Page 332 - Challenges in Corrosion Costs Causes Consequences and Control(2015)

310 CORROSION CONTROL AND PREVENTION

Many of the components of the vehicle such as fasteners, handles, brackets, and
frame were made from 1010 carbon steel, which is prone to corrosion with ease.
These parts corroded on almost every HMMWV in service leading to extensive
repairs and maintenance. Vehicle parts such as the engine compartment, suspension,
and steering, body, underbody, and other miscellaneous parts such as welded seams,
fuel tank assemblies, nuts, bolts, fasteners, and frame suffered corrosion and the
percentage of vehicles affected was in the range of 13–76%.
Most of the corrosion problems in HMMWV vehicles could have been eliminated
by using galvanizing and coatings. Other problems could have been avoided by using
polymers and other alternate materials.
Much of the body of the HMMWV is made of aircraft grade aluminum while
the frame and doors are made of 1010 carbon steel. The whole vehicle is secured
with more than 2800 rivets, which gives high strength-to-weight ratio. Each rivet is a
preferential site for corrosion.
Electrodeposition of coatings assures complete coverage of the surface including
otherwise inaccessible areas. On the HMMWV, e-coating technology was not used
for coating application, and coating was applied by spraying.
Chemical agent-resistant coatings (CARC) consist of a surface cleaning, epoxy
primer, epoxy interior topcoat, and a polyurethane exterior top coat. The purpose of
this coating was to provide resistance to chemical penetration of the coating and to
aid in decontamination of the vehicle in case of chemical attack. Other purposes of
the coating were to provide corrosion protection as well as camouflage protection.
The CARC Paint System did not perform as well as expected (Table 4.50).
CARC coating is difficult to apply. It is also difficult to achieve the required thick-
ness levels. Field repair of CARC coating was found to be difficult. CARC also
contains some VOC, which may be environmentally unacceptable.
According to the TAACOM CPC acquisition document dated September 16, 1993,
the HMMWV vehicle is supposed to have a service life of 20 years with a minimum
of 15 years. The vehicles need to be corrosion resistant for extended periods in cor-
rosive environments involving one or more of the following conditions: high humid-
ity, salt spray, road deicing salts, gravel impingement, atmospheric contamination,
and temperature extremes. There shall be no corrosion past stage one, nor corrosion

TABLE 4.50 CARC Paint System Performance
Number of HMMWV with Deteriorated
Coating
Category Number of HMMWV Number Percent

Army 1 17 4 24
Army 2 13 9 69
Army 3 9 3 33
Army 4 11 11 100
Marine Corps 2 30 75
Marine Corps 40 30 75
WI National Guard 29 13 45