What matters most
Wenner soil-resistivity testing can map electrical conditions along a proposed or existing buried-utility route and support corrosion assessment, material selection, failure investigation, or cathodic-protection design input. Interpretation must also consider the material, coating, joints, isolation, chemistry, moisture, redox, stray current, geometry, and operating history.
Key takeaways
- Tie stations to alignment, depth, crossings, drainage, and observed failures.
- Use resistivity as one corrosion input—not a service-life calculator.
- Pair field surveys with focused chemistry or soil-box work when needed.
- Cathodic-protection system design remains a separate specialty scope.
Place stations where the exposure can change
Consider soil and geology transitions, wetlands, irrigation, road and rail crossings, utility congestion, casings, drainage, fill, shallow groundwater, industrial areas, known leaks or failures, and material transitions.
For existing assets, align stations with pipeline stationing and preserve offset and orientation. Do not drive electrodes without utility clearance and owner approval.
Resistivity does not equal corrosion rate
Lower resistivity can support larger corrosion currents, but metal loss depends on electrochemical reactions, coating-defect area, oxygen or redox, salts, pH, sulfides, temperature, dissimilar-metal contact, stray current, and polarization.
Use the field data to identify exposure differences or supply a qualified specialist with current-flow information. Avoid universal tables that convert one resistivity value to years of life.
Combine field and sample data intentionally
Representative soil samples can provide pH, chlorides, sulfates, redox, sulfides, moisture, and controlled soil-box resistivity. Field Wenner measurements preserve the route-scale current paths and layering.
The investigation report should explain what each method represents and connect conclusions to the actual pipe, coating, installation, history, and observed damage.
Calicore performs field Wenner surveys, soil corrosivity testing, site assessments, and failure investigations. Cathodic-protection system design is not represented as part of the standard service.
This page provides general educational information, not a grounding-system design, cathodic-protection design, installed-system acceptance test, or parcel-wide resistivity conclusion. A Wenner result is apparent soil electrical resistivity for the documented array, spacing, location, orientation, and field condition. The responsible grounding or corrosion engineer must evaluate the complete dataset, earth model, asset geometry, governing documents, and uncertainty.
Frequently asked
Questions about this topic
Does low soil resistivity mean a pipe will fail?+
No. It is one factor affecting current flow. Failure also depends on the asset, coating, chemistry, electrical conditions, geometry, installation, and time.
Can a Wenner survey locate a coating holiday?+
No. It characterizes ground response. Coating defects and CP performance use different field techniques.
Should samples be collected during the survey?+
They can add value when chemistry, moisture, or controlled soil-box data is needed. Define sample locations and preservation before mobilization.
Primary references and further reading
- ASTM International — ASTM G57-20 Official record for the Wenner four-electrode field and four-electrode soil-box method.
- ASTM International — ASTM G187-23 Official record for two-electrode soil-box resistivity testing of removed samples.
- Soil Tests Laboratory — Wenner Four-Pin Testing Calicore Engineering’s testing division and field-service information.