The ongoing depletion of global fossil fuel resources and greenhouse effect of harmful emissions have made the development of renewable energy a universal priority. Tidal energy is one of the renewable energy sources that offers a viable alternative. However, one of the primary challenges in tidal turbine applications is the erosion of turbine blades caused by challenging marine environmental conditions. This study investigates the erosion behaviour of glass fibre-reinforced polymer (GFRP) in sea water conditions over an extended pre-exposure period of 183 days (4380 h). To achieve this, a custom-designed slurry erosion impingement rig was developed and is detailed in this paper. The results reveal significant changes in the erosion mechanisms of GFRP as a function of prolonged pre-exposure, with critical implications for the suitability of the material in tidal turbine blades for tidal energy applications. Advanced characterisation techniques, including erosion wastage maps, micro-profiling, and SEM, were employed to analyse surface degradation and erosion patterns. These tools provide insight into material performance and support the optimisation of GFRP for reliable, long-term operation in tidal energy environments.

Tidal energy offers significant potential for renewable power generation, but blade erosion threatens turbine reliability over their targeted 25-year service life. This study examines erosion mechanisms in tidal turbine blades, focusing on testing FR4 glass fibre-reinforced polymer (GFRP) composites under accelerated erosion conditions with sand particles (100-150 mu m) at 12.5 m/s flow velocity and varying impact angles (30 degrees, 45 degrees, 60 degrees, 90 degrees). Experimental results reveal maximum erosion occurs at 60 degrees impingement angles, with mass losses reaching 0.7 % after a 90-minute exposure, indicating a mixed ductile-brittle erosion response. Surface roughness measurements demonstrate a characteristic W-shaped erosion profile at 90 degrees impingement, with maximum depth variations of 140 mu m at 60 degrees impact angles. The study establishes correlations between mass loss and surface roughness parameters, showing that arithmetic mean roughness (Ra) is the least sensitive to erosion, while total roughness height (Rt) exhibits the strongest correlation. The selected roughness parameter (Rz) shows moderate sensitivity, increasing from 40 mu m to 150 mu m as mass loss progresses from 0.1 % to 0.8 %. Tests conducted with different sand sizes (0-50 mu m, 50-100 mu m, 100-150 mu m) in saltwater (3.5 % salinity) reveal particle size dependence of erosion rates. Surface analysis using 3D optical scanning (10 nm vertical resolution) quantifies progressive damage from microscopic pitting to material removal exceeding 200 mu m depth. Computational fluid dynamics simulations at 90 degrees impingement demonstrate stagnation point effects, explaining the characteristic erosion patterns observed. The research highlights that blade hydrodynamic performance may degrade significantly before structural failure, with surface roughening affecting efficiency even at early erosion stages. The review concludes by identifying critical research needs, including the development of erosion-resistant composites, real-time monitoring techniques, and validated numerical models for predicting erosion progression. This comprehensive understanding of erosion mechanisms and their quantified effects is essential for improving tidal turbine reliability and commercial viability.

The tribological mechanisms of potential composite materials that could be used in tidal turbines considered the effects of various erosion parameters on the degradation modes, both with and without particles, in still and seawater conditions. The aim of this study was to investigate the potential of a specialised epoxy erosion-resistant coating for glass fibre-reinforced plastic (GFRP) in resisting the impact of slurry erosion. Slurry erosion is a process by which solid particles suspended in a fluid medium impinge on a surface, causing material loss due to repeated impacts. The coating efficacy was evaluated through a series of tests, including three different speeds and six different impinging angles and the results were used to generate tidal turbine maps. The study provided insights into the durability and of the epoxy and potential use of the coating in tidal turbine blade industries where resistance to erosion is crucial for long-term performance and safety.

