Page 472 - Corrosion Engineering Principles and Practice

438 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 439

FIGURE 11.7 Lamellar corrosion exfoliation of an aluminum alloy (A97075).
(Courtesy of Kingston Technical Software)

typical of wrought aluminum alloys where corrosion products
building up along these grain boundaries exert pressure between the
grains and the end result is a lifting or leafing effect (Fig. 11.7). The
damage often initiates at end grains encountered in machined edges,
holes, or grooves and can subsequently progress through an entire
section. Figure 11.8 shows how a fraction of material is often sacrificed
to alleviate the impact on the susceptibility to corrosion cracking of
the short transverse sections of a component.

Component
shape Grain flow

(a) (b)
FIGURE 11.8 Machining for neutralizing the effects of grain flow on corrosion
resistance: (a) saving on material and loosing on lifetime, and (b) loosing on
material for increased lifetime.