The development of oil and gas fields at increasing depths in recent years,
both onshore and offshore, and the need for pipelines to carry viscous media
such as oil sands at high temperature to improve flow efficiency, has created
a requirement for the coatings used to protect such pipelines from corrosion to
be able to operate in a temperature range 120-150oC. One of the most
successful coating types for the corrosion protection of steel pipes is Fusion
Bonded Epoxy (FBE) powder coatings but, until now, the range of options
available for pipelines operating at high temperatures has been mainly limited
to either a standard FBE applied at a higher film thickness or as a dual-layer
system, or an FBE with a high glass transition (Tg) of the film, applied as a
primer for a 3-layer polypropylene system.
Whilst it is widely accepted that it is preferable for the Tg of the coating film to
be at least 10oC above the operating temperature of the pipeline there are few
FBE coatings commercially available with a film Tg in the range 130-160oC to
allow them to be used at the higher operating temperatures now required.
The few that do exist have relatively limited flexibility particularly at low
temperatures which limits the range of environmental conditions that pipelines
coated with such products can withstand.
This paper presents the development of a range of Mid-Tg-FBE powder
coatings with film Tg’s in the range 130-150oC and test methods with
conclusions. These coatings demonstrate excellent adhesion and mechanical
performance, even at temperatures down to -60oC, thus greatly expanding the
range of field conditions and pipeline operating temperatures that can be
accommodated. The excellent flexibility of these coatings enable them to be
applied as a single-layer FBE coating, and as a dual-layer FBE coating
system, as well as a primer for 3-layer polypropylene systems. The growing
commercial track record of these products is confirming the excellent results
seen in production and laboratory testing.