Corrosion protection at offshore wind farms could lead to increased concentrations of metals in seawater and seabed. This was announced by the Federal Maritime and Hydrographic Agency and the Helmholtz Center Hereon in a joint press release. A research team examined water and soil samples from the vicinity of wind turbines in the North Sea. The concentrations determined were largely within the known variability for the North Sea. However, isolated increased concentrations of aluminum, zinc, indium and gallium were noticed. In addition, some of the sediment contained locally increased concentrations of lead. So far, however, no direct effects on the marine environment have been identified, the Federal Office said.
The occasional increase in values could possibly be due to certain weather conditions in which the water around the offshore installations was only minimally mixed. The causes of the locally increased lead concentrations have not yet been clearly identified.
The metals are used in galvanic anodes, the sacrificial anodes that prevent corrosion of offshore steel structures. In doing so, however, they dissolve themselves. Indium and gallium are rarely found naturally in the sea. They are therefore regarded as tracers that reveal the origin of the emissions from the sacrificial anodes. According to the press release, 150 to 750 kilograms of anode material are currently released into the marine environment per year and wind turbine.
According to the Federal Office, more than 1,500 wind turbines are already in operation in the North and Baltic Seas, and there are also 30 transformer and converter platforms off the German coast. The Federal Office fears that the further expansion of wind energy at sea could increase emissions from corrosion protection. In the future, wind farm operators should therefore increasingly use external current anodes that only release very small amounts of substances into the marine environment.