In Search of Effective Corrosion Protection:

Cathodic Protection and Coating

Report

-------------------------------------------------------------------------------------------------------------------

----------

IQPC GmbH | Friedrichstr. 94 | D-10117 Berlin, Germany

t: +49 (0) 30 2091 3 274 | f: +49 (0) 30 2091 3240 | e: eq@iqpc.de | w: www.iqpc.de

Visit IQPC for a portfolio of topic-related events, congresses, seminars and conferences: www.iqpc.de

Despite being one of the top failure mechanisms for offshore wind structures,

corrosion has not received adequate industry attention until recently, when it has

become apparent the actual corrosive conditions of offshore wind structures can be

very different from original design specifications.

Monopile foundations, presumed to be water and airtight have been often penetrated by

oxygen and seawater, which has led to changes in environment accelerating the corrosion

processes. Corrosion problems, however, are not limited to the foundations. Driving branch,

turbine house, pneumatic system, supporting structure, control devices access technique are

all affected and require protection and monitoring.

The most effective protection can be achieved through the combined use of a high quality

coating and a cathodic protection system.

The challenges of cathodic protection

Cathodic protection (CP) has been widely used as a primary technology to protect offshore

wind structures against corrosion. Current industry standards require external surfaces of

the submerged zones to have cathodic protection, while using CP inside the structures is

optional. In the splash zone, CP is presumed to be fully protective below Mean Water Level

(MWL).

Generally, there are two categories of CP systems applied: the sacrificial anode protection

system (SACP), which uses galvanic materials (Zn or AL alloys) and is attached directly to

structure and the impressed current cathodic protection (ICCP) system, in which anodes are

made of noble materials, such as titanium, and isolated from structures (connected through

power unit). In most projects CP is performed by galvanic anodes placed solely on the TP,

but impressed current CP systems are also applicable in a growing number of projects. Both

systems have their challenges, such as requiring regular monitoring and maintenance.

Close fitted (attached directly to structure) ICCP systems are currently used by some

operators. These systems, however, can cause overprotection close to anodes in order to

achieve protection at mudline. Over protection of the foundation plies can lead to hydrogen

embritlement (HE) and hydrogen induced cracking (HIC), which can result in catastrophic

failure.

Semi-remote SACP solutions provide improved current distribution and can be suspended

from TP. They are often used in retrofits schemes. These systems have been commonly used

in oil & gas sector and represent a proven technology.