The MAREWIND project as leader towards a more sustainable and circular offshore wind sector

During the last months, the MAREWIND project has made great strides towards the validation of the developed samples. At present, the natural step is the validation in a real environment where formal controlled testing will be performed to ensure that the materials developed satisfy the expected requirements.

The consortium has started the work in real exposure and also with samples with real materials and morphologies, enabling relevant validation.

On the one hand, for bigger pieces, TECNAN has defined key parameters – such as flow rate, speed or distance – of spray gun application, and characterised the resulting samples with the aim to compare its properties versus the ones previously validated in the laboratory. Several application tests were carried out in order to adapt the procedure to complex and more realistic morphologies. More in detail, real pieces of mooring lines and inter array cables have been coated with the antifouling solution via spray gun, maintaining all the expected repellence properties, as in previous tests. The anticorrosion coating was also applied on samples around 1m2 and with curved and complex geometries with no imperfections observed. Besides, TECNAN has optimised strategies for removing the excess of product and curing conditions for real fastening elements regarding dip-coating application.

 On the other hand, TWI for its side is improving the application of the superhydrophobic coating for blades for improved control and for having higher resistance to mechanical impact.

Additionally, as advanced concrete-based materials concerned, ACCIONA has made preliminary UHPC floating prototypes, focused on the relevant scale prototype design that will be tested in more realistic environments such as wave basin for offshore application studies (EUMER facilities), at the same time, real exposure durability testing will be performed at ACCIONA Habour demo-site. Furthermore, for the Alkali Activated Concretes (AAC), CETMA carried out a small-scale prototype with a complex geometry to evaluate the ability of the AAC to flow within the mould. They have also designed the final prototype indicating the number and position of SMART reinforcing rebars.

Advances concerning the blade prototype, imply that EIRE has been working on the validation demonstrator, testing the 5m wind blade spar box, as representative section of the main structural component of the 13 m blade.

Figure 1. Bigger and real samples: real fastening elements coated with anticorrosion protection or non-coated, samples of real structures being coated with antifouling and new concretes developed.

As part of the validation activities, final optimisations of the selected formulations are being carried out in order to maximise the properties of the novel solutions developed.

More in detail, TWI has started the optimisation of the best performing coating formulation, working on the 3rd generation of antierosion coatings adjustment. After several tests, TWI has adjusted the level of functionalized microparticles in the formulation, showing an increased wear resistance of the coating.  For the reinforced composites formulations for blades, the contemplated strategies by TWI and CETMA, are progressing properly. Respecting the work of TWI, the final material test campaign for GF/epoxy-SiO2 as the new blade material was completed. The results are compared with conventional GF/epoxy, showing that the modified epoxy-SiO2 resin outperforms the conventional epoxy resin in the majority of property tests. CETMA for its side, is working on the infusion process of the TPR (thermoplastic reactive resin), as a new recyclable resins. The results of testing campaign for GF/TPR as the new blade material, has showed that properties of recyclable composite are  comparable with conventional GF/epoxy laminates. They have defined the final composition, layup and geometry of the full TPR demonstrator, and as regards TPR matrix, CETMA has selected a specific recyclable resin to be used in scale up activities with low exothermic properties to produce large parts with thick sections.

Figure 2. Fine-tuning of reinforced composite materials.

The scale-up of formulations includes the progress regarding liquid nanocoating production as well as novel concrete or composite fabrication.

On the one hand, production of the anticorrosion and antifouling coatings started with first batches of 20 liters with suitable results, having the focus on the 100 liters target of production. The spray gun application and the monitorization of the key parameters (viscosity, particle size…) showed that the larger batches have the same tendency as the product made at laboratory scale. As a result, TECNAN will produce larger batches following the same parameters. In addition, INL is producing the self-healing active material for the anticorrosion system, and studying what is the most suitable format for the scalability.

