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deal with sewer flows, groundwater leaks, contaminated
substrate, insects, animals, traffic, dangerous gasses and
so on.
Less-than-ideal environmental conditions are also a
challenge in properly applying concrete coatings and
affect their long-term performance. Rain, heat, cold,
humidity and extremely dry conditions make it difficult to
apply coatings on the porous surface of concrete. Increases
in surface temperature during the initial coat to bare concrete
may cause expansion of air and solvent within the
concrete surface resulting in pinholes and bubbling as
they escape through the uncured film. Concrete moisture
can also cause a substrate side amine blush that is concealed
from routine inspection and later results in osmotic
blistering in immersion service. Many times the applicator
will start with acceptable conditions and changes
occur throughout the day that may cause the work to be
ruined, or questionable at the very least.
Field conditions must be continuously monitored to
understand and adjust for their potential effects on the
coating system being installed. Often, it is beneficial to
control the environment to the extent possible using techniques
such as containment, temperature control and
dehumidification.
Qualification of Applicators
Even the very best coating system will fail if not properly
installed. Similar to product selection and specification
writing, the use of a qualified applicator is a critical
element of a successful coatings project. Inexperienced
buyers often sort “painting contractors” into one single
group. In reality, coating application typically involves
very specialized processes and equipment, and the most
qualified applicators are often the ones that specialize in
a particular area, such as concrete tank linings, manhole
coatings, floor coatings or structural steel.
Specialization fosters the development of best practices,
work efficiency and improved product quality. When
the same processes are repeated, mistakes are usually
reduced or eliminated, and the process can be continuously
improved. Risks are reduced and the odds of success
are increased. In contrast, using inexperienced applicators
predictably results in a large learning curve. With
complex coating and lining systems, this learning curve
can be very costly.
The best contractor on the last job might not be the best
for the next job if the type of coating work to be performed
is significantly different than the last time. The applicator’s
area of expertise should be a prime consideration
when developing a short list of bidders for a project.
A good source to find qualified applicators is the
manufacturer of the selected products. Generally, they
will want to recommend qualified applicators to better
ensure the success of their product. Some manufacturers
of high-performance coatings only sell to contractors
that have gone through some form of a manufacturer
training and qualification program to become an
“approved” applicator. Requiring the contactor to be a
manufacturer-approved applicator is almost always a
good idea. Proof of approval should always be in writing
from the manufacturer.
References and referrals from other past projects
should always be required and fully investigated in the
applicator selection process. To ensure the “low-bid” is
meaningful, final consideration of bidders should be limited
to only those that are truly qualified to perform the
work. Otherwise, an apparent lower price may only be
due to a lack of understanding of the project requirements.
Accepting an inappropriately low bid from an
inexperienced applicator contractor will predictably
result in unsatisfactory results as well as change orders,
schedule delays and excessive rework.
In-Process Inspection
Some coatings applicators do excellent work. Some do
not. However, if an applicator knows that all of its work
will be inspected thoroughly, it is far more likely to do a
good job. Full-time, in-process quality control inspection
helps ensure that the selected coating system is properly
implemented.
Although the utility owner should monitor and inspect
the quality of the work, the applicator must be ultimately
responsible for its performance, quality control and
workmanship. In cases where the owner assigns an
inspector, the applicator will often attempt to use the
inspector as a gauge for its work. If problems arise, the
applicator often responds by saying it was doing what it
was told and it passed all inspections, suggesting it is not
the problem of the applicator. This undesirable scenario
blurs lines of responsibility because the owner’s inspector
has inadvertently become part of the applicator’s
work process. The system specifier must make it clear in
the project procurement documents that the owner
reserves the right to inspect, but has no burden or
responsibility for the final outcome. It must be clear that
quality control is the sole responsibility of the contractor.
It is ideal for every coatings applicator to have its
own qualified, full-time inspector working at all times
during the installation process.
Even when an applicator has a qualified inspector, it
can still be difficult to always get quality workmanship.
The inspector’s paycheck comes from the applicator,
which sometimes makes it difficult to perform inspections
and report in an effective and unbiased manner. For this
reason, on larger or complex projects, it is usually advisable
for the owner to hire a qualified NACE-certified
coating inspector to monitor the work to ensure project
requirements are being followed. This added oversight
usually enables the applicator’s inspector to do a better
job. However, as previously noted, the owner’s assignment
of an inspector should never replace the requirement
for the applicator to inspect its own work.
Another useful tool to ensure project quality is to
require that the applicator utilize a manufacturer’s technical
representative to provide field training and verify
on a continuous basis that work is being completed in
accordance with the manufacturer’s requirements. The
manufacturer should inspect storage, surface preparation,
mixing, application, testing and should ultimately
provide some form of a Certificate of Proper Installation.
After all, the manufacturer is the expert with its material
and is in the best position to resolve unexpected challenges
that develop in the field.
To the uniformed, this level of oversight and precaution
might seem a little overboard. However, due to their cost
and complexity, coatings and linings in wastewater environments
have demonstrated an unusually high rate of
failure compared with most other construction activities.
38 Water Utility Infrastructure Management
November/December 2011