20
COATINGS
A coat for all seasons
Paul Moore spoke to three of the world’s leading suppliers of industrial paints and
coatings about the mining market, and the challenges of supplying the right solution
roke
yle
“Abrasion
is one of
the major
environmental
conditions in
mining that
impacts the
performance
of coatings”
Atlas Copco
Boltec LC,
Kittila mine,
Finland
P
aints and coatings are used on
mobile mining equipment, both
surface and underground, but also
on fixed installations such as conveyors,
crusher stations, thickener tanks and the
process plant buildings.
Mining presents a series of unique
challenges for coatings suppliers, not
least that operations are normally 24/7,
with climate extremes, the presence
of abrasive rock dust, often constant
exposure to water and sometimes
harsh chemical environments in the
processing plant.
Coatings specialists formulate a range
of products to cope with this wide
range of conditions. Mining equipment
and structures are expensive assets;
more so if a structure fails or collapses
and production stops for a couple of
days. By comparison, the coatings
industry therefore regards the cost of
a good coating as small.
Eric Schomburgk is senior market
development director for mining at
Sherwin-Williams Protective & Marine
Coatings is based in Santiago, Chile.
He comments: “Mining is conducted in
a very aggressive environment, which
may include exposure to abrasion. This
pertains to all of the dry processes like
extraction of the mineral, transport in
conveyors, crushing and milling.”
He adds: “There is also the presence
of water, which includes wet, corrosive
processes like flotation of the mineral and
thickening of the concentrate. Most of
the base-metal refining processes are
conducted in acid environments, while the
electro-winning process is carried out in a
very aggressive and corrosive sulphuric
acid environment.
“The gold process uses cyanide salts
and requires high alkaline solutions to
prevent reaction to cyanhydric acid, so
these conditions are very corrosive too.
Final non-metallic mineral-mining
environments, such as for lithium salts,
potassium nitrates and phosphates, are
also very corrosive because of the salt
solutions associated with the process.”
On the subject of abrasion, Jason Bolz,
commercial manager at Valspar General
Industrial, says: “Abrasion is one of the
major environmental conditions in mining
that impacts the performance of coatings.
Depending on the type of mining – from
copper to gravel to iron ore – equipment
needs to move hard, abrasive material
from location to location within the
mining environment. A durable, quality
coating made by a reputable company
is designed to withstand this type of
harsh environment.”
In terms of different solutions to
different challenges, International Paint
approaches the market from a system
point of view, with each layer of coating
designed to perform selected functions.
Jon Wilson, market manager – mining
at International Paint (part of Akzo Nobel),
says: “Our extensive product range has
systems for steel and concrete that offer
chemical, temperature and abrasion
resistance in addition to corrosion
protection. Mining has such a range of
product requirements that it is worth
speaking to us early on in a project to
ensure the best solution is used for
specific needs.”
Each mining location has its own
unique micro-environment, so the coating
solution has to be fit for purpose,
taking into account a great number of
parameters such as moisture, the chemical
environment and abrasion. So for each
project, the customer’s requirements must
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COATINGS
Coating chemical groups used in mining
• Epoxy polyamides
• Cycloaliphatic amine
• Phenalkamines
• TETA and DETA adducts
• Epoxy novolacs
• Aliphatic acrylic polyurethanes,
• Aliphatic polyester polyurethanes
• Polysiloxanes
• Polyureas
• Vinyl esters
• Novolac vinyl esters
• Zinc inorganics
• Zinc epoxy rich primers
• S pecial acid-resistant floor systems for concrete
Centre picture:
processing plant,
Lihir Gold, PNG
Russia-made
shovel,
Chernigovets
mine, Siberia
be considered, along with the
environment, regardless of whether the
project is above or below ground.
A mixture of local and multinational
paint and coatings companies supply the
mining industry, but projects are
becoming more multinational with an
associated need to supply the same
quality of products globally, as well as
the all-important service back-up across
multiple geographies.
Small companies are also less likely to
be able to make the necessary investments
in R&D to develop, support, sell and
promote the coatings technologies
needed in the mining industry, or to
dedicate manpower to focus resources on
this specific growth market.
In the mining market, Sherwin-Williams
states that it has two routes to supply
anti-corrosive protection to equipment
and structures. With new projects,
specifications are determined by EPCM
groups, while for maintenance of existing
assets, the plans and specifications usually
come from the mining companies’ own
maintenance engineers.
Mr Bolz adds: “Valspar’s goal is to
develop materials that are flexible and
robust enough to perform equally well in
a variety of environments. Coatings used
by OEMs for mining equipment are
formulated to withstand the rugged
environment so that regular repainting
isn’t required.
“We anticipate that an undisturbed
coating – one that did not have an
accident/impact – could withstand more
than 15 years in most environments
before requiring repainting. In extremely
harsh environments where trucks and
equipment can collide with rocks,
coating touch-up will be required more
frequently.”
Coating types used
The actual paint/coating solution selected
will depend on the type of mining process
and owner’s maintenance demands.
The coatings specialist will recommend
the best product with the highest
chemical resistance for each step of
the process.
The performance of a coating is
dependent on thickness, formulation,
environment and surface preparation.
Powder coatings, which are baked on
to metal, are not widely used on larger
mining equipment units and installations,
but are instead found on small items that
can be easily replaced.
For large steel machines and installations,
solvent-based coatings represent the best
solution for long-term performance.
While powder coatings can deliver the
required performance properties, the
major reason they are not used on mining
structures and equipment is that they are
impractical given the physical size of the
equipment, and the fact that the coatings
have to be heated to 200ºC. It would
also not be economical to put that much
coating material through a heating process.