Also, the preparation of pilot batches of SiO2 mixed with epoxy infusion resin (epoxy-SiO2) has already started by TWI side, in order to supply EIRE for the production of the new blade reinforced composites

Figure 3. 20L reactor of antifouling coating and EIRE-epoxy demonstrator webs.

After having performed all laboratory tests, the MAREWIND project is currently gradually moving to a real environment.

Currently, TECNAN is testing the bigger pieces in saline mist chamber before preparing the ones to be exposed to real conditions.  Specific and bigger samples coated with the anticorrosion system are envisaged to be tested by ENEROCEAN in the upcoming months in real marine environment using TECNALIA’s HarshLab floating laboratory. On the other hand, ENEROCEAN is currently testing the antifouling coatings on flat panels, both partially submerged and in total immersion, as well as on real samples (moorings and cables) in real marine environment. These antifouling coatings tests are being performed at the Oceanic Platform of the Canary Islands (PLOCAN) facilities.

Figure 4. Real Samples with antifouling coating in real exposure tests located in PLOCAN, floating design of UHPC structure validation for the manufacturing of the relevant scale prototype for its testing in the wave basin at EUMER facilities and real environment durability testing of UHPC at ACCIONA Harbour demosite.
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On 16th and 17th November, the MAREWIND consortium met in the headquarters of Lurederra Centro Tecnológico in Los Arcos (Navarra, Spain) to discuss the 2-year progress of the project.

The first day, the meeting started with the review of the work done and the achievements reached so far on the activities related to the predictive modelling and the SHM tools for preventive maintenance of wind energy. The discussion continued with the latest updates on the technology validation and the manufacturing activities performed during the last months, including upscaling of nanocoating formulations, the generation of floating concrete prototypes and advanced composite testing among others. To wrap the first day of the meeting, the last topic addressed the preparatory actions for the future demonstration of the technologies in relevant environments.

The second day was dedicated to the presentation of the upcoming steps in the technical validation of the results such as the baseline for LCA analysis. Then, the meeting followed by a summary of all the communication and dissemination results achieved from the beginning of the project. To conclude the meeting, the consortium presented the next steps which will be followed to face the upcoming exploitation and standardisation challenges.

 Next steps

The consortium is preparing its fourth newsletter. Stay tuned for more details about the progress achieved so far.

You can subscribe for the latest MAREWIND news and events, here.


During the first 18 months of the project, the main effort has been focused on the design of high, ultrahigh performance concrete and Alkali Activated concretes that fulfil offshore infrastructures requirements. In addition, EDF has performed tests to evaluate the durability of concrete under exposure to the real environment through aging tests. It also provided support on floating offshore concrete structures, including contribution on modeling of the structures that will be used to design the prototypes to be tested.

High and ultra-high Concrete material

The reference material (Class C60 concrete) was defined from a previous experience on offshore concrete design. The work was focused on new advanced concrete materials design. After preliminary laboratory trials for the optimal raw material selection, the proper combinations were selected for high and ultra-high concrete mixtures design.

To fulfil the high performance concrete requirement, 9 dosages were casted and tested. Thedesign and optimization of the ultra-high concrete was more challenging compared to HPC, due to the occluded air that remained in the samples in the casting process.

According to the standard recommendations, HPC has low potential for cracking under restrained conditions; UHPC with PVA fibres has moderate-low potential, UHPC without SAP (super absorbent polymer) additive has moderate-high potential, UHPC with SAP additive and conventional concrete have high potential for cracking under restrained conditions. Thanks to the higher content of SCM in UHPC samples, the heat of hydration of these mixes in lower than for HPC. Therefore, showing very promising results for the advanced concrete materials developed within this task.

Semi adiabatic box equipment (left) and concrete's temperature development curve (right)
Figure 1. Semi adiabatic box equipment (left) and concrete’s temperature development curve (right).

Alkali Activated concrete

CETMA has focused on the development of alkaline activated conglomerates (AAC), considering only alkaline activators, glass powders and blast furnace slag were used as binder.

