Soil resistivity as related to underground corrosion and cathodic protection

Corrosion and Cathodic Protection in Underground Piping Systems

THE GALVANIC CELL The major corrosion concern in the water works industry is “galvanic” corrosion. Galvanic corrosion takes place due to current flow in a “galvanic cell” which is defined as (1) two dissimilar metals, an anode and a cathode, (2) in electrical contact with each other and (3) a common electrolyte. A galvanic cell is produced when the pipeline components come in contact with the s...

Corrosion and Cathodic Protection Theory

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Coatings and Cathodic Protection for Underground Pipelines - What a Corrosion Engineer Should Know

Coatings control corrosion by providing a barrier against oxygen and water. Although coatings are extremely effective, all organic coatings are semi-permeable to O2 and water. The water permeability coefficient of fusion bonded epoxies, one of the best coating systems, is approximately 10 gms/mil/24 hours, but minimum concentration of oxygen and water that can start the corrosion process is 10 ...

Cathodic Corrosion Protection of earthburried Pipelines

Steel Grounding Design Guide and Application Notes

Based on the National Bureau of Standards [presently called The National Institute of Standards and Technology or “NIST”] statistical data on corrosion of steel, an equation is introduced to estimate the corrosion rate of underground steel. The variables include the major soil characteristics (parameters), namely: resistivity, pH value, moisture content and aeration. This formula, together with...