The offshore industry has learned the hard way that the harsh offshore environment can quickly expose inadequate protective coating systems.
Future offshore wind installations will differ in many ways from those currently in place. They will be significantly larger in turbine size, up to ten times further offshore than current wind farms and located in deep water – the so called `Far shore´ projects.
This development will bring new challenges in the offshore environment – one of the most hostile natural habitats known. Any steel structure will face potentially increased corrosion rates from highly corrosive conditions, such as high levels of salt contamination, full seawater immersion, splash zones and high UV exposure.
Unprotected steel structures in the fully immersed area, and those situated above water in the atmospheric zone, corrode at four times the rate of similar structures located inland due to the prolonged wet conditions and high chloride concentrations. Rates are higher in the splash zone: up to ten times the rate for inland structures, with structures also subject to water erosion, winter ice, impact and abrasion.
Premature coating failures in the past have resulted in expensive maintenance programs to repair failing coating systems in situ. The cost of offshore maintenance is significantly higher than for similar work on land. Perform repairs in short weather windows. Surfaces require constant washing down to remove salt contamination. Also access is difficult and dangerous. Therefore, coating systems for new construction must be suitable for offshore exposure. This in order to give the desired high durability.
Internationally recognized standards
A number of internationally recognized standards, ISO 129441, ISO 203402 and NORSOK M-5013, are available to assist the specifiers. This ensures that a coating system will meet the necessary requirements. However, these standards are for guidance only. They are no substitute for the proven performance of a coating system over a long period offshore.
PPG´s offshore protective coating systems provide user-friendly application properties at new construction and proven long-term durability in service. Therefore, the systems specified for the foundations and external sections of wind turbine towers are pre-qualified to the recognized standards mentioned above. Most importantly, they are proven to work in offshore service conditions.
PPG two-coat system
For external tower sections, PPG has an innovative two-coat system. This consists of a zinc-rich epoxy followed by an extremely durable finish. This system is easy to apply in-shop. It gives fast steel throughput whilst offering excellent anti-corrosive properties and outstanding resistance to the high UV levels. Also, inorganic hybrid products such as polysiloxanes offer a major improvement in the durability and aesthetics for offshore coating systems.