Page 222 - 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

FIGURE 6.46 Stress corrosion crack in a bronze monument caused by buildup
of rust around an iron rod. (Courtesy of Kingston Technical Software)

mating surfaces and, because they occupy so much more volume
than the metal from which they are produced, generate sufficient
stresses to cause SCC. In the example shown in Fig. 6.46, moisture
working down the iron rod in combination with the galvanic corrosion
due to the contact with the bronze support caused enough rust build-
up to generate high stresses and induce SCC.

6.5.1 Stress Corrosion Cracking
It is not uncommon for growing cracks to be considered acceptable
(Fig. 6.47) so long as they are substantially less than a critical crack
size [Fig. 6.47(a) and Eq. (6.11)] and can be repaired at the next