Page 64 - Reliability and Maintainability of In service Pipelines

Pipeline Inspection and Maintenance 53

Figure 2.2 Corrosion of a steel pipe in a factory in Taiwan.

previously in Section 1.4, for each material type reacts differently to different
chemicals, whether it be the substance contained within the pipe or the environ-
ment surrounding the pipeline itself.
Clay is a very brittle substance, but has proven to withstand the natural and
aggressive elements of soils in which the pipelines are buried. But substances
flowing through these pipes need to be chosen very wisely to prevent corrosion
from occurring.
Concrete pipe corrosion occurs predominantly due to the reinforcement on the
inside. Once the steel reinforcement is exposed to oxygen, rust starts to form and
causes further deterioration. Sulfide corrosion in concrete sewers can also be
prominent.
Metal pipelines are most vulnerable to corrosion due to rust as explained pre-
viously. Also metals react with some gasses and at high temperatures, which
accelerates corrosion.
Corrosion in plastic pipes occurs due to heat exposure, this changes the struc-
ture of the plastic thus causing it to deform, thinner walls of the pipeline can be
the consequence. This increases the likelihood of cracks, leakages, and ruptures.