Page 491 - Corrosion Engineering Principles and Practice

458 C h a p t e r 1 1 M a t e r i a l s S e l e c t i o n , Te s t i n g , a n d D e s i g n C o n s i d e r a t i o n s 459

FIGURE 11.20 Lamppost galvanized steel base with a gap over the concrete
to prevent crevice corrosion and pack rust.

Crowned pads for flat bottomed tanks will encourage free drain-
age of contents, particularly where a sump is provided. Crowning
also encourages free drainage of liquids from under the tank floor
under variations of hydrostatic head, which can pull corrosive liq-
uids under the tank. Use of pads slightly smaller in diameter than the
tank base will reduce the danger of moisture and chemicals being

Metal

(a) (b)

FIGURE 11.21 (a) Support pad protects horizontal tank from concrete
saddle, (b) better design: metal saddle with support pad (adapted from [18]).