Page 432 - Corrosion Engineering Principles and Practice

400 C h a p t e r 1 0 C o r r o s i o n i n S o i l s a n d M i c r o b i o l o g i c a l l y I n f l u e n c e d C o r r o s i o n 401

Composite

3-layer PE
Fusion-bonded Epoxy

PE Tape
Extruded 2-layer PE
Asphalt

Wax Tape
Coal Tar

1940 1950 1960 1970 1980 1990 2000 2010

FIGURE 10.4 External pipeline coating development.

copper service lines may be used. Because of these differences, the
approach to the protection of such components is likely to differ in that
more emphasis is placed on the use of small ICCP units and galvanic
anodes, even when the metal surface is protected by a coating.
Gathering Systems
Gathering systems do not ordinarily differ much from pipelines.
They offer more variety and often have more accidental contacts.
ICCP systems may encounter more interference problems in both
directions. One common problem is that gathering lines, particularly
in the early development of a field, may be laid in great haste, with
little or no thought to the corrosion control problem. Although this is
not, strictly speaking, a difference in corrosion behavior, it does
account for some serious problems.
Plant Piping
The corrosion activity in a refinery complex piping network or in any
other industrial plant has several unique features:

• First, there are always combinations of aboveground and
underground piping
• A considerable variety of sizes, materials, and functions
• Almost invariably a great variety of coatings applied in
original construction, creating a range of surfaces from bare
to very well-coated
Another factor present in almost every plant is the large amount
of bare copper in the ground system, typically a collection of ground