Raindrop erosion of wind turbine blades’ leading edge is a critical degradation mechanism limiting wind turbine blade lifetime and aerodynamic efficiency. Protective coatings have been extensively studied to mitigate this damage. This review critically synthesises current knowledge on coating-based protection strategies against erosion, with emphasis on (i) the underlying mechanisms of erosion, (ii) advances in conventional and emerging coating technologies, and (iii) experimental approaches for testing and lifetime prediction. Across reported studies, nanofiller reinforcement (e.g., CNTs, graphene, CeO2, Al2O3) enhances erosion resistance by 60–99%, primarily through improved toughness and stress-wave dissipation. Hybrid and multifunctional systems further combine mechanical durability with self-healing or anti-icing capabilities. Experimental results confirm that erosion rate follows a power-law dependence on impact velocity, with maximum damage occurring between 45° and 60° impact angles. Softer elastomeric coatings demonstrate longer incubation periods and superior viscoelastic recovery compared with rigid sol–gel systems. Persistent gaps include the lack of standardised testing, poor field–lab correlation, and limited long-term durability data. Future work should focus on coordinating multi-stressor testing with variable-frequency rain setups to replicate real field conditions and enable reliable lifetime prediction of next-generation erosion-resistant coatings.

Rain erosion testing of wind turbine blade coatings is still based almost entirely on kinetic test parameters while ignoring the temperature–salinity domains that control field damage. This short communication quantifies how far current rain erosion test conditions diverge from offshore environmental temperature–salinity envelopes. Using seas surface climatology for four offshore regions (North Sea, US Atlantic shelf, Taiwan Strait–South China Sea, Bass Strait) and temperature and water composition parameters from 11 water-based erosion studies, we show the environmental sea surface temperature (SST) spans 5 – 17 °C in the North Sea and 8 – 24 °C in the US Atlantic, rising to 20 – 32 °C in the Asia–Pacific and Bass Strait, with sea surface salinity (SSS) typically 31 – 35.5 PSU. In contrast, all reported droplet erosion tests were run between 18 and 29 °C; three of 11 used only freshwater (~ 0 PSU) and the remainder a single seawater-like level (3.0 – 3.5% NaCl, ≈30 – 35 PSU). No study combined marine salinity with cold (<10 °C) or tropical (≥28 – 30 °C) temperatures, despite evidence of markedly higher damage in saline media and up to an order of magnitude increase in polyurethane rates near the glass transition region.

Over the lifetime of a wind turbine, the blades receive significant erosion to the leading edge caused by precipitation, leading to large losses in aerodynamic performance and therefore power output. It is therefore prudent to study the mechanics of the erosion process in order to predict and mitigate these losses. Whilst leading edge erosion due to raindrop impact has received much research attention in recent years, very little research has focussed the role of hailstone impact in erosion in wind turbine blades. This paper aims to use a computational simulation model to investigate and characterise the physics of the impact of a hailstone on a flat plate of composite glass fibre material typical of those used in the construction of wind turbine blades. This was achieved by modelling the ice projectile using a Single-Particle Hydrodynamic approach in the software package LS-DYNA. This simulation was used to determine how the impact response in the target plate was affected by various parameters of the impact scenario. Simulations were run using diameters of hailstone between 5 and 20 mm, impact speeds between 80 and 120 ms−1, and at angles of incidence between 90 and 0 degrees. The paper presents these observations in the form of “maps” of the material response at each angle of incidence. It was observed that whilst at low velocities, the material response varies linearly with diameter and velocity and at higher velocities, more complicated behaviour arises due to the interaction between the initial stress wave and the remainder of the impacting projectile.

This paper investigates the effects that rain drop erosion has on the integrity of wind turbine materials. This research involves analysis of impact models and theoretical equations to simulate the impact phenomena when a raindrop collides with a wind turbine blade at high speed. Impact phenomena that occur when a raindrop impacts with a wind turbine blade were evaluated. Additionally, the use of various types of software was considered to simulate this impact event. The model results of the raindrop impact with respect to a comparison of the governing equations and impact behaviour are addressed. Future work is outlined including adding variables to the erosion modelling algorithms.

