Subsea Foundation & Floater Cathodic Protection (CP) Monitoring

Wind farm subsea foundations and floaters are made of welded steel plates which are shot or sand-blasted and then coated with thick, multi-layer paint systems. Surface preparation and paint application is never perfect, particularly on such big structures.

Paint tends to come-off locally due to impacts during transport and installation, but also at areas of poorer surface preparation and thinner coat application, letting raw steel exposed to seawater and resulting in local galvanic corrosion.

Galvanic corrosion is the loss of material resulting from the transfer of electrons from one material (steel in that case) to a nobler one (eg: stainless steel), through an electrolyte (seawater). To counter-act this phenomenon, some blocks of material called “sacrificial anodes” (made of even less noble material than steel) are welded at some locations on the structure, acting as a preferential source of electrons instead of steel. Anodes are progressively “eaten” instead of steel by nobler materials around. Anodes are sized to last several years in “normal” conditions, but they can quickly disappear if paint has extensively come off.

Galvanic corrosion creates electrical potentials at the surface of steel, but also in surrounding seawater. By measuring this potential, we can monitor and map the degree of galvanic corrosion and the efficiency of the cathodic protection (paint+anode). Needs for paint reapplication or anode replacement can be anticipated, avoiding extremely costly replacement or repair of the foundations.

Based on our experience of subsea CP monitoring in the oil & gas industry, we provide similar CP monitoring services for the wind energy sector using advanced subsea CP measurement tools deployed by divers or ROV.