Sacrificial Anodes for the external underwater cathodic protection for offshore wind turbines would typically consist of the same type of platform anodes used for submersed oil and gas support structures
Typical examples of Platform and Hull Anodes can be found here (just click on the link Below
Aluminum Platform and Hull Anodes
Another approach to using sacrificial anodes for the cathodic protection for the exterior submersed area is the use of an anode cage
Also note that any custom anode design can be manufactured by GALVOTEC
Other sacrificial anodes that would be utilized for the submersed areas of the internals of monopiles would typically be anodes that are cast on to wire rope as depicted in the image below
Galvotec has a team of engineers that can assist in any anode system design