Page 287 - Corrosion Engineering Principles and Practice

260 C h a p t e r 8 C o r r o s i o n b y W a t e r 261

Factor Explanation
Thrust restraint Inadequate restraint can increase longitudinal stresses
Pipe lining and Lined and coated pipes are less susceptible to corrosion
coating
Dissimilar metals Dissimilar metals are susceptible to galvanic corrosion
Pipe installation Poor installation practices can damage pipes, making them
vulnerable to failure
Pipe manufacture Defects in pipe walls produced by manufacturing errors can
make pipes vulnerable to failure
Environmental
Pipe bedding Improper bedding may result in premature pipe failure
Trench backfill Some backfill materials are corrosive or frost susceptible
Soil type Some soils are corrosive; some soils experience significant
volume changes in response to moisture changes, resulting
in changes to pipe loading
Groundwater Some groundwater is aggressive toward certain pipe
materials
Climate Climate influences frost penetration and soil moisture.
Permafrost must be considered in the north
Pipe location Migration of road salt into soil can increase the rate of
corrosion
Disturbances Underground disturbances in the vicinity of an existing pipe
can lead to actual damage or changes in the support and
loading structure on the pipe
Stray electrical Stray currents cause electrolytic corrosion
currents
Seismic activity Seismic activity can increase stresses on pipe and cause
pressure surges
Operational
Internal or transient Changes to internal water pressure will change stresses
water pressure acting on the pipe
Leakage Leakage erodes pipe bedding and increases soil moisture in
the pipe zone
Water quality Some water is aggressive, promoting corrosion
Flow velocity Rate of internal corrosion is greater in unlined dead-ended
mains
Backflow potential Cross connections with systems that do not contain potable
water can contaminate water distribution system
O&M practices Poor practices can compromise structural integrity
and water quality

TABLE 8.2 (continued)