Page 284 - Corrosion Engineering Principles and Practice

258 C h a p t e r 8 C o r r o s i o n b y W a t e r 259

$36 billion, which included the costs of replacing aging infrastructure,
unaccounted-for water through leaks, use of corrosion inhibitors,
internal mortar linings, and the cost of external coatings and cathodic
protection [2].
Based on AWWA data, there was approximately 1.4 × 10 km of
6
municipal water piping in the United States in 1995. Table 8.1 presents
an estimated profile of the different materials that make up these
water pipes. New pipes are being installed at a rate which extends the
system length by 1.5 percent per year, while an additional 0.5 percent
is being replaced annually.

8.2.1 Corrosion Impact
Water possesses several unique properties, one being its ability to
dissolve to some degree most of the inorganic substances occurring
in nature. Because of this essential property, water typically contains
a variety of impurities that may cause problems through the
formation of deposits in water lines, on boiler tubes, and on any
other surface water comes in contact with. Dissolved oxygen, which
supports the aquatic life, is also responsible for the corrosivity of
water toward metals. Corrosion jeopardizes the reliability of water
delivery systems by causing leaks and breaks and by affecting water
quality. Corrosion can have a variety of impacts grouped into the
following four categories [3].
Health and Regulations
From a health standpoint, the most significant metal that can enter
the drinking water via corrosion is lead. The contribution of drinking
water to the total daily intake of lead in the United States is estimated
to be approximately 20 percent. In drinking water, the primary
sources of lead are lead service lines, lead plumbing, brass fixtures,
and 50:50 tin-lead solder used to join copper piping. Lead enters the
water when the water has been standing motionless in contact with
the lead source for extended time periods.

Material Percentage
Cast iron 48
Ductile iron 19
Concrete and asbestos concrete 17
PVC 9
Steel 4
Other 2

TABLE 8.1 Profile of Different Materials Used for U.S. Transmission Water
Pipes, as Determined from the 1992 AWWA Water Industry Database [2]