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DIFFERENTIAL AERATION AND STAINLESS STEEL

Of the many different types of corrosion, the most common to underground piping
systems is concentration cell corrosion. Also called "differential aeration corrosion" and "crevice corrosion", it defines corrosion which has the tendency to build up more rapidly in cracks and crevices or between overlapping layers.

This occurs when one part of a metal is exposed to a different air or oxygen concentra- tion than the other parts.

This causes a difference in potential between differently aerated areas. Areas on a metal surface where the oxygen concentration is low are anodic and corrosion prone.

Stainless steel is susceptible to crevice corrosion depending upon the shape into which it is fabricated and to the degree of crevices or inside corners formed during its fabrication.

Even though stainless steel is resistant to corrosion due to an oxide coating, any disturbance or damage to this coating exposes the metal underneath.

This exposed area is then vulnerable to corrosive attack. The fabrication process can damage this oxide coating.