Protecting Wind Turbine Towers

Date:December 2016
Capability:   Cathodic Protection
Location:United States
cathodic protection

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.


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