Surface World September 2019 Surface World September 2019 | Page 60
PAINT & POWDER
How Many Mils is Your Coating?
Instantaneous handheld coating thickness gauges that can
be operated by virtually any technician deliver lab-quality
readings even on curved and complex surfaces
From the job shop to
the robotic assembly
floor, it is vital that the
product be made well
and correctly coated for
protection, aesthetics,
and performance.
So, industries like automotive, aerospace,
and those utilising plating, anodising,
powder coating or other coatings need
accurate coating thickness measurement.
This is particularly important when the
coatings play a critical role in preventing
the corrosion or wear of metal substrates.
Properly applied coatings, with thickness
measured in mils (.001 inch) or microns
(.001 mm), are also essential for paint/
coatings contractors and companies
that coat a wide range of building and
functional surfaces, including pipe.
Accurate application and coating thickness
measurement, in fact, are crucial to avoid
coating breaches leading to corrosion
of the underlying substrate. This can help
to prevent leaks and other safety issues
in a wide range of industries.
However, until recently conducting frequent
laboratory-quality coating thickness tests
throughout the manufacturing process or
in the field has been difficult. Traditionally,
this required meticulous sampling and
preparation, as well as taking the sample
to the lab for evaluation. Although portable
coating thickness gauges are not new,
most fail to provide the accuracy, speed,
or simplicity required for anyone to conduct
quick checks as needed on the production
line or in the field.
Fortunately, handheld devices are now
available that allow personnel to easily and
quickly perform lab-quality coating thickness
measurements. Some options offer instant
coating thickness measurement of almost
any non-magnetic coating on both ferrous
(magnetic) and non-ferrous (non-magnetic)
substrates. This is possible using only one
58
hand, even on curved and complex surfaces.
By simplifying the process, industrial
facilities and paint/coatings contractors
and companies can increase the quality
of their products and services from start
to finish while optimising cost.
The Many Benefits of
Coating Thickness Readings
Coating thickness directly affects product
quality, whether for automotive paint,
electroplating, anodising, or a wide range
of other coating applications. For example,
checking the paint coating consistency
on a vehicle not only provides a product
with a superior finish, but can also offer
essential data about the consistency of the
paint when it is wet.
“Incorrect paint consistency can affect drying
times or eventual flaking of the paint film,”
says John Bogart, Managing Director of Kett
US, a manufacturer of a full range of coating
thickness testers. “Too little paint coating and
you are left with cosmetic issues in opacity,
and protective issues like corrosion, wear,
and exposure. Checking coating thickness
can also tell if auto body work has been
done on a used car, which can help the
customer or dealer make a good decision
on pricing.”
When specificity and adhesion matter in
anodizing and electroplating, a coating
thickness gauge should be able to read the
thickness of the coating to the most minute
measurement. This can play a major factor
in preventing corrosion while optimizing the
process by eliminating any excess use of
the expensive plating product.
“This might involve petrochemical pipes
in a facility, water pipes in a home or office,
or even the piping and tubing in an engine.”
“A nondestructive gauge is a perfect way
to ensure that the pipe’s protective coating
has not been applied too thinly or become
so over time,” he adds. “Excessively thin
coatings are more likely to be chipped
or breached, which can lead to corrosion
promoters like water or oxygen getting under
the coating and accelerating corrosion in
the substrate.”
Simplifying Coating
Thickness Measurement
Although traditional laboratory and online
based coating thickness measurement
techniques are useful in the right settings,
they have lacked the simplicity and flexibility
required for frequent spot checks. Often, this
involves sampling, sample preparation, and
taking the sample to the lab for evaluation,
which requires the participation of staff
adequately trained for the process.
Other conventional coating tests, such as
scratch testing, have been destructive or
invasive and damaged the sample. This
meant that a product could not be returned
to the production line, or that a coated
surface had to be recoated or repaired in
the field at additional expense. Also, since
only a small portion of the component or
facility may be tested, results may not be
representative of the entire situation.
Consequently, various portable coating
thickness measurement devices have been
developed. However, these have not always
provided the necessary accuracy or been
sufficiently easy to use.
Another way a coating thickness gauge
can make a significant impact is in testing
anti-corrosion pipe coatings to find weak
spots, where the coating is too thin and
a breach of the coating could make the
substrate susceptible to corrosion,
according to Bogart. Another drawback is that in certain
environments with multiple substrates,
the devices typically either had difficulty
determining the substrate or utilising the
correct test for the application. So, multiple
measurement devices had to be used, which
complicated testing and added cost.
“Knowing about these trouble spots can
prevent a disaster well before it occurs,”
he says. Finally, typical coating measurement methods
were usually unable to accurately measure
curved or complex surfaces. This left pipe as
SEPTEMBER 2019
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