Page 270 - Challenges in Corrosion Costs Causes Consequences and Control(2015)

248 CORROSION CONTROL AND PREVENTION

in production fields have a much more significant problem with internal corrosion
than the typical transmission pipeline.
One of the options available for mitigating internal corrosion is chemical treat-
ment of the product being transported. Chemical corrosion inhibitors for mitigation
of corrosion and biocides to prevent microbiological activity and hence microbial
enhanced corrosion may be used. Both of these methods have been found to be effec-
tive in either natural gas or liquid pipelines. The cost of either the chemical corrosion
inhibitor or biocide is significant. It should be noted that very large volumes of prod-
ucts are continuously flowing through the pipeline. To mitigate corrosion through the
chemical treatment requires continuous injection or regular batch treatment of the
inhibitor or biocide.

4.11.4 Operations and Maintenance

Significant maintenance costs for pipeline operation are associated with corrosion
control and integrity management. The driving forces for the expenditure of mainte-
nance dollars are to preserve the asset of pipeline, which is equal to $93.3 billion in
book value and $541 billion in replacement value and to ensure safe operation with-
out failures that jeopardize public safety, result in lost product and throughput, and
cause property and environmental damage that is estimated at $470–870 million/year.
A survey of major pipeline companies indicated that the primary cause for the loss
of corrosion protection was coating deterioration (30%) and inadequate CP current
(20%). Other contributing causes were shorts or contacts of about 12% and about 7%
because of stray current. Most of the general maintenance consisted of monitoring
and fixing these problems. Integrity management concerns are focused on conditions
assessment, mitigation of corrosion, life assessment, and risk modeling.
The use of coatings in conjunction with CP is the most popular form of corro-
sion protection of pipelines. Some of the coatings used are fusion-bonded epoxy,
extruded polyethylene, coal tar enamel, liquid epoxy, tape, polyurethane, mastic, and
wax. Pipelines with each of these coatings remain in service at the present. The most
widely used coating on pipelines is fusion-bonded epoxy. New multilayered coatings
are now on the market.
Coatings have been specified for all new pipelines since the 1960s. The aver-
age cost of coating pipe for new construction is estimated at $24,000/km and for a
total length of 778,900 km the total coating corrosion prevention can be estimated at
$18.4 billion in replacement costs.
Nearly 30% of the operational pipeline corrosion problems are attributed to coat-
ing deterioration. A large portion of corrosion control costs is because of monitor-
ing, identifying, and repairing coating anomalies. Coating deterioration also affects
the ability and effectiveness of CP. Thus, to extend the operating life of a pipeline,
pipeline rehabilitation (recoating the pipeline) is recommended.
CP is the required method of corrosion control of buried pipelines. The two forms
of CP are impressed-current and sacrificial anode systems. Both forms of protection
have been in use in industry for quite some time and the industrial personnel are
familiar with their installation and operation (NACE Standard RPO169-96).