Wind turbine towers can be found all over the globe. As with
all steel structures exposed to the elements, corrosion will
eventually take over and degrade the structural integrity of the
tower if no protective coatings are applied to form a barrier
between the steel structure and moisture. Aegion’s Corrosion
Protection platform’s coatings inspection group was onsite to
inspect the complete removal of existing coatings on the exterior
of a 178-foot-tall turbine tower and perform spot repairs on
the inside of the tower. The tower is owned by a wastewater
treatment plant that uses the generated electricity to help power
the facility. The owner of the tower realized the added benefit of
having an Aegion NACE certified coatings inspector onsite each
day to ensure all aspects of the project were carried out by the
contractor according to the specification. The added cost of an
onsite NACE certified coatings inspector was minimal.
The tower consists of a concrete foundation with three separate
sections that were hoisted by crane and bolted together on the
inside of the structure. The structure has a tapered shape, with a
13-foot inside diameter at the base and an 8-foot inside diameter
at the top. To access the entire exterior, scaffolding was installed
from the ground to the top of the tower. A containment system
was then installed around the scaffolding, forming a sealed work
area to prevent any paint chips and other debris from escaping
the work area during abrasive blasting. This process also
removed the old coatings and rust. The scaffold and containment
structure was engineered and designed with specific wind load
ratings to both ensure the safety of the workers and prevent
more stress on the tower than it was designed to tolerate.
The scope of work consisted of the following:
- Blast clean the outer surface according to
SSPC-SP10/NACE No. 2
- Near white blast cleaning followed by a zinc-rich epoxy primer
- Epoxy stripe coat to all welds and connection seams
- Full epoxy intermediate coat
- Full polyurethane topcoat
The interior of the structure also needed repairs in many locations.
The interior of the structure had multiple cables and an array of
electronic equipment inside. This required using vacuum-shrouded
power tool cleaning to repair this area. Wrapping of all electronic
components in plastic was also needed to protect the equipment
from paint chips and other debris prior to cleaning and painting.
Two coats of the same epoxy used on the exterior were applied
to the interior. The blasting work prior to applying this coating
started at the top of the tower. At the end of each blasting day,
the primer was spray applied to all cleaned surfaces to ensure
no flash rusting occurred overnight. It took several days to
complete the blasting and priming work. The stripe coat was
then completed by brush and roller, ensuring the product was
worked into the segment seams as well as on the weld seams.
Finally, the full epoxy and polyurethane coats were spray applied,
resulting in a smooth and shiny appearance.
Every step of the process was documented by Aegion’s NACE
certified inspector. This includes measuring the thickness of each
coat applied and making sure any rework was completed prior
to the next step. All inspection reports, as well as photographs
taken, were included in a project binder and given to the owner
at the end of the project. It is expected that this coatings rehab
project will extend the life of this tower for at least 30 years.