Page 228 - Challenges in Corrosion Costs Causes Consequences and Control(2015)

206 CORROSION CONTROL AND PREVENTION

TABLE 4.1 Costs of Corrosion Control Methods and Services
Range Average Cost
Material and Services ($× billion) ($× billion) Percent
Protective coatings Organic coatings 40.2–174.2 107.2 88.3
Metallic coatings 1.4 1.4 1.2
Metals and alloys 7.7 7.7 6.3
Corrosion inhibitors 1.1 1.1 0.9
Polymers 1.8 1.8 1.5
Anodic and cathodic 0.73–1.22 0.98 0.8
protection
Services 1.2 1.2 1.0
Research and 0.02 0.02 <0.1
development
Education and training 0.01 0.01 <0.1
Total $54.16–188.65 121.41 100

4.2.1 Organic Coatings

The major organic coatings are often classified by a curing mechanism, with the two
basic types of cured coatings being nonconvertible and convertible (4). The noncon-
vertible coatings cure solely by evaporation of the solvent with no chemical change
in the resin matrix. They can be redissolved in the solvent originally used to dissolve
the resin. Convertible coatings, on the contrary, cure primarily by a polymerization
process in which the resins undergo an irreversible chemical change.

4.2.1.1 Nonconvertible Coatings The common types of nonconvertible coatings
are the following:

Chlorinated Rubbers. Elastomers formed when natural rubber or a polyolefin is
reacted with chlorine. These materials are usually modified by other resins to
obtain high solid contents and to decrease brittleness.
Vinyls. These are made by dissolving polyvinyl chloride (PVC) polymers in a suit-
able solvent. They are generally low solid coatings applied in very thin coats.
Vinyl coatings are used for their weathering ability.
Acrylics. These are made by dissolving polymers made from acrylic acid and
methacrylic acid or acrylonitrile. Water-based acrylics are widely used because
of their weathering properties and ease of application.
Bitumen. Generally based on residues from petroleum or coal mining processes.
Bitumen coatings can also come from naturally occurring sources such as
gilsonite. The presence of some aromatic hydrocarbons such as benzene in
some of these coatings has limited their acceptability in recent times because
of environmental and health concerns.
Flame-Spray Polymers. These are nonevaporative cure coatings. These coatings
function by cooling from the molten state. The molten polymer hits the surface