Page 644 - Corrosion Engineering Principles and Practice

602 C h a p t e r 1 4 P r o t e c t i v e C o a t i n g s 603

C : Very high industrial—industrial areas with high humidity and
5-I
aggressive atmosphere
C 5-M : Very high marine—coastal and offshore areas with high salin-
ity

Containment multiplier guidelines are included to aid in
developing approximate costs for paint removal depending upon the
containment type. These are to be used in conjunction with surface
preparation costs.
Decisions involving whether or not a full repaint is required, as
opposed to a maintenance repaint or touch-up, should be based on
the results of an investigation. Generally, touch-up procedures are
used when the amount of corrosion is limited or found in discrete
areas. The success of maintenance repainting depends on the coating
type, thickness, and adhesion of the existing coating system, as well
as the substrate condition. The general procedures outlined in this
guide may be used to determine installed costs and life-cycle costs for
any combination of maintenance painting sequences.
Cost comparison examples are presented in the guide in the form
of detailed worksheets following the basic economic principles of net
present value and linear depreciation.

14.5 Organic Coatings
Organic coating materials have increased in complexity in parallel
with developments in surface science and engineering, coating
technologies, and environmental requirements. More can be
achieved by the use of a proper coating material today than by
simply covering a surface to reduce contact of an environment with
the substrate. Of prime importance in the development of high-
performance organic coatings was the petroleum industry, which
produced most of the basic ingredients from which synthetic resins
were developed.
The cracking of petroleum produced a multitude of unsaturated
workable compounds that are important in the building of large resin
polymers such as vinyls and acrylics. The solvents necessary for the
solution of the resins were also derived from petroleum or natural
gas [11]. The building blocks for epoxies and modern polyurethane
coatings are other derivatives produced by refining petroleum
products. Table 14.4 summarizes types of coatings, properties, and
applications for a wide range of modern coating systems [12].
14.5.1 Coating Functionality
Some important considerations for designing corrosion-resistant
coatings include coating protection, component design, component
function, and coating formulation. Many coatings contain as
many as 15 to 20 ingredients with their own range of functionality.