Figure 4-9.Pitting of an aluminum wing assembly.
Figure 4-10.Concentration cell corrosion.
faulty design or improper maintenance practices. You
To keep these metals from coming in direct
can usually recognize it by the presence of a buildup
contact with each other, aircraft and support
of corrosion at the joint between the metals. For
equipment manufacturers use a variety of separating
example, aluminum and steel materials riveted
materials. Such materials include plastic tape, sealant,
together in an aircraft wing form a galvanic couple if
primer, washers. and lubricants. These materials keep
moisture or contamination is present. When aluminum
corrosion to a minimum. These separating materials
pieces are attached with steel bolts or screws, galvanic
must remain intact and be replaced, restored. or
corrosion can occur around the fasteners (fig. 4-12).
repaired as needed.