Page 169 - Challenges in Corrosion Costs Causes Consequences and Control(2015)

HAZARDOUS MATERIALS STORAGE 147

Figure 3.15 Oil storage tank farm (7).

Atmospheric
corrosion
Wind girder

Vapor space corrosion

Crevice
Product side corrosion corrosion

Aqueous phase corrosion
Bottom corrosion

Tank bottom underside corrosion
Figure 3.16 Internal and external corrosion modes of oil tanks (7).

and pitting corrosion damage. In addition, MIC can be a problem under anaerobic
conditions. Internal corrosion problems are exacerbated by the stresses and flexing
that the metal undergoes during fluctuations in product levels.

3.10.1.2 External Corrosion Atmospheric corrosion of the external wall and the
roof is a result of general corrosion and crevice corrosion damage. Aboveground tanks
suffer from external corrosion as a result of the tank bottom sitting on a grade with
a variety of corrosive padding materials or on a back-filled concrete ring wall. Both
types of tank bottom supports can cause external pitting of the bottom steel plate.
Small aboveground tanks suffer from external atmospheric corrosion, but to a lesser
degree because they can be supported off the ground, and the rounded surface mini-
mizes crevice corrosion problems.