One of International Paint’s key mining
products is Interzone 954, which, it states,
offers an “excellent balance of corrosion,
chemical and abrasion resistance”, while
being able to be applied direct to metal
in a single, high-build coat.
Performance is backed up by case
histories, built up over many years for the
full range of mining markets, giving the
user greater confidence.
New formulations are always being
developed. Valspar, for example,
continues to develop technologies to
enhance corrosion protection and recently
introduced an innovative zinc-free,
low-emission, waterborne technology
called Valspar Aquaguard coating.
It outperforms some solvent-based
coatings, based on industry test
standards, providing superior corrosion
performance through a combination of
high density, chemical adhesion and
anticorrosive properties.
Valspar Aquaguard coating is currently
being used in the shipping-container and
truck-chassis industries, and it is
expanding into other industries, including
mining, where there is demand for
high-performance corrosion coating.
This coating also provides a significant
environmental advantage to manufacturers
in that it is water-based. Valspar tells
Mining Magazine that it anticipates that
OEMs supplying the mining industry will
soon use this new coating innovation.
Mobile versus fixed
One of the most obvious differences in
approach is between mobile and fixed
equipment. Mr Bolz at Valspar explains:
“Whether the equipment is mobile,
semi-fixed or fixed, the types of coatings
typically used are epoxy or urethane
primer and urethane top coating. The
thickness at which the coating is applied
may vary based on durability needs.
“For example, it is less likely that
full-fixed equipment will make contact
with a rock or tree to damage the coating,
so that is less of a concern when choosing
a coating. For pipelines, in particular,
both internal and external coatings are a
consideration. These coatings need to
provide strong corrosion performance in
a wide variety of elements.”
Valspar makes a full line of Valspar
Pipeclad corrosion-protection coatings for
the pipeline industry. For increased
performance, additional thickness can be
added to the coating. Thicker coatings
can provide continued high performance
for up to 50 years of use.
Jon Wilson tells Mining Magazine: “This
is dependent on the design life of the asset,
but, generally, mobile mining equipment
has both the need for protection but is also
often required to be brightly coloured
with long-term aesthetics.”
On mobile equipment, International
Paint recommends an acrylic polysiloxane
as a topcoat over a robust, anti-corrosive
intermediate and premium zinc primer.
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.com
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COATINGS
23
See us at bauma China, booth E6-447
Repair and OEM painting
Whether equipment is ‘patched up’ with paint
during routine maintenance or completely
resprayed depends on the type of equipment
and the geography. For very large equipment
such as stacker reclaimers, spot repairs will be
conducted if required, but if the correct surface
preparation and coating system is selected at
the design stage then any maintenance should
be limited.
A good example of long-lasting coatings on
equipment is the bucket-wheel classifier used in
the UK kaolin (china clay) industry.
In the mid-1990s, coatings specialist Irathane
Futura supplied English China Clays (ECC, now
part of Imerys) with a solution for the numerous
bucket wheels it employs throughout its
Cornwall complex.
A variety of methods had been implemented
in the attempt to improve the operating life of
the wear surfaces, including the use of specialty
hardened steel and
the application of
hard, rubber
plates.
Semi-mobile
crusher
station,
UK
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The Irathane 155 coating (a two-part,
solvent-based, spray-applied elastomeric
polyurethane/urea) was applied to the surface of
a steel-fabricated, 6m-diameter bucket wheel at
the Melbur pit.
This machine is used in the first stage of
sand/water separation, and is therefore subject
to very demanding abrasion and corrosion. After
a successful period of use without maintenance,
the equipment is still being used with the original
coating. Irathane 155 is now specified as the
standard protective coating for all new bucket
wheels at the operations, as well as for
refurbishments of existing equipment.
Small OEM equipment is, by contrast, often
repainted completely or even replaced after a
relatively short time. Normally in the maintenance
process the equipment and structures are
completely coated after a satisfactory surface
preparation. Sand-blasting or shot-blasting are
used, as is water jetting.
Sherwin-Williams’ ES301 topcoat is used for
post-water jetting – this is a damp, surfacetolerant system, which can be applied immediately
after hydro-blasting.
Patching is deemed acceptable in the industry
when, during construction, a structure or
equipment is damaged from friction or a blow of
some sort. It is also more common to spot-repair
localised areas on mobile mining equipment.
The primary driver for this is that spot repair is
less time-consuming. This minimises equipment
and mine operation downtime, which is
important to the equipment owner’s investment.
Quick drying is always important, especially
when the construction schedule is tight or a vital
piece of equipment is being repaired. It is
therefore important to consider the long-term
performance carefully when deciding on the new
construction-coating plan to maximise the time
to first maintenance, and help the fabricator
and main contractor fit the application into
their often short schedule.
The concept ‘quick dry’ has a direct
relationship to temperature; in zones or areas
where the temperatures are low, special
hardeners may be used to enable the coating
to cure faster or at low temperatures.
In equipment manufacturing, large
components have broad surface areas to
coat, and the faster the coating dries the
faster it can move through the
process and be shipped.
Speed of application, cost and
gloss are the important factors
for equipment OEMs, whether
trucks or process equipment.
But, adds Mr Wilson at
International Paint: “It is also
important to consider the life
expectancy of the structure and
select a suitable coating system,
based on the environment and
design life. If this is done correctly
then regular repainting is not so
much of an issue.”
Duramax
®
MID-PRESSURE HYDRAULIC fILtERS
• Heavy-duty steel body
• Die-cast aluminum thread
plate for extra strength
• Multiple media choices,
including Donaldson’s
Synteq™ Media technology
• Available in 3 diameters and
multiple lengths
• Working pressures from
350 to 1000 psi
Contact Donaldson or your local
dealer/distributor for more info!
www.DonaldsonFilters.com
1.866.484.8350
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