Specialty Tanks

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Glossary

Class A Certification

Pitting on a Tank

1. Galvanic

(two-metal)

2. Crevice

Occurs in shielded areas of metal surfaces, such as local deposits of sand, dirt, etc. that create stagnant conditions of a liquid in contact with the metal.

3. Pitting

Common to the outside of USTs.

4. Intergranular

Usually due to the improper welding of stainless steels.

5. Selective Leaching

This is the selective corrosion of specific alloying constituents from an alloy (e.g. carbon from carbon steel).

6. Erosion

This is accelerated corrosion due to the presence of abrasive materials.

7. Stress

This is accelerated corrosion due to the presence of tensile stress upon a metal.

5.1.3.2   Localized Attack

         This type of corrosion is divided into seven sub-types (see the list below)

         It is common to the outside of USTs and along the bottom inside of tanks typically covered by water and/or particulates

         It is very difficult to predict

         It causes unexpected failures

         It accounts for roughly 70% of all failures due to corrosion

Seven Types of Localized Attack