Page 214 - Trenchless Technology Piping Installation and Inspection

178 Cha pte r F o u r

concrete, plastics, and composites, as well can also undergo forms
of corrosion or environment-/stress-related deterioration that are
perhaps not now quite as obvious or known to many pipeline
practitioners.

Corrosion Protection—Ductile Iron Pipe American National Standard
Institute (ANSI) and American Water Works Association (AWWA)
have developed multiple standards for corrosion protection of iron
pipe and fittings. These standards include ANSI/AWWA C104/A21.4
for internal cement-mortar lining, ANSI/AWWA C105/A21.5
for polyethylene encasement (this standard also contains a soil-
evaluation procedure in the appendix that is helpful for practitioners
to determine when standard pipes with thin asphaltic shop coatings
can be direct buried in specific soils and when the supplementary
polyethylene wrap should be applied as opposed to installing stan-
dard pipe without wrap), and AWWA C116 for fittings that in their
normal production processes are coated inside and outside with
fusion-bonded epoxy (FBE) instead of cement mortar.
More recently and building on these standards and other exten-
sive experience, CORRPRO Company working with DIPRA as well
as ductile iron pipe manufacturers has conducted a 2-year study of
corrosion and corrosion-protection characteristics. This study has
included field and laboratory evaluations related to short- and long-
term polarization rates under varying conditions, corrosion-rate
reduction, and corresponding cathodic current criterion. This infor-
mation was then analyzed in conjunction with an extensive database
from 1379 physical inspections of buried iron water lines. The result
of the study is a risk-based corrosion protection design strategy for
buried ductile iron pipelines referred to as the design decision model
(Kroon et al., 2004 and Bonds et al., 2004).

Corrosion—Steel Pipe The steel pipe industry has also been proactive
in readily recommending and providing corrosion protection mecha-
nisms to end users, despite the higher costs of some processes. Accord-
ing to the steel pipe industry, “Corrosion protection systems that
include coatings, monitoring systems, and cathodic protection
(installed incrementally as needed) are very cost effective.” There are
a number of standards and processes for both internal and external
corrosion protection of steel pipe, including cement-mortar lining,
paints and polyurethane linings, tape coatings, coal tar enamel coat-
ings, cement-mortar coatings, and epoxy and polyurethane coatings.
Furthermore, the steel pipe industry acknowledges the use of cathodic
protection as an effective and/or necessary method of protection to
complete the corrosion protection process.

Corrosion of Concrete, Composite, and Plastic Pipes All common pip-
ing materials can be deteriorated or corroded and designers should