, and failure analysis.

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Field and Laboratory Soil Analysis Capability

Knowing the corrosion rate of a metallic material is critical to determine the remaining life of underground structures. It also helps to understand whether or not mitigation, coating or cathodic protection is required.

We at Matergenics are not only able to determine the corrosion, but we also have the expertise to provide you with corrosion rate and  a recommendation that is specific to your specific application.

Predictive models for pit growth and material loss have been developed for underground ferrous materials (Pipeline, Tanks, T&D and Galvanized Anchors) based on statistical analysis on collected data obtained from:

  •  Surveys of the condition of buried structures
  •  Scientific exposure of buried materials
  •  Sensor-based studies or monitoring of buried materials and coupons

Soil Chemistry and Corrosivity

In early studies, the NBS data were used to estimate corrosion performance parameters  for different soil types. Forty- seven (47) NBS soil sites were divided into 4 groups based on aeration level, ranging from well-aerated sands to poorly aerated tidal marshes.

From a practical point of view, it is desired to relate regression model parameters to measurable physiochemical properties of soils. To address this, different sets of coefficients and modified forms of the regression model are proposed by several researchers based on NBS data and other similar experiments. In Matergenics predictive  model a wide range of corrosion parameters are involved such as:

  • Sulfate Ion Content in Soil
  • Chloride Ion Content in Soil
  • Redox Potential
  • Moisture Content of Soil
  • pH of Soils
  • Instantaneous Corrosion Rate, C.Steel, Galvanized  Steel, Stainless Steel, Copper, Brass..
  • Soil Resistivity
  • Sulfide Ion
  • Carbonates and Bicarbonates
  • Buffering Capacity
  • Electrochemical Testing

Matergenics have reviewed, all available predictive models and the most relevant regression coefficients are used to predict the corrosion rate for the client’s assets in given soils based on the corrosion performance parameters (above data).

Predictive Models for Corrosion Penetration and Pitting

The following criteria are used for  the recommended predictive models :

  1. Validation against short term and long term corrosion data
  2. Dependency of model parameters to relevant physiochemical parameters

Using our unique algorithms developed by expert corrosion engineers, the soil around a buried metallic asset is assigned a soil corrosivity (SC) rating that is based on a number of parameters including soil resistivity, pH, chlorides, sulfates, properties,.. and linear resistance polarization corrosion data. These ratings identify high soil corrosivity areas where assets are located and, based on these ratings, decisions for inspection frequency, prioritization, and long term planning can be made with confidence. This approach is what distinguishes us from our competition.

Based on chemical analysis and  corrosion performance parameters of the soil we are able to predict the corrosion rate and pitting in the  given soil. Life expectancy and remaining life is predictable in corrosive soils by our predictive model that is based on field evaluations and laboratory testing of soil.

 

Predictive Model/Plots for Different Soil Environments

Our capabilities also  include materials testing, failure analysis, computer aided design of cathodic protection/installation, corrosion risk assessment of underground/aboveground assets and a soil testing laboratory that performs many thousands of soil corrosivity tests each year. What makes us different from other labs is our predictive model for material loss based on soil chemistry and corrosive properties. Our model is based on many thousands of field data and findings and predicts corrosion penetration with moderate to high certainty. We can implement our model for your specific site(s) and provide life or remaining life expectancy for your underground assets based on soil properties at your specific location for shallow and deep burial.

 Soil Testing 

Determination            Soil Corrosion                    Performance                       Parameters      Comments
Simple Soil Chemistry pH, Resistivity, Chlorides, Sulfate, Sulfide, Moisture, Redox Potential Based on ASTM Techniques
Corrosion rate based on LPR/ER for: Steel, Zinc, SS Cu in given soil Mils /year (mpy) Instantaneous Corrosion Rate Based on ASTM G96
MIC Study SRB, APB,… Total Bacteria, SRB, APB, IOB,..
Predictive Modeling Long Term Corrosion Behavior of the Asset and Corrosion Mitigation Recommendation Provides corrosion penetration as a function of time (long term,10, 20, 30, ..50 years)

 