Since alkaline activated materials have a very viscous behaviour and generally have very fast setting times, they are hard materials to mix. To avoid excessive consumption of materials and safeguard equipment, the experimental program was divided into three different phases:

  • First phase: the behaviour in the fresh and hardened state of the binder composed of glass powders, blast furnace slags and activators such as water, sodium silicate and sodium hydroxide were characterized.

  • Second phase: previously optimized binder was mixed with four different types of sand for the realization and characterization of alkali activated mortars.

  • Third phase: based on previously characterized binder and mortars, AAC mix design containing three different types of aggregates was carried out.

To increase AAC mix sustainability, optimized binder-recycled aggregates compatibility was studied. Furthermore, very fine natural magnetite was used to increase the density and try to reduce the cracking phenomena caused by the heat of hydration. After choosing the best performing mix design to achieve project specifications in terms of compressive strength, consistency and workability, a final proportion optimization and repeatability study was performed.

Air content test, slump test and samples for compression tests
Figure 2.  Air content test, slump test and samples for compression tests (Left to right).

MAREWIND concretes durability characterization

For durability characterization of new concrete materials developed in MAREWIND project, several tests were carried out. Test results show that advanced concretes, as it was expected, are able to achieve better durability performance than standard C60 offshore concrete . Both advanced concretes showed in general, the same durability results, only in corrosion rate and probability UHPC presents a slight risk. Despite these slight differences, UHPC will be used on the prototype manufacturing due to its SCC behavior, that allows slender structures more suitable to keep floating structure’s buoyancy.

AAC presented similar behavior as C60 concrete in chloride penetration resistance, it showed better performance at early-ages to water penetration, whereas it seemed to be likely to develop corrosion risk during it service life. A deeper analysis will be carried out when all the ages results will be available, to check if this tendency keeps in time or not.

Durability tests water penetration, chloride intrusion, resistivity measurements (AASHTO T358)
Figure 3. Durability tests: water penetration, chloride intrusion, resistivity measurements (AASHTO T358) (From left to right) .

Durability of concrete samples exposed to a real environment

EDF performed the reference characterization of the durability properties of an ordinary offshore concrete mixture in their offshore facilities.

Chloride ingress in permanent immersion and tidal zone exposure is characterized in ϕ16×32 cm cylindrical specimens. Each sample has been divided into 3 sub-specimens of ϕ16×10 cm. The obtained sub-specimens have been subjected to chloride ingress. A first group was immersed completely in seawater, whereas, a second group was subjected to wetting/drying cycles with 6 hours period using a hydraulic pump.

As result, a comprehensive database of chloride content distribution was set up. Some basic processing including the determination of the chloride apparent diffusivity and the prediction of chlorides content evolution over time were performed.

Reinforced composites production and testing

The project plan outlines three strategies for new composite formulation:

  • the use of nano-SiO2
  • the use of Vitrimers/TPR recyclable resins
  • the use of RCF

EIRE defined a preliminary material test matrix that is being used to test the initial epoxy-SiO2 resin formulations, developed by TWI, reinforced with glass fibre and a final material test matrix to generate a material datasheet for the chosen resin modified with nano-SiO2 and also the recyclable composites laminates produced by CETMA.

The use of nano-SiO2

Regarding the use of nano-SiO2 particles, TWI characterized and functionalized pyrogenic silica and Stöber silica powders. Next, TWI carried out a study on the viscosity versus loading behaviour of different silica powders in model resin in order to establish a pathway for silica incorporation procedure.

Upon the results of rheology study, ten modified samples were prepared for EIRE, five modified powder epoxy and five modified liquid epoxy resin samples with different loading ratios. For each of those samples, 1,3-dioxolane, a solvent selected based on Hansen Solubility Parameter (energetic) considerations, was used to reduce the inherent viscosity and facilitate mixing.