Wear by hard particles can involve abrasion or erosion and is one of the most severe forms of wear. When a corrosive environment is present, the material loss rate can be significantly increased due to interactions (synergy) between the mechanical and chemical/electrochemical actions. In developing strategies for mitigating such adverse synergistic effect, it is important to understand the complex effect of various parameters on material loss under given tribocorrosion conditions. In this paper, a model is presented for wear-corrosion synergy in abrasive wear by hard particles applicable to many conditions in both the marine renewable (abrasion by high concentrations of large sand particles on tidal turbines) and extractive metallurgy (abrasive wear in mineral extraction). The mechanical wear loss is modeled based on the grooving mechanism (micro-cutting/micro-ploughing). Wear-enhanced corrosion is calculated from the fresh surface areas generated by grooving and the corresponding transient corrosion current. The concept of “corrosion-degraded layer” on the worn surface is introduced to account for the corrosion-enhanced wear; within this corrosion-degraded layer, the material loss rate is higher under the same mechanical wear conditions than in the material that is unaffected by corrosion. Based on the model, the effect of wear conditions on synergy in hard particle wear-corrosion has been discussed. The relative thickness of the corrosion-degraded layer to the depth of hard particle penetration (grooving) in the mechanical wear is found to be an important parameter in determining the relative severity of synergy in different tribo-corrosion systems. Good qualitative agreement has been observed between the predictions and published experimental results obtained from a range of abrasion-corrosion and erosion-corrosion lab testing.

AbstractTribocorrosion in passive metals involves a complex and interactive mechanism between mechanical and electrochemical actions at a rubbing contact in a corrosive environment. The mechanical wear mechanism disrupts the passive film on the metal surface; and instantly, the metal repassivates and dissolves in the corrosive environment. This surface damage failure can occur in various components such as marine structures and medical implants which can force significant downtime and repair costs. In this article, historical advancement in the well‐known theories and models which have been developed for passivation and tribocorrosion current (as a measure for wear‐accelerated corrosion) is presented and discussed. The strengths and limitations associated with the models are reviewed to generate an overall picture of the progress in the field. The links between different models are also discussed and finally, some possible directions for future research are suggested.

Tidal energy, with its potential to provide a consistent energy output and reduce carbon emissions, has garnered significant interest. This study, which evaluates the performance of tidal turbine blades in seawater conditions and with sand particles, presents a novel approach. A slurry rig was developed to examine composite materials, and a glass fibre-reinforcement polymeric material was tested over a range of particle sizes, velocities, and impact angles. In addition, this paper used a new test protocol with 14 days (336 h) and 91 days (2184 h) of pre-exposure time of materials before testing. The results, which show significant changes in the erosive mechanisms of GFRP in short- and long-term pre-exposure time as a function of these variables, have profound implications for the design and performance of tidal turbine blades. The study also utilised scanning electron microscopy (SEM), depth profiling analysis, and erosion mapping techniques to compare the erosion behaviours of GFRP. These tools can be used to optimise such materials in tidal turbine conditions.

Leading edge erosion is becoming increasingly important as wind turbine size and rainfall are predicted to increase. Understanding environmental conditions is key for laboratory testing, maintenance schedules and lifetime estimations to be improved, which in turn could reduce costs. This paper uses weather data in conjunction with a rain texture model and wind turbine RPM curve to predict and characterise rain erosion conditions across Ireland during rainfall events in terms of droplet size, temperature, humidity and chemical composition, as well as the relative erosivity, in terms of number of annual impacts and kinetic energy, as well as seasonal variations in these properties. Using a linear regression, the total annual kinetic energy, mean temperature and the mean humidity during impact are mapped geospatially. The results indicate that the west coast of Ireland and elevated regions are more erosive with higher kinetic energy. During rain events, northern regions tend to have lower temperatures and lower humidities and mountainous regions have lower temperatures and higher humidities. Irish rain has high levels of sea salt, and in recent years, only a slightly acidic pH. Most erosion likely occurs during winters with frequent rain infused with salt due to increased winds. After this analysis, it is concluded that Ireland’s largest wind park (Galway) is placed in a moderate-highly erosive environment and that RET protocols should be revisited.

Erosion-corrosion maps rarely take into consideration the role the rebound velocity has in extending the transition boundaries. Furthermore, although impact angle is an important and widely studied variable in experimental erosion-corrosion mapping, there have been few studies on theoretical treatments of this variable on such maps. In addition, the role of pH in changing the transition boundaries has been rarely modeled. In this chapter, the effect of elastic rebound velocity and impact angle on erosion-corrosion maps are explored at various pH values. How such variables can be modeled are indicated and future directions in this field are suggested.

