Advances in Antifouling Coatings Technology
these biocides on the environment, enzyme-based antifouling paints are proposed as a bio-based, non-accumulating
alternative. Scientists tested a hydrogen
peroxide-producing system composed
of hexose oxidase, glucoamylase and
starch for the chemical and physical
functionalities necessary for successful incorporation into a marine coating. The activity and stability of the
enzymes in seawater was evaluated at
different temperatures, and paint compatibility was assessed by measuring the
distribution and activity of the enzymes
incorporated into prototype coating formulations. The scientists used a biomi-metic encapsulation procedure for HOX
through polyethylenimine-templated
silica co-precipitation. Silica co-precipitation significantly improved the stability and performance of the antifouling
system in marine-like conditions.
• New biocide free, two-component,
fouling release coating.
Non-stick fouling release coatings are
based on a technology which prevents the
adhesion of fouling organisms by providing a low-friction, ultra-smooth surface
on which organisms have great difficulty
in adhering. The coatings do not inhibit
the fouling settlement, but provide self-cleaning when sailing at a certain speed at
a certain activity, typically minimally 15
knots at minimum 75 percent of the time.
Fouling release coatings have their origin in the desire for a biocide-free system
and have been in existence for 30 years.
On these types of coatings fouling is not
prevented from settling, as in the case of
traditional antifouling, but in practice
the bond between the fouling organisms
and the coating surface is so weak that
it breaks by the weight of the organism
itself or by the water pressure and current
to which it is exposed.
• Copper-Free Antifouling coating
CuO is a still a very effective biocide but it
requires a high concentration to give fully
effective protection against most types
of marine fouling. Paints that contain
less copper metal, or use less powerful
ingredients such as copper thiocyanate,
often contain extra biocides such as zinc
pyrithione or organic algaecides to cope
with slime and weed growth. It is these
organic boosters that are currently caus-
ing a stir, as some people think they could
cause similar problems to TBT.
One of the latest biocides to be authorized is Selektope (generic name
medetomidine), made by the pharmaceutical giant AstraZeneca. Instead of
killing off marine growth, it is said to
temporarily stimulate the octopamine
receptor in the larvae of molluscs, causing them to be harmlessly repelled from
the hull. Various research has apparently proved that it works at extremely
low concentration levels ( 3 g/L) in any
paint, and needs no other biocide for a
barnacle-free hull. Sadly it’s not as effective on weeds, so paint formulations will
also have to contain approved algaecides
to be effective.
• Self-adhesive /fouling-release coatings.
The ‘eSHaRk’ (eco-friendly Ship Hull
film system with fouling Release and
fuel-saving properties) project aims to
bring to the market a fouling-protection
technology which not only maintains
the current state-of-the-art fouling-protection standards, but is superior to
existing paint-based solutions in terms
of eco-friendliness, ease of application,
robustness and drag-reduction effects,
all of which will lead to fuel savings and
the reduction of GHG (greenhouse gas)
emissions.
The system incorporates a fine-tuned
fouling-release system based on PPG’s
100% silicone binder technology and a
self-adhesive film designed by MACtac
for underwater use. As part of the ‘
eSHaRk’ project, new, robotized application technology is being developed by
VertiDrive that will be used to automate
application of the film on large commercial vessels. Furthermore, the surface
morphology of the film will be optimized
to enhance drag-reduction, fuel-savings
and emission-reduction benefits to previously unattainable levels.
• Nano antifouling coating
A number of manufacturers have come
up with some sensible and effective al-
ternative coatings, but none of them has
solved the problem completely. But some
interesting new products are on trial at
the moment, which could well come to
fruition within the next decade.
Among these are Teflon- and silicone-based nanotech coatings, using technology already found in marine gel coat
polish. Cornwall-based Nanotech Marine
is working on a self-cleaning nanotech
antifoul and the first three-year test results look promising. It’s only intended
for motorboats at the moment, but the
company is looking into ways of applying the same principles for sailing boats.
Nanotech Marine’s antifoul is a
silicone-based product, said to create a
surface so slippery (at a molecular level)
that no weed or mollusc can get a grip
on the hull. Research has shown it does
indeed work, but only on boats capable
of high speed ( 10 knots or more), which
are used regularly, as the coating relies
on the boat’s motion through the water
to wash off biofouling. They’re not so effective for a boat left on a mooring or
in a marina for weeks on end, so even if
one has a fast yacht, a nanotech coating
may have to be used in conjunction with
another product, such as an ‘ultrasonic’
bio-deterrent system.
Conclusion
Companies are investing a lot in research
and development to expand the efficiency of antifouling coatings which, in
turn, is expected to increase the demand
from end-users. Technology advancement
worldwide is one of the trends expected
to add to the growth of the global anti-fouling coatings market.
Increased demand for oil and gas, increasing population and urbanization are
drivers for the growth of the antifouling
coatings market. These are also widely
used for the protection of structural infrastructure and machinery in rigs. One
of the major challenges faced by the
antifouling coatings market is predictable decline in the shipbuilding industry.
The market has also been witnessing the
growing consumer preference for eco-friendly products due to which strict
environmental regulations have been imposed that pose a challenge to the growth
of this market. CW