Standard Soil Tests by Matergenics

    • AASHTO T290: Sulfate Ion Content in Soil
    • AASHTO T291: Chloride Ion Content in Soil
    • ASTM C1580: Sulfate Ion Content in Soil A
    • STM D1498: Redox Potential of Water A
    • STM D2216: Moisture Content of Soil
    • ASTM D2487: Soil Classification
    • ASTM D421: Dry Prep SOIL SAMPLES
    • ASTM D4318: Liquid Limit, Plastic Limit, Plastic Index of Soils
    • ASTM D422: Particle Size Analysis of Soils
    • ASTM D4972: pH of Soils
    • ASTM G102: Corrosion Rate
    • ASTM G51: pH of Soil for Corrosion
    • ASTM G57: Soil Resistivity
    • ASTM D4658: Sulfide Ion in Water
    • ASTM G162: Conducting and Evaluating Lab Soil Corrosion Tests
    • ASTM D512: Chloride Ion in Water
    • MIC Tests

In summary, we can determine soil chemistry, estimate soil corrosivity, quantify corrosion risk, predict the corrosion rate and life expectancy of given underground asset based on chemistry of a soil environment it is exposed to. Having this data will enable you to predict the remaining life and if you must  install cathodic protection system to maintain your assets.

GIS Corrosion Mapping and  Risk Assessment

The corrosion of steel structures poses a significant financial and structural problem for many utility companies. While corrosion could occur at numerous places on the structures, below ground corrosion is of particular concern. This type of corrosion cannot be seen in a normal visual inspection and can only be inspected by excavating around the structure’s foundation. If left unchecked, it could weaken the structure which could result in failure. The problem is that a Piping or T&D utility’s territory may cover thousands of square miles, and companies need a plan to maximize their limited resources to effectively manage their below ground corrosion issues. As such, an accurate and practical method to remotely predict and locate specific areas of high, moderate, and low corrosion risk is imperative to corrosion mitigation and planning. We can determine  the effect of physical and chemical properties of soil on the acceleration of corrosion in steel structures by GIS Corrosion Mapping.

MAPPING PROCEDURE

A soil corrosion risk assessment map is developed by combining relevant information from individual maps in a geographic information system (GIS). However, prior to the final results, all data layers are analyzed for errors and corrected accordingly. Such corrections include null value reassignment and projection changes. Data are then reclassified to a common scale before preforming a weighted analysis.

Soil pH and soil electrical conductivity are assigned the highest weighting factors, as they are considered the key parameters to define the corrosivity of a soil service environment for buried steel components. Other factors, including clay content, drainage class, soil texture, etc., represent below-grade time of wetness and were assigned weighting factors lower than those assigned to the chemical properties of soil.

The following maps are examples of  process to develop a corrosion risk assessment map.

 

 

GIS PH Mapping for Houston and Surrounding Counties

 

Soil Drainage for Houston Surrounding Counties

The Spatial Analysis Weighted Overlay tool in GIS is used to weight, combine, and compare all soil parameters. The largest weighting factors are assigned to soil pH and electrical conductivity layers, while the remaining layers are weighted according to their relative importance in estimating underground time of wetness. A soil corrosion risk assessment map is created based on these conditions and is presented below.

Final GIS Corrosion Map Considering all Corrosion Performance Parameters not just PH and Drainage

 

 

Matergenics – Soil Testing Brochure

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Team Matergenics Provides Corrosion Mitigation for under ground assets in corrosive soils:

Please see the following video:

https://youtu.be/9HvbMGbWs-U

We are here to help

We respond to all customers promptly by sending a technical proposal to address testing, investigation and the proposal costs. If we need more information, our engineers will contact you.We respond to all customers promptly by sending a technical proposal to address testing, investigation and the proposal costs. If we need more information, our engineers will contact you. Whether you are a large corporation or a small enterprise, we will provide you with the attention you need and deserve. In so doing, we hope to work with you for many years to come.

Please call Dr. Zee at 412-952-9441, Tara at 412-537-6239 or 412-788-1263 and let us know how we can assist you in your soil investigation. Alternatively, you can send your request to info@matergenics.com.

Looking forward to hearing from you!

Matergenics – Soil Testing Brochure 2

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