Page 283 - Corrosion Engineering Principles and Practice

CHAPTER 8

Corrosion by Water

8.1 Importance of Water
The amazing view of earth from space shows how the blue planet we
live on is unique among the other known celestial bodies. It has water,
which covers three-fourths of its surface and constitutes 60 to
70 percent of the living world. Actually, only one percent of this water
is fresh and directly usable. Approximately 97 percent of the planet
water is salty seawater and two percent is frozen in glaciers and polar
ice caps. However, abundant supplies of fresh water are essential to
industrial development.
Enormous quantities of water are required for cooling systems,
process needs, boiler feed and for sanitary and potable water. It was
estimated, in 1980, that the water requirements for industry in the
9
United States approximated 525 × 10 L/day. A substantial quantity
of this water was reused. The intake of “new” water was estimated
to be about 140 × 10 L/day [1]. If this water was pure and contained
9
no impurities, there would be little need for water conditioning or
water treatment.

8.2 Corrosion and Water Quality and Availability
North Americans use a lot of water. Annually, approximately 63 × 10 m
3
9
of drinking water serves approximately 73 million customers in North
America, with the average total water-use rate per customer ranging
between 475 and 660 L/capita/day. Recent benchmark estimates by the
American Water Works Association (AWWA) on indoor water-use rates,
indicated an average use-rate of 245 L/capita/day. The average con-
sumer cost for clean water ranges from $0.12 to $0.65/m .
3
According to the AWWA industry database, there was in 1995
approximately 1.5 × 10 km of municipal water piping in the United
6
States. The sewer system consisted of more than 16 thousand
publicly owned treatment facilities releasing some 155 × 10 m
6
3
of wastewater per day. The total annual direct cost of corrosion
for the nation’s drinking water and sewer systems was estimated at
257

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