Page 221 - Corrosion Engineering Principles and Practice

196 C h a p t e r 6 R e c o g n i z i n g t h e F o r m s o f C o r r o s i o n 197

(a)

(b)
FIGURE 6.45 Axial or transgranular cracks filled with oxide or scale
(a) observed on the external surface of a pipeline. These cracks may
occur in association with pits and general corrosion (b). (Courtesy of
MACAW’s Pipeline Defects, published by Yellow Pencil Marketing Co.)

or more complex. Cooling from the high temperatures required may
also induce internal stresses because of nonuniform cooling. In fact,
very slow, controlled cooling is a prerequisite for effective stress relief.
Another source of stress may come from corrosion products from
general corrosion or other forms of corrosion may build up between