1. Wind Turbines: Challenges Associated with Corrosion Protection

2. Learning Outcomes
At the conclusion of this webinar you will be able to:
Define the coating-specific sections
Define challenges associated with corrosion protection of wind turbines
Define wind turbine performance standards
Define corrosion protection methods for wind turbines
Define industry standards for corrosion protection of wind turbines
Define coating systems used to protect wind turbines

3. Two Wind Markets – Onshore and Offshore

4. Three Coatings Sections - Onshore
Rotor Blades 
Nacelle 
Tower 

5. Five Coatings Sections – Offshore
Rotor Blades 
Nacelle 
Tower 
Mooring 
Substructure 

6. Challenges in Corrosion Protection of a Wind Turbine
Most wind farm owners/operators are looking for a year service life on all coatings.
In general, coating manufacturers and tower fabricators may be asked to provide a joint warranty for a specific time frame

7. Challenges in Corrosion Protection of a Wind Turbine – Onshore
Wind turbines are usually placed in rural, often remote areas, making future maintenance challenging and expensive
Wind turbines can stretch hundreds of feet in the air, making accessibility difficult

8. Challenges in Corrosion Protection of a Wind Turbine – Onshore
On-Shore Wind Turbines face the following challenges:
Dew/condensation with or without salinity
Exposure to UV light
Wind blown debris
Extreme temperature ranges
130 F (54 C) to -80F (-62 C)

9. Challenges in Corrosion Protection of a Wind Turbine – Offshore
In addition to the previous challenges, off-shore wind turbines face:
Mechanical loads
Floating Ice
Biofouling in Submerged Zones
Variation in Weather Conditions
Wind and Waves

10. Rotor Blades Performance Standards
Coated rotor blades must be free of imperfections. Each surface imperfection on a wind turbine blade results in additional drag, and thus, decreases efficiency

11. Rotor Blades Performance Standards
Rotor blades flex when in use, therefore so must there protective coatings
Coatings must flex without fracturing
Coating must be able to retain adhesion to the base coat and substrate when rotor blades flex

12. Rotor Blades Performance Standards
Coatings applied to Rotor Blades must be abrasion resistant. With Rotor Blades up to 5 MW (mega watts) being installed, they are susceptible to wind blown debris

13. Nacelle Performance Standards
The nacelle must be protected from corrosion using a protective coating system
The inside must be kept clean and dry. Climate is controlled using dehumidifiers

14. Tower Section Standards
The tower consist of three sections:
Steel Tower which is protected with a coating
Sub-Structure of the tower if sub-merged in water is protected by cathodic protection in conjunction with a coating system. If on-shore just a coating system is necessary
Mooring is protected with a coating

15. Tower System Requirements
ISO deals with performance requirements for protective paint systems
Defines test methods used to determine the composition of the separate components of the paint systems
Defines laboratory performance test methods for assessing the paint systems
Defines criteria for evaluating results

16. Tower System Requirements
Typical evaluation criteria is:
Degree of blistering and cracking (ASTM D 714 or ISO 4628)
Degree of rusting (SSPC VIS 2, ASTM D 610 or ISO 4628)
Degree of chalking (ISO 4628)
Degree of flaking (ISO 4628)
Adhesion (ASTM D 4541 or ISO 4624)

17. Tower System Requirements
Creep from scribe after 4200 hours of exposure to stresses of:
UV Light
Condensation
Salt Spray
Freezing
Immersion in Sea Water (ISO 2812)
Cathodic disbonding after 4200 hours per ISO 15711

18. Tower System Requirements
ISO defines five corrosion categories:
C1 (not corrosive interior atmosphere) up to C5-I and C5M (Industrial and Marine)
Most wind farms are rural areas, C3 (Moderate Load)
According to Part 5, C3 categories should be coated with a multi-coat system with a DFT of 6-10 mils

19. Tower System Requirements
ISO12944 Part 5 defines expected time of protection for various coating systems
Low Durability
(2 to 5 years)
Medium Durability
(5 to 15 years)
High Durability
(greater than 15 years)

20. On-Shore Typical Coating Systems
Three Coating System
Epoxy Zinc-Rich Primer (2 to 4 mils)
Epoxy Intermediate Coat (4 to 6 mils)
Polyurethane Topcoat (2 to 4 mils)
High Performance Two Coat Systems
Epoxy Zinc-Rich Primer (3 to 4 mils)
Polyurethane Topcoat (4 to 5 mils)

21. Off-Shore Corrosion Protection
Standards for off-shore wind turbine protection are:
ISO 12944
NORSOK M 501

22. Off-Shore Corrosion Protection
ISO characterizes the conditions to which offshore wind turbines are exposed to as C5 M or IM 2 (immersion)
C5 M categories are non-immersed and should be coated with a multi-coat system with DFTs in the range of 12 to 20 mils
IM 2 indicates structure is immersed and should be coated with a multi-coat system with DFTs in the range of 20 to 40 mils in conjunction with cathodic protection

23. Off-Shore Corrosion Protection
NORSOK M-501 specifies similar systems
Atmospheric exposure should have a minimum DFT of 13 mils
Immersed exposure should have a minimum DFT of 18 mils

24. Typical Off-Shore Above Splashzone Coating Systems
Three Coating System
Epoxy Zinc-Rich Primer (2 to 4 mils)
Epoxy Intermediate Coating (2 Coats at 4-6 mils)
Polyurethane Topcoat (2-4 mils)

25. Typical Off-Shore Under Splashzone Coating Systems
Two Coat System
Epoxy Coating (2 coats at 8-10 mils)
NOTE- For areas under water (immersion service) NORSOK requires cathodic protection to be used in conjunction with coating system
Install impressed cathodic corrosion protection
Weld sacrificial anodes

26. Looking Ahead Self repairing coatings
Healing agents/inhibitors release from microcapsules when coating gets damaged

27. Summary
Coating wind turbines can be challenging due to the complicated design of the structure and environmental location. To assure corrosion protection, industry standards must be followed and qualified coatings applied.