Page 268 - Corrosion Engineering Principles and Practice

242 C h a p t e r 7 C o r r o s i o n F a i l u r e s , F a c t o r s , a n d C e l l s 243

FIGURE 7.33 Photograph of the Boeing 737 operated by Aloha Airlines that lost
a major portion of the upper fuselage in 1988.

The following example has baffled the airline industry through a
few investigations. In this case, the deformation due to the corrosion
of aluminum in lap joints of commercial airlines was accompanied by
a bulging (pillowing) between rivets, due to the increased volume of
the corrosion products over the original material. This problem was
said to be the primary cause of the Aloha incident (Fig. 7.33) in which
a 19-year-old Boeing 737, operated by Aloha airlines, lost a major
portion of the upper fuselage in full flight at 7300 m [19]. The
“pillowing” process in which the faying surfaces are forced apart is
schematically illustrated in Fig. 7.34.
The prevalent corrosion product in corroded fuselage joints was
found to be hydrated alumina [Al(OH) ], with a particularly high
3
volume expansion relative to aluminum as shown in Fig. 7.35 [20].

Voluminous corrosion products
generate stresses and
lead to “pillowing”

Ingress of corrosive
electrolyte

FIGURE 7.34 Schematic description of the “pillowing” of lap splices.