EIRE Manufactured preliminary test panels using the five initial powder epoxy-SiO2 and five initial epoxy-SiO2 infusion resin samples, prepared by TWI, reinforced with UD glass fibre. On the one hand, all 5 powder epoxy – SiO2 sample panels contained an unsatisfactory surface finish. It appears that the nano-SiO2 particles are incompatible with the powder epoxy process resulting in panels that contained substantial visual defects such as, dry fibres and lumps of dry nano-SiO2 particles scattered across the panels. This was most likely the effect of uncontrolled silica particles dispersion. Those panels were deemed unfit for testing and thus, powder epoxy-SiO2 developments were not selected as preferred strategy.

Images of control and reinforced panel developed with SiO2
Figure 1. Defect-free powder epoxy control laminate (left) and powder epoxy SiO2 sample laminate with defects (right).

On the other hand, such dispersion problems were not associated with epoxy resin modification with 3 of the 5 epoxy-SiO2 infusion resin samples successfully infused, while the other 2 samples had a viscosity that was too high for the infusion process. EIRE carried out the preliminary material test matrix and the best performing epoxy-SiO2 infusion resin sample was chosen for the final material test matrix.

dispersion problems were not associated with epoxy resin modification
Figure 2. GF/epoxy-SiO2 laminate with preliminary test specimen extraction locations.

The use of Vitrimers/TPR recyclable resins

One of the project objectives states that MAREWIND will provide the design of new composites with intrinsic ability to be reprocessed and recycled, and that can also be easily processed using the same technologies used for thermosetting resin. The goal is to get a recyclable content in the composite above 40% of total. In respect to new recyclable resins, CETMA has carried out a commercial scouting to select the most suitable resin system for the wind industry in terms of physical and mechanical properties (durability and service temperature among others). Also, the composite matrix should be able to contemporary ensure recyclability requirements and suitable parameters for the intended infusion process.

Polymeric material developers’ attention is more and more focused on new types of recyclable polymer material: thermoplastics reactive resins (TPR) and vitrimers.

Based on results of preliminary material selection, it was found that industrial production of vitrimers is still under development, and among the scarce materials available to date, no commercial products were found with suitable properties for the infusion process defined, mainly regarding viscosity.

A new TPR (thermoplastic reactive resin) system Elium 188 XO, developend by Arkema has been successfully tested.

Apart from the main strategies studied, recyclable thermosets (RT) – epoxies in particular – were then investigated as an additional alternative related to recycling. The use of the cleavable amine hardener Recyclamine R101 (formerly developed and patented by Connora Technologies, USA and acquired in 2019 by Aditya Birla Chemicals, India) allows the recyclability of the matrix recovering both the clean fibers and a de-crosslinked epoxy (i.e. thermoplastic).  Different epoxy resins have been preliminarily evaluated, then focusing the work on the standard system Gurit Prime 27 provided by EIRE with Recyclamine R101 hardener.

Thermal and rheological characterization of the above resins (TPR Elium 188XO and cleavable epoxy resin) were performed to analyse the reactivity of the systems, to set up the infusion parameters and also provide preliminary input data for the numerical model of such process.


The use of RCF

CETMA has set up the infusion process and manufactured composite laminates based on RCF and UD GF as reinforcements and TPR Elium and Recyclable Epoxy resin. Process optimization was performed in order to maximize the mechanical and physical properties and comparing them with traditional composite laminates based on GF and epoxy resin.
Images related to the manufacturing infusion process of composite laminates
Figure 3. Images related to the manufacturing infusion process of composite laminates.

CETMA has defined the numerical model for the simulation of the resin infusion process in terms of the set-up, numerical parameters and the boundary conditions. The physical process is modelled by the Navier Stokes equations which in this case describes the mass, momentum and energy conservation of the resin flowing into a porous medium. To solve these equations the numerical method called FVM (Finite Volume Method) is used so far for the process optimization and will be used to optimize the infusion process on the full-scale demonstrator.