In renewable energy, wind capture has been expanding to now have one of the largest presences in the global green energy sector. With the drive to expand low carbon technologies; maintenance of the engineering components of wind turbines is crucial and in particular the monitoring of the leading edge of turbine blades which experience high impact velocities in service. Surface changes due to rain drop erosion can reduce energy conversion due to a loss of aerodynamic efficiency. This is one of the key areas of interest, as even small aerodynamic changes can lead to 2–3% loss in annual energy. Inspection methodologies of turbine blades are basic, involving an observation and high-definition photographs of the damage. Recent studies on the rain erosion of turbine blade materials show that this standard procedure often fails to characterise the loss of aerodynamic efficiency in these turbine blades in. With the industry moving in the direction of leading-edge profile samples, there is a consensus that whirling arm type test rigs are the most applicable testing regimes. Presently there is little overlap in the analysis used in different studies. This review considers various techniques which may be used to inspect and characterise the materials performance following exposure to rain drop erosion. These techniques will be evaluated based on their potential use within the industry. Findings conclude that a combination of techniques is optimal to analyse surface defects and that subsurface analysis is an important factor that must be considered in any investigation of long-term blade integrity.

Hail impact-induced erosion has the potential to significantly affect the operational lifetime of structures exposed to extreme weathering environments such as hail events. Computational materials modelling can be used to better understand the erosion behaviour during a hailstone impact, and here the relevant background work is detailed. In this paper, an implementation of an ice impact model, utilising Smooth Particle Hydrodynamics along with a highly strain-rate-dependent material model, is shown, and its results and limitations discussed. An overview is given on the literature on modelling hail events, including the history of experimental work. The various potential modelling methods which have been developed is then given, along with an evaluation of the suitability of the methods to future work in this area.

Within renewable energy, challenging climates can impose great limitations on power generation. In wind energy, rain erosion on turbine blades can create major disruptions to air flow over the aerofoil, reducing the efficiency of the blade and immediately affecting the power output of the turbine. The defects in the materials that cause these inefficiencies are known and can be observed on turbines that have been in operation for extended periods. This work explores the transitions between different wear states for G10 Epoxy Glass under laboratory simulated wind turbine conditions in operation and measures the wear periodically to identify a progression of erosion. Mass loss data and micrographic analysis revealed samples at 45° and 60° displayed increasing erosion when examining erosion performance for angles between 15° and 90° over various exposure and velocities. Erosion maps were constructed, showing the variation of wastage and identifying the performance window of conditions where degradation is minimised.

A correction to this paper has been published: https://doi.org/10.1007/s40735-021-00534-3

Erosion of tidal turbine blades in the marine environment is a major material challenge due to the high thrust and torsional loading at the rotating surfaces, which limits the ability to harness energy from tidal sources. Polymer–matrix composites can exhibit leading-blade edge erosion due to marine flows containing salt and solid particles of sand. Anti-erosion coatings can be used for more ductility at the blade surface, but the discontinuity between the coating and the stiffer composite can be a site of failure. Therefore, it is desirable to have a polymer matrix with a gradient of toughness, with a tougher, more ductile polymer matrix at the blade surface, transitioning gradually to the high stiffness matrix needed to provide high composite mechanical properties. In this study, multiple powder epoxy systems were investigated, and two were selected to manufacture unidirectional glass-fiber-reinforced polymer (UD-GFRP) plates with different epoxy ratios at the surface and interior plies, leading to a toughening gradient within the plate. The gradient plates were then mechanically compared to their standard counterparts. Solid particle erosion testing was carried out at various test conditions and parameters on UD-GFRP specimens in a slurry environment. The experiments performed were based on a model of the UK marine environment for a typical tidal energy farm with respect to the concentration of saltwater and the size of solid particle erodent. The morphologies of the surfaces were examined by SEM. Erosion maps were generated based on the result showing significant differences for materials of different stiffness in such conditions.

Chromium (Cr) containing steels were tested to analyse corrosion behaviour in carbon dioxide saturated water of varying salinities with extended exposure time. Both potentiodynamic and mass loss data were collected to