The anti-corrosion protective coating system is comprised of a liquid adhesive (primer),
a corrosion prevention layer of tape (inner layer)
and a mechanical layer of tape (outer layer). The primer is applied directly to the pipe surface to assure that
the inner layer of tape is permanently and strongly bonded to the pipe. The inner and outer layers of tape
have polyethylene (PE) backings with butyl rubber based adhesives. The PE backing is formulated differently
for the inner layer and outer layer due to the different properties that are desired. The inner layer mostly
consists of low density PE which allows it to be conformable to the pipe surface. The outer layer has more
high density PE to allow the tape to be conformable, but also provide protection to the inner layer from
damage during storage, transportation, installation and throughout the lifetime of the pipeline.
The adhesive in both tape layers are composed of butyl rubber, hydrocarbon resin, filler, oil and antioxidant.
Butyl rubber is used due to its molecular structure of low unsaturation levels, which yield unique
characteristics. These characteristics include: chemical and moisture resistance, thermal stability,
weathering and gas permeability; all essential properties required for long term in-ground performance.
The adhesive of the inner layer is formulated to work in conjunction with the primer to form a strong bond
to the steel substrate. This bond provides the corrosion protection and long term performance that the
pipe requires. Additionally this bond is critical to preventing cathodic disbondment and increasing the
shear adhesion of the inner layer to the pipe to reduce the effect of the stress imparted by the soil.
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