Wind turbine coating: The power of protective paints
The development of wind as a reliable, sustainable, clean and commercially viable energy source has led to the need to protect the most important asset in the generation of wind energy – the wind turbine. This power generation system is made up of different components with protective coatings specialized for each specific part. There are coatings for blades, tower, bolts and magnets. Wind turbine coating is aimed at preventing damage from exposure to the elements.
Essentially, there are two main types of wind turbines; offshore and onshore wind turbines. New Zealand has 19 wind farms either operating or under construction. The windiest city in the world, Wellington, has over 100 turbines. Furthermore, as New Zealand moves into the future with wind energy a priority for utility-scale generation it is imperative to everyone involved in the production and erection of wind turbines to know the measures to take for optimum performance.
This article explores wind turbine coating in detail, products and how to preserve wind turbines for as long as possible.
Breezing through the basics of turbine coatings
In developing early coatings for turbines, the main concern was for the blade. Blades need coating because they are constantly exposed to the weather and moving in air.
Airborne sand hitting the turbine at high speeds, chemical attack from organic acids due to bug swarms, and ice accretion damages the turbine
Without coating, blades are vulnerable to extremely localized corrosion that leads to the creation of small holes in the metal.
Consequently, the surface becomes rough and unstable harmonics are created. Furthermore this decreases the turbine’s efficiency and increases maintenance and repair costs.
The active properties of the coatings include;
- Polyamine
- Aliphatic or aromatic esters
- Self-healing polymers
- Polyurethane
- Reinforced Inorganic Zinc and other anti-corrosive metals
Wind turbine coatings are, therefore, typically;-
- Icephobic – low ice adhesion strength (under 20 kilopascal) is critical to preventing ice accretion in cold climates
- High Erosion Resistant – erosion caused by airborne sand hitting the blades depreciates the lifespan of turbines
Other systems such as ice-repellent coatings are in the process of commercialization as researchers continue to innovate wind turbine coatings centred on softer coatings that are still tough, but not brittle.
Choosing the right coating for the right environment
Not every coating is suitable for application in different atmospheres. Depending on the exposure zone of wind power structures, the type of coating and number of layers will need to be considered.
Atmospheric Exposure
| COATING SYSTEM | NUMBER OF LAYERS | BENEFITS | DRAWBACKS |
|---|---|---|---|
| Vinyl system | 3-4 layers | The film properties and weathering characteristics also show good low temperature drying and intercoat adhesion characteristics | In general, vinyl resins have a high VOC content, which restricts their use in some parts of the world |
| Zn phosphate pigmented two pack epoxy primer | 1 layer | Can be incorporated into almost any binder and because of its low opacity or transparent nature, paints of any colour can be produced. | High pigmentation levels are needed to give adequate anti-corrosion protection |
| Two-pack epoxy | 2 layers | Somewhat stronger than one-part epoxies, because of their different curing characteristics | Mixing equipment and problems with incorrect ratios |
| Inorganic zinc silicate primer | 1 layer | Coatings based on these resins are very hard, corrosion resistant and temperature resistant perform well under neutral pH | Requires more application expertise, both in regard to carefully monitoring ambient atmospheric conditions to assure appropriate curing before top coating, and in applying the proper dry film thicknesses of both the inorganic zinc and the topcoats |
| Chlorinated rubber system | 3-4 layers | Will dry at low temperatures and give good intercoat adhesion in both freshly applied and aged systems, making them suitable for maintenance purposes | Temperature sensitivity can lead to various film defects when used in very hot climates. In addition, white and pale colours have a pronounced tendency to yellow when exposed to bright sunlight |
Underwater
The main control is cathodic protection. Therefore, the use of coating systems is optional, generally epoxy-based coatings, and these should be compatible with the cathodic protection. However, the use of coatings leads to fewer anodes being needed in the cathodic protection process and longer lasting corrosion protection.
Splash and Tidal Zones
The same coatings as the atmospheric zone are suitable. However, the film thickness is increased
- Thick rubber or neoprene coating up to 15 mm of thickness.