To solve these equations the numerical method called FVM (Finite Volume Method) is used. The model has shown great accuracy in simulating the resin flow in the infusion tests performed on small coupons and will be used to. to optimize the infusion process on the full-scale demonstrator. With regards to the thermo-mechanical recycling of TPR Elium 188XO with glass fiber laminates some preliminary tests have been done in order to evaluate the technical feasibility of these materials to be recycled and to be compression moulded, manufacturing two recycled flat panels.

CETMA has also developed a multi-scale numerical model to predict the macromechanical properties of the recycled materials based on RCF and Epoxy resin. Starting from the material properties of the composite constituents (fibres and matrix) and the microstructure characteristics (fibres volume fraction, fibres shape and orientation), a Representative Volume Element (RVE) of the composite material has been generated. A virtual characterization of RVE has been carried out to investigate the stiffness considering different loading conditions and the numerical results have been compared with the experimental ones. From the comparison was observed that the numerical results are in good agreement with the tensile modulus derived by experimental tests.

Numerical analysis results
Numerical analysis results

Full-field measuring techniques of wind blade working conditions

INEGI is developing a non-destructive testing system (NDT) which is intended as a first version of the final blade testing system to be developed in the coming months. The main results achieved include the definition and execution of NDT laboratory setups using DIC and IR solutions, the selection of the necessary equipment, as well as the development and successful use of the proposed trigger solutions.

Concerning the digital image correlation analyzes, two first approaches have already been carried out, namely the establishment of a system for evaluating displacements using static cameras with static blades, and them using static cameras with a rotating blade. For the defect detention system using thermography, several approaches were evaluated, and the most successful was found to be the use of an algorithm that does image comparison between thermographic images, one with a defect-free blade, used as a reference and one as the test subject.

DIC laboratorial setup and IR testing setup for testing wind blades working conditions
Figure 1. DIC laboratorial setup (left),  IR testing setup (right)

INEGI will continue with the presented plan and carry on with the remaining activities, especially with regard to the development using the structure from motion approach to carry out DIC analyzes with floating cameras, as well as with the establishment of the limits and strengths of the different thermographic approaches.


Implementation and assessment of FBGs/DFOs technologies

INEGI found that the materialization of several SHM laboratorial setups using both FBG and DFO technologies was successful, and validated the assumptions and decisions that were made, thus being ready to be implemented in the real-life scenario SHM.

Likewise, CETMA has shown the feasibility of FO distributed sensors to be applied as monitoring system in reinforced concrete structures. In particular, the developed SMART rebars (i.e., rebars with embedded FO sensors) show the following essentials points:

      • An SHM system based on SMART rebars with distributed FO sensors can provide thousands of sensing points that permits mapping of strain distributions the reinforcement of the structure.

      • The FO sensors provide the same results of traditional strain sensors in terms of reliability, with many advantages among which multiparameter measurements with the same sensor, no need of recalibration, easier wiring, high resistance in hard environment.

      • The developed embedding near surface technique of the FO sensors in the rebars is easy to realize and reliable; validation results on tensile strength test showed good behaviour.

      • The developed decoupling system permits to create segments of FO sensors not subjected to mechanical stresses.

      • The lab-trials related to the embedding process of SMART rebars demonstrated that the developed technique for the protection of the sensor in the inlet/outlet points of the FO cables both from the rebar and the concrete works properly; a 100% rate survival was achieved for all the typologies of concretes.

      • The lab trials related to mechanical tests on concrete elements with SMART rebars inside demonstrated the capability of the developed SHM system to properly detect different typologies of mechanical stresses (i.e., flexural, compression).

The activities developed will be used and furtherly implemented for SHM system for blade monitoring and concrete structures monitoring.


Modelling of GBS structure and influence of tested materials

INEGI finds as main results the definition of the design of the GBS and the study of the environmental conditions of the test site, as well as the numerical study of the structural forces on the GBS coming from the sea states and the transport and handling processes.

They also identified as the main next step to carry the planning and definition of the open sea test to be executed within the context of this project. Additionally, INEGI will continue to perform FEM simulation to study the structural integrity of the structure.


