Why is the corrosion protection system for concrete pressure pipe so effective?
Carbon steel embedded in portland cement concrete or mortar undergoes a unique chemical change at its surface. The very high pH of the concrete or mortar (in the range of 12.5 to 13.0) causes a hard, thin oxide layer to form on the steel surface passivating it. This passivation prevents corrosion from occurring. Small cracks in the mortar or concrete do not affect this type of corrosion protection. Electrochemical corrosion protection of this type is far superior to barrier-type coatings such as paints or membranes—which are never pinhole-free.
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