- Polymeric resins or glass-flake reinforced polyester material are often used to protect against mechanical damage
3 Steps to wind turbine blade coating in New Zealand
Repairing the coating of structures can be very difficult and expensive. Following adequate preparation steps can lead to significant cost savings. We have made 3 steps to set you on your way to getting the best protection for wind turbines.
Step 1: Determine what kind of wind turbine you want to coat
Although logical, it is important to realize that the procedures for coating an offshore wind turbine will differ in complexity to coating an onshore structure. The most prominent complexity is in application method. Coating application can be done either in factory or on-site. For offshore wind turbines, factory application allows superior control of conditions and waste and pollution management. However, the risk of damage during handling, transport and erection differs for both types of wind turbines.
Step 2: Seek specialist information
Always look for a specialist with experience in your sector. This allows an objective cost benefit analysis for your coating project as well as regulative advice, particularly with environmental implications of wind turbine coating. We have an extensive network with experienced specialists from various industries and are happy to put you in touch without any obligation.
Step 3: Request a quote
Although New Zealand’s reputation for DIY is renowned, the best results are achieved by applying wind turbine coating through a recognized specialist. Specialists can survey the condition of the structure and provide competent service, all of which can be evaluated by requesting quotes. Below is an overview of companies that offer professional wind turbine maintenance. Of course we are happy to help you select the specialist that best suits your project.
| WIND TURBINE COATING SPECIALIST | ADDRESS | SPECIALIZATION | APPLICATION |
|---|---|---|---|
| TBS Group | 2 Morningside Drive, Morningside, Auckland 1025 | Wind farm turbine maintenance | Yes |
| Goleman Ltd | 24A Allright Pl, Mount Wellington, Auckland 1060 | Wind farm construction and maintenance | Yes |
| SGS New Zealand Limited | SGS House, Level 4, 8 Rockridge Avenue, Penrose, Onehunga, Auckland 1061 | Coating inspection and failure analysis | No |
| Technical Rigging Services NZ Ltd | 44B Greenpark Road, Penrose, Auckland 1061 | Erection, inspections and maintenance | Yes |
| AH Gears | 9 Beasley Ave, Penrose, Auckland 1061 | Up-tower maintenance and inspection on existing gearboxes | On gearbox |
| Ashhurst Engineering & Construction Co. (1989) Ltd | 83/87 York St, Kelvin Grove, Ashhurst 4810 | Wind farm maintenance | Yes |
For the specialist in need of wind turbine coating market products in New Zealand
AkzoNobel International is the global leader in the supply of coatings for wind turbines. In total, the company manufactures 105 specialized products for this sector of protective paints. PPG is also active in New Zealand with 12 products applicable to the tower, nacelle and blade.
The following is a list of the most popular products in New Zealand
| MANUFACTURER | PRODUCT NAME | DESCRIPTION | APPLIED TO |
|---|---|---|---|
| AkzoNobel International | Interthane® 990 | A two component acrylic polyurethane finish giving excellent durability and long term recoatability | Tower, blades, shaft |
| AkzoNobel International | Interzone® 954 | A two component, low VOC, high solids, modified epoxy barrier coat designed to give long term protection in a single coat application. Will continue to cure when immersed in water and has excellent cathodic disbondment resistance | Subsea tower |
| PPG Protective and Marine Coatings | Amercoat® 370 | Two component, fast dry multi-purpose epoxy coating | Subsea tower |
| PPG Protective and Marine Coatings | Amerlock® 400 GF / SigmaShield 400 | Two-component, high solids glass flake reinforced polyamine cured epoxy coating | Tower, blades, shaft |
| Hempel | Hempadur® AvantGuard 750 | Two-component, activated zinc-rich epoxy primer for long-term protection of steel in severely corrosive environments | Tower, blades, shaft |
| Hempel | Hempadur Mastic® 45880 | Two-component polyamide adduct cured, high solids, high build epoxy paint. | Subsea tower |