Development and validation of FEA model of composite structure for blades

The results from the MAREWIND Excel tool for the calculation of the transverse elastic and shear modulus show a better agreement with the available data using the Halpin-Tsai equations instead of the constant stress model. The MAREWIND tool has been validated for both the micro-mechanical and macro-mechanical part. Concerning the micro mechanical validation, good agreement with the reference results has been obtained. The Halpin-Tsai results are in excellent agreement with a negligible deviation.

The stress and strain calculated show excellent agreement with the reference results. Failure Analysis was performed with a unidirectional load in order to validate Tsai-Hill Failure Theory of Excel Tool and also in this case, the obtained results show an excellent agreement with the reference ones.

Likewise, the FE model tool has been validated for both the micro-mechanical and macro-mechanical part. For the macro-mechanical model, the deviations are smaller than 1% and therefore the experimental results of the literature and the numerical ones are in excellent agreement. Thus, both the micro- and macro-mechanical FE models can be considered validated.

The objective will be to use the high-resolution FE model of composite and tool to compare their results against the experimental data that will be made available by partners performing tests on the materials selected for the next phases of the project. The obtained results will be the basis for conducting the activities foreseen referred to the simulation of the blade prototype (or part of it) predict the fatigue life of the wind turbines.

A fouling-preventing coating for different materials of offshore submerged structures has been developed and characterised at laboratory scale. In the first steps, two different base coatings were developed: low curing temperature and higher curing temperature.

The complete system, in both cases, implied a two-layer treatment, with a second thin layer focused in reducing the contact of the biological matter to the surface of the different materials. In the last months, based on a room temperature curing strategy, TECNAN and Lurederra developed a one layer system with oleo and hydrophobic final properties as the two other systems. All of these base matrixes and the one-layer system matrix, have similar colour, density, viscosity and stability overtime.

In addition, samples of materials with different chemical nature were selected in order to apply and validate the coating formulations. In particular, these materials are metal, painted metal and various polymers.


Applications of the antifouling coatings

The application selected was the spray gun because of its versatility for the target substrates. TECNAN has been working in the adjustment of the parameters such as the atomisation pressure, liquid flow and the fan width among others.

In the particular case of the hydrophobic properties, considering that the contact angle 90º is a good result reference, the values obtained of the different substrates tested in all the treatments developed, are quite inspiring.

Hydrophobic properties on stainless steel and painted metal
Figure 1. Hydrophobic properties on stainless steel (Matrix C) and painted metal (Matrix A + top coat)

In the case of the repellence of oil, very good results have been obtained too, not only in metal but also in polymeric substrates which have low reactivity and some initial repellence that imply a bigger challenge to generate a suitable and functional coating layer on it.

Cross-cut test on EDF coupons, oleophobic effect in polyamide and POM and roughness measurement on polyethylene
Figure 2. Cross-cut test on EDF coupons, oleophobic effect in polyamide and POM and roughness measurement on polyethylene

As a consequence, we could highlight the good results with the latest developed formulation based on one layer and low curing temperature, in relation with the adherence and compatibility with the substrates and the final repellence properties. The future work on the technologies validation and manufacturing, will be following this formulation strategy.


Tests in real environments

Enerocean in close cooperation with Lurederra and Tecnan, also defined and prepared the samples for the regulations ASTM D3623 and ASTM D5479, with the selected formulation ©. The materials selected for these tests were Nylon as the polymeric substrate and stainless steel as the metallic substrate. Enerocean was in charge of getting the samples and Lurederra of coating them with the protocols from Tecnan.

