Protective coatings from Rhino Linings limiting leaks in wastewater infrastructure

Protective coatings
from Rhino Linings Australasia are helping the water and wastewater industry
reduce leakage and save money on infrastructure repairs.

Corrosion is a major
problem in the industry affecting various assets including pipelines, storage
tanks and treatment plants. Corrosion and the subsequent leakage can cost the
industry in excess of a billion dollars each year. Ageing infrastructure
requires refurbishment or replacement; one method of refurbishment of water
industry assets is to carry out surface repairs and then apply protective
coatings.

Rhino Linings is an
American corporation based in San Diego, and manufacturing a range of spray
applied polymer coatings for more than 30 years. Rhino Linings Australasia was
formed in early 2000 through the acquisition of a local coatings company with a
view to establish manufacturing and distribution in Australasia.

Based on the Gold
Coast, Rhino Linings Australasia is the only manufacturer of spray applied
coatings in Australia. The company sources all its materials from local
suppliers except for a few specialised chemicals, which are imported from the
parent company in America. Being a local manufacturer allows the company to be
more responsive to customer requests.

Dennis Baker,
Special Projects Engineer at Rhino Linings explains that there is no dependency
on delivery schedules from an overseas supplier, allowing their applicators and
customers to begin large projects without having to wait months for supply of
material.

When refurbishing or
repairing any pipes, channels or tanks that carry potable water, special
coatings are required to prevent any chemical from leaching into the drinking
water. Different coatings can be applied to the inside and outside of pipelines,
especially if the pipes are buried in ground. Concrete storage reservoirs are
lined on the inside to stop corrosion and prevent leaks.

For wastewater and
sewerage treatment infrastructure such as clarifier tanks and sewage channels, the
structure of the polymer has to be resistant to abrasion and chemical attack. According
to Baker, special consideration has to be given when coating structures in sewerage
treatment plants. For instance, one of the by-products of sewage is hydrogen
sulphide gas, which can form sulphuric acid when mixed with water vapour.

A major
consideration in any surface treatment process is the need to minimise downtime,
which is met by Rhino Linings’ coatings with their rapid setting. While Pure
Polyurea has a cure time of six seconds after spraying, Polyurethane sets in 20
seconds.

Rhino Linings’ ‘high
build coatings’ are 1000 microns thick as opposed to paints and epoxies, which
might only be several hundred microns. High build polymer coatings can also stretch
and shrink as substrates expand and contract due to temperature and ground
fluctuations.

All coatings
developed by Rhino Linings for the water industry are continually tested at the
Australian Water Quality Centre in Adelaide to ensure compliance with the
latest standards including AS4020, which is regularly updated.

The Rhino Linings
Polyurethane and Pure Polyurea coatings have a patented mix ratio that has been
determined over many years. There is no solvent or VOC content in the polymer coatings
while application procedures contain and manage overspray.

A Rhino Linings
Applicator recently completed a project for the Hospital Hill Reservoir in
Murwillumbah, NSW. The project scope required the applicator to repair the
inside and outside of the 80-metre diameter, above ground steel potable water
storage tank. The tank sits on a concrete ring beam with the floor of the tank in
a series of concrete segments. The repair was necessitated by the failure of
the expansion joints in the floor leading to leakage in the tank. The joints
were resealed and a Rhino Pure Polyurea coating applied over all the floor
joints, the ring beam and a further 500mm up the side of the tank.

To prevent entry of water
or material between the coating and the substrate, terminating grooves were cut
in the floor concrete and the edge of the coating bevelled by special
termination tape with a wire that cuts the polymer at an angle as the tape is
removed. Baker explains that their polymers, when correctly applied, have
attachment loads of 6 to 10 mPA, adding that the concrete substrate would give
way before the coating peeled off.

The substrate is
prepared properly before the coating application by ‘profiling’ the surface of
the structure to the appropriate standard. Profiling involves blasting sand or
similar material at a surface under high pressure to roughen the surface, which
allows the coating to better adhere to the substrate.

To ensure the polymer
coatings are applied correctly, all projects endeavour to comply with
Australian Standard 3894, which requires the completion of such elements as
substrate condition, weather condition and time reports. Completion of the
reports acts as a reminder to the person applying the polymer that the
appropriate conditions existed at the project site for the safe and effective
application of a coating.

Various hold points
in any project allow for checking the preparation, primer and coating
application by accredited inspectors who can certify that the work conforms to
the standard. Larger Rhino Linings Applicators have a NACE or ACA inspector on
staff or have a very good relationship with a local inspector.

NACE is the National
Association of Corrosion Engineers and ACA is the Australasian Corrosion
Association, with both organisations providing technical training and
certification programs, hosting conferences and working with industry and
academia to develop relevant standards. Rhino Linings recognises and works with
both organisations. For the NSW water storage reservoir, the surface was given
a Class 2½ blast profile as specified by the relevant Australian Standard.

For steel surfaces,
a Rhino primer is used to further improve adhesion following which the coating
is applied. For concrete, the profile used is usually between 3 and 5 according
to the standard profiles established by the International Concrete Repair
Institute. After profiling, a Rhino primer is again applied followed by the
polymer coating spray.

Accessibility to a project site is an important
planning issue. Rhino Linings Australasia assists its dealers in developing
best practice for chemicals and machinery to be driven to the site or
transported by rail, road or sea to the nearest location.