Research highlights potentially huge cost savings from new approaches to corrosion

Tackling corrosion and developing new materials for the offshore wind and marine renewable sectors could provide massive cost savings for developers and create supply chain opportunities, according to two new reports

Commissioned by the North Sea Solutions for Innovation in Corrosion for Energy (NeSSIE) project, the reports investigated the economic potential of anticorrosion solutions and the development of new materials in the offshore renewables market.

The aim of the NeSSIE project is to tap into the existing knowledge of anti-corrosion technology and novel materials solutions in the supply chain in the maritime sector to develop demonstration projects for offshore renewables in the North Sea. The corrosion solutions, when developed and commercialised, will provide global growth and job creation opportunities in remote regions in the EU.

Among the most important objectives is to develop three offshore renewables demonstration projects relating to corrosion issues by drawing on existing maritime supply chain expertise, accelerate the deployment and cost reduction of wave, tidal and offshore wind devices and support the demonstration project developed to access public and private investment. The reports are NeSSIE Report 2.1: State of the Art Study on Materials and Solutions against Corrosion in Offshore Structures, and NeSSIE Report 2.2: Assessment of Economic Opportunity.

Four key supply chains were identified and examined in the reports: protective layers including environmentally benign paints, sprays and coatings; cathodic protection; new materials and their associated fabrication, manufacturing and assembly processes; and corrosion monitoring, assessment and repair services.

To calculate the economic worth of anti-corrosion solutions to developers and vendors, several assumptions taken from the oil and gas, maritime and offshore renewables sectors were made. Ccapex, opex and performance impacts of applying corrosion solutions were calculated separately for new materials and their associated processes, and direct corrosion solutions such as cathodic protection or coating systems. The calculations covered the UK and wider EU, and utilised projected capacity taken from various renewables roadmaps. The scenarios investigated ranged from the reduction of offshore renewables project capex to increased capex with the application of novel anticorrosion solutions, yet in all cases considered the reduction of opex and contribution towards maintaining device performance.

Corrosion is an important concern for offshore energy developers. All marine structures face corrosion problems impacting on the operations and maintenance (O&M) costs along the global lifecycle. In the case of offshore windfarms, overall O&M costs are typically around 15-30% of total lifecycle costs, and corrosion plays a significant role in these costs.

The reports found that based on offshore renewable deployment estimations, anti-corrosion solutions and new materials could see potential developers saving over €16Bn (US$19Bn) for wave and tidal energy projects in the EU by 2050 and potentially over €68Bn for offshore wind projects.

For the anti-corrosion supply chain, the wave and tidal energy markets could lead to over €25Bn of projects in the wider EU by 2050 and over €57Bn for offshore wind projects.

Scottish Enterprise team leader for energy and clean technology Jan Reid said the early work conducted by the NeSSIE project was really encouraging. “We can see there is a tremendous economic prize for the EU offshore supply chain in tackling this challenge and supporting the EU to decarbonise the energy sector,” she said. “The key to unlocking this opportunity is developing investable demonstration projects that will prove the technological solutions.”

NeSSIE project manager Stefano Valentini, who led the study, said “It is clear from this early work that there are a wide range of technical solutions that can be deployed to great effect in the offshore renewables sector. The EU supply chain is at the forefront of subsea excellence and we are confident this will bring forth excellent solutions that will see the cost of energy coming down in offshore renewables.”

The reports contribute to NeSSIE’s overall objective of developing three investable demonstration projects in offshore renewables focused on corrosion and materials. The projects will utilise the existing EU subsea supply chain and their knowledge to develop commercial solutions.

The main conclusions that can be drawn from the report are:

• Offshore renewables are estimated to play a major role, driven by both political and economic factors. The renewables-based electricity generation is projected to triple between 2013 and 2040, overtaking coal to become the largest source of electricity. According to the new policies scenario, 33% of the world electricity generation by source will come from renewables in 2040 (IEA, 2014).
• Offshore structures in general are subjected to several damage mechanisms including corrosion and fatigue; so protective strategies should be considered essential to reach the expected service life for which a structure was designed. Different protection systems can be used to delay and mitigate corrosion initiation and its related consequences such as safety, structural integrity and service life.
• Cleaning of substrates before coating is still a very fundamental operation as it strongly influences the adhesion of the protective layers and coatings on the substrate. Grinding and blasting is mostly performed but other methods like high pressure waterjets can be used.
• Modern offshore structures are increasingly made of special alloys including high strength steel, stainless steel, aluminium and even titanium alloys. Unalloyed steel, however, must always be protected because of its low corrosion resistance to the marine atmosphere. The best results are obtained by thick thermal spray aluminium or zinc aluminium coatings with or without additional paint layers. Smaller parts can be made of uncoated special stainless steels, nickel alloys etc. The number of innovative corrosion-resistant alloys however is restricted: only AMLoCor, a new, corrosion-resistant steel developed especially for marine applications was found to be a new alloy for offshore applications.
• A survey of the main standards and guidelines is required to collect all references for the materials and procedures that can be used in offshore systems.

Modelling replenishment could enhance turbine lifespan

Deltares in the Netherlands has developed a tool to model water replenishment in the foundations for offshore wind turbines and assess the performance of anti-corrosion systems. It said that by linking realistic metocean conditions with water quality processes, it can help with the optimisation of the number, positioning and size of water replenishment holes in monopile foundations.

Replenishment holes are needed to prevent acidification of stagnant water, which can cause damage to sensitive cables and other fittings inside the monopile. Acidification is caused by the chemical reactions of impressed current cathodic protection (ICCP) systems used to prevent corrosion of monopiles in offshore windfarms. More and more ICCP systems are being used in offshore wind to prevent corrosion.

In recent years there has been an increased awareness of the risk of corrosion inside monopiles. This awareness is mainly stimulated by decisions and decommissioning of existing foundations, where more corrosion than expected was observed. This has led to the installation of anticorrosion systems.

The newly-developed tool couples a hydrodynamic model with DELWAQ, a water quality model. It allows Deltares to determine pressures and wave action inside a monopile, the effect of marine growth, flow velocities through replenishment holes and pH levels in the monopile.

This information can then be used to optimise the positioning and the size of replenishment holes. The hydrodynamic flow model has been validated with physical model experiments performed in Deltares’ wave and current physical model facility.