There are many applications where coatings are used ranging from
electrical junction boxes and conduit to stadium seating and from cable
supports to the coating of submersibles. The primary reasons why such
coatings are used by the construction industry are the corrosion
protection that can be offered as well as UV protection, beautification,
and mechanical protection.
Pipe Coatings - Seattle
Thermoplastic coating is used by the Seattle Public Utilities for the
protection of pipes and fittings in the often highly corrosive soils of
Terminal 18 re-development of Harbor Island. They examined the ductile
iron pipe after five years and found it to be “as new” while the PVC
tape wrap had already deteriorated. The project work has not only
resulted in the thermoplastic coating being established as the coating
standard for Seattle's water distribution mains, but also an increased
demand across the United States.
Recent projects utilizing this process have included waste water
plants in Snohomish and the Olympus Terrace Sewer District at Mukilteo,
both in Washington State, through to baggage racks for Alaska airlines.
Thermoplastic functionalized polyolefin alloys have been used for
coating of water pipes for many years. On a project in Sweden using
similar compounds, The Swedish Corrosion Institute dug up the pipes
after 10.85 (11) years in the salty clay soils around Gothenburg. These
are the results after 11 years:
Rusting - Zero Cracking - Zero Blistering - Zero Flaking - Zero Adhesion - 100%
These results have indicated to the Gothenburg Water and Sewage Works
a lifetime for the pipes in the ground of over 200 years. The
experience in Sweden has spread to other parts of the world.
Principally, the UK, Australia, New Zealand and the Middle East.
These coating processes have also been used for their chemical and
abrasion resistance in slurry and chemical pipes. They have been used in
Washington and the Pacific North West in general for gas pipes and for
the internal lining of sewage pumps and fittings carrying grit and
gravel (see above). Again 1 and 3-year tests showed no wear at all.
The process is being evaluated for road culverts to carry salt and
grit from the roadside in winter. It has been tested to ASTM A 926-94,
which subjects a coated cylinder to a number of cycles in a mixture of
salt and grit – like a washing machine. After one million cycles all
other coatings – which included fusion bonded epoxy and galvanizing –
were completely stripped. With thermoplastic technology, over half the
coating still remained. No other coating met this performance!
Finally, this process is also used in automotive under-body
applications, not only for the corrosion protection but also because
they can pass the stone chip tests at only 16 mils. These coatings are
now starting to be used and specified by Nissan, Renault and General
Motors amongst others (SAE J400).
In summary the advances in thermoplastic coating products over recent
years combined with the improvements in grinding technology have
enabled functionalized thermoplastic powders to be more available for
both fluid bed and electrostatic spraying. In addition 12 years of
laboratory testing and field experience has shown that such coatings
really can provided very long term corrosion protection and abrasion
resistance even in very harsh and salty environments as well as having
the advantages of no TGIC, no phthalates, no halogens, no VOCs, no
isocyanates, and very low toxicity on burning.