UFC 3-570-06
JANUARY 31 2003
components of the soil. This can occur in any soil that is a mixture of materials from
microscopic to substantially sized components. The area(s) with the higher potential
becomes the anode in this electrochemical corrosion cell. This is most severe when a
pipeline or tank is placed in an electrolyte with components that cause large potential
differences or where there are small anodic areas and large cathodic areas.
Figure 2-6. Concentration Cell Caused by Non-Homogeneous Soil
Cathodic Area on Tank
Dry Soil
Anodic Areas on Tank
Current Flow in the Earth
Reference Electrode
2-2.2.5
Concrete/Soil Interface. Pipelines or tanks that are in contact with cement
and exposed to another electrolyte exhibit different potentials in each area. The area
not in contact with cement becomes the anode in this electrochemical corrosion cell. A
pipeline or tank that is in contact with concrete and soil (or water) may be a very severe
corrosion cell, because of the high potential difference of the metal in the two different
electrolytes.
2-9
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