Page 334 - Challenges in Corrosion Costs Causes Consequences and Control(2015)

312 CORROSION CONTROL AND PREVENTION

TABLE 4.51 Annual Coating Maintenance of Navy Surface Ships
Activity Man-Years Per Slip
Topside and freeboard (enamel, silicone alkyd) 9.0
Flight decks and topside decks (nonskid) 4.0
Bilges/wet space corrosion 4.5
Machinery space/passageways (enamel, silicone alkyd) 2.25
Interior bulkheads and decks (chlorinated alkyd) 3.00
Superstructure, catwalks, mixing/fan room corrosion (epoxy) 3.25
Total 26.00

corrosion, repair maintenance because of corrosion, washing sealant application and
removal, and all coating application and removal.
Comparison of 1997 fleet costs with 1990 fleet costs showed the effect of aging
on weapon system costs. The corrosion problems with A-10, C-130, and F-16 have
been resolved. The cost of corrosion maintenance of B-1 and E-3 fleets increased.
A severe corrosion problem occurs in fuselage joints, where the voluminous cor-
rosion products at the contact or faying surfaces of the lap joint cause deformation
of the skin. Pillowing phenomenon occurs in lap joints. Because of the stress fatigue
and stress corrosion, cracks can nucleate near the fastener holes, jeopardizing the
structural integrity of the fuselage. Other corrosion problems on KC-135 aircraft are
dissimilar metal corrosion, lap joint corrosion on the 7178 upper wing skin, lap joint
corrosion on the 7075-T6 fuselage crown section, and SCC of the 7075-T6 forged
frame sections.
As a result of the numerous corrosion problems of the KC-135, the Air Force in
the United States expended considerable effort to develop methods to control corro-
sion of the KC-135 ranging from characterizing the type and extent of corrosion to
developing new nondestructive techniques, to developing methods to slow down cor-
rosion with corrosion preventative compounds (CPCs), and to developing predictive
models.
Severe corrosion occurred in aluminum alloy components of the KC-135
Stratotanker aircraft. Corrosion is because of low utilization, and the majority of
the time is spent on the ground being exposed to corrosive atmospheric environ-
ments. The KC-13 aircraft was built with aluminum alloys 2024-T3 and T-4, and
7075-T6 and 7178-T6, which are all susceptible to corrosion and SCC. The original
construction was without any sealant in the lap joints and fuselage skins that had
spot-welded doublers attached to them. The upper wing skins that are made of highly
corrosion-susceptible aluminum alloy 7178 were attached with high-strength steel
fasteners, causing dissimilar metal corrosion in certain areas.

4.35 PREVENTIVE STRATEGIES

The aim of preventive strategies is to use the opportunities to improve corrosion con-
trol in all economic sectors, which will result in increased integrity, durability, and