Tower protection for longer offshore life

As wind development shifts to the seas, interest has been growing to find better solutions to protect equipment -- particularly towers -- from corrosion. A non-profit group, the Thermal Spray Society (TSS), is thus stepping up a campaign to the wind sector to promote the cost and environmental benefits of thermal spray coating. The technology -- which uses coats of aluminium, zinc or an alloy of the two metals -- is typically used to protect steel structures against corrosion from wind, salt and water. Patented around 1905 and used in the offshore oil industry, the thermal spray process can give turbine towers a lifetime of more than 25 years without maintenance, claims Tony de Munter of TSS, an affiliate of ASM International. No wind turbine companies have used the technology, preferring to use conventional tower coatings.

De Munter says thermal spray is far more environmentally friendly than traditional coating and longer lasting than organic coating. For this reason, the technology is becoming more attractive to offshore industries, particularly due to environmental regulations that are outlawing commonly used paints and epoxies.

Conventional protection for wind turbine towers costs about EUR 50 per square metre and usually consists of a layer of zinc and several epoxy layers. Its service life ranges from eight to 12 years, he says. Thermal spray coating will cost 50-100% more at first -- around EUR 75-EUR 80 -- but the difference will be recovered already from the first maintenance cycle, de Munter says.

He adds that the US Federal Highway Administration, in a seven year study of environmentally acceptable materials for the corrosion protection of steel bridges, concluded that thermal spray coatings "consistently provided the best corrosion protection performance."