EDF polymeric coupons coated and the two substrates (metal and polymer) sent to Enerocean once coated
Figure 3. EDF polymeric coupons coated and the two substrates (metal and polymer) sent to Enerocean once coated

Evaluation of the coatings

EDF has carried out studies on the evaluation of the coatings. Currently, antifouling coatings are subjected to a series of conditions in order to be suitable for real applications and also, the performance must be determined by three properties:

  • Ability to limit biofouling
  • Low fouling adhesion and resistance of the coating to mechanical
  • Chemical damages

Products belonging to the range of Chugoku Marine Paints have been selected in order to carry out comparative testing with the new solutions in development. These products consist of two different layers: ECOMAX Bi (base coat) and BIOCLEAN ECO (top coat), and it is based on non-biocidal technology. Lurederra and Tecnan have applied it and tested it on some substrates showing that the final thickness of the mentioned commercial product layers is quite significant meaning that the weight of the structures can increase in a considerable way, its appearance can change and the application can be extremely difficult.

Polycarbonate piece coated with commercial product and the hydrophobic properties
Figure 4. Polycarbonate piece coated with commercial product and the hydrophobic properties

Based on the commercially available systems, the selection of the wind turbine blade coating for trials was undertaken. In order to achieve the desired repellence (superhydrophobicity) and erosion resistance, TWI has incorporated functional additives into the selected coating matrix. All selected additives were based on materials which have previously been demonstrated to be platforms for superhydrophobic surfaces.

These additives are inorganic metal oxides that are capable of surface functionalisation to enable their native hydrophilic surfaces to be transformed into exhibiting hydrophobic behaviour. The key additives explored are:

  • Stöber derived TWI silica

  • Metal oxides (TECNAN’s silica manufactured using pyrogenic methods and commercially available pyrogenic silica Aerosil 200)

TECNAN's SiO2 functionalized with HMDZ (left) and f-HMDZ (right) deposited onto glass slides
Figure 1. TECNAN’s SiO2 functionalized with HMDZ (left) and f-HMDZ (right) deposited onto glass slides.


Comparison of contact angle between silica powder without (left) and with (right) HDMZ treated silica product added
Figure 2. The particle functional performance change associated with surface functionalization. Trimethylsilylation is capable of changing pyrogenic silica behaviour from hydrophilic to superhydrophobic.

The mentioned functionalized silicas were incorporated into PU model matrix system in a various combinations and various loading levels. TWI have undertaken wettability, abrasion, adhesion and chemical resistance tests, whereas EIRE took care of rain erosion examination. INL have been given coated samples to perform long-term weatherability study.

All developed coatings improved the repellent characteristics of commercial model matrix system. Satisfactory results were also obtained from adhesion, abrasion and chemical durability tests. Nevertheless, the erosion resistance of those coatings was still not reaching target values and therefore, second generation coatings were developed.


Next steps

Further minor coating modifications will be done – addition of second functionalization might be necessary in order to bind silica particles with model matrix system via covalent bonding and thus, to increase the resistance towards rain erosion. The result from the rain erosion study suggested that developed coatings were too hard and this is not beneficial in terms of providing the resistance towards flowing water. Therefore, silica microparticles won’t be functionalized at all, to prevent and increased hardness caused from bonding together or to the matrix.


During the first 18 months of the project, the MAREWIND Consortium has been working on the development of an anticorrosion coating for key metallic elements. The coating consists of three layers with different chemical compositions and, therefore, different corrosion protections. Moreover, the multilayer system has been developed layer by layer:

  • Layer 1 has a metallic composition providing the substrate with a good cathodic protection. Considering the low curing temperature and stability overtime, two main matrix formulations were investigated, as well as various metallic components and loads.

  • Layer 2 incorporates a self-healing system based on core-shell micro/nanofibers. Nanofibers were produced and optimized regarding viscosity of each material and prepared by electrospinning technique. Then, they were completely characterised in terms of textural, morphological and chemical properties, revealing an increase in corrosion protection close to 40 times.

  • Layer 3 was designed as an Organic Inorganic Hybrid (OIH) sol-gel matrix with reinforcements of fibres and ceramic nanoparticles. The formulation has been adapted and optimised to provide the coating with additional properties such as increased mechanical strength and hydrophobicity to protect even more the target metallic offshore structures.

Multilayer system with different chemical composition and corrosion protections
Figure 1. Multilayer system with different chemical composition and corrosion protections

Different systems were proposed regarding matrices and curing procedures at low, medium and high temperature. Also, an exhaustive work regarding coating application methods as well as the characterisation of coated samples has been performed. With these results, finally the system of anticorrosion coating has been achieved in low temperature strategy.

Coating application systems

Two strategies were designed for this purpose:

  • Application via spray gun:

    A suitable procedure depends on the adjustment of the spray gun parameters to obtain uniform and smooth coatings. TECNAN was able to generate a reference protocol for each layer defining main parameters involved in the application process such as atomization pulverization, flow rate.

  • Application via dip coating:

    Dip coating is more appropriate for applying the coatings on a large number of small metallic elements. A small-scale device has been designed for a preliminary adjustment of the coating application.


The results show that spraying is the main alternative, since it provides a good surface finish, being applicable for different morphologies and sizes, while immersion is more focused on small elements with very complex geometries. Also a successful application of whole protections systems has been carried out, revealing good interactions between layers.

Characterisation of the coatings

This step was performed in Lurederra’s laboratory and saline mist chamber, INL facilities and TSF specific assessment. In this context, it took place the characterisation of the treated samples in terms of performances for each corrosion protection system, regarding adherence, corrosion resistance, hardness, among others. Complementary information has been generated related to microstructure, textures, defects and surface details.

The investigations showed promising results regarding corrosion protection, reaching to more than 4.200 hour of protection in saline mist chamber and successfully comply with corrosion aging test including exposure to salt spray in combination with UV, water condensation and freezing conditions according to ISO 12944-9.

Real samples inside the saline chamber showing no corrosion, and UV resistance tests carried out on flat samples for aging validation
Figure 2. Real samples inside the saline chamber showing no corrosion, and UV resistance tests carried out on flat samples for aging validation


MAREWIND project will develop durable materials and recyclable solutions for the offshore wind industry, while extending the service life of the wind facilities and creating new job opportunities.

Nowadays, the wind turbine blade leading-edge erosion affects the annual energy production by 4-20 %. That equates to a loss between €152-760 million a year across the overall European offshore wind sector. Moreover, the maintenance of the materials is very expensive and accounts for around 25% of the offshore wind farms’ cost. In addition to that, at the end of the wind turbines’ service life, the generated waste in need of recycling can increase up to 800,000 tones per year in Europe by 2050.

MAREWIND solutions will pave the way for the next generation offshore wind generators and facilities that aim to solve the technological, economical, business, and societal challenges we are now facing. In addition, it will strengthen the leading role of Europe in the global offshore wind market with current 22,072 MW of installed cumulative capacity, followed by Asian and North America markets.

Meet the consortium

Progress achieved after 18th months

It has been a busy and productive first phase of the project MAREWIND project. Since its launch in December 2020, the MAREWIND team has been working hard on progressing to achieve the ambitious goals of the project. The project addresses the main aspects related to materials durability and maintenance in offshore structures which have the potential to reduce imply failure, misfunctioning, loss of efficiency in energy generation and which have a major repercussion on O&M and CAPEX. MAREWIND aims to develop durable materials and recyclable solutions for the offshore wind industry, while extending the service life of the wind facilities. In addition, the project outcomes will also contribute to meeting the EU climate targets and create new job opportunities within the wind industry.  

MAREWIND project has achieved its second milestone!

Second milestone of the project has been successfully achieved! During the first year and a half, most of the technical work done by the partners has focused on the fabrication and testing elements individually. Specific formulations have been selected after testing and checking accelerated essays which comply with technical requirements. A great progress has been done thanks to the close collaboration between the partners of MAREWIND consortium. We are looking forward to sharing the outcomes we will achieve in the upcoming years!

Next steps

The consortium is preparing its third newsletter, so stay tuned for more details about the progress achieved so far. You can subscribe for the latest MAREWIND news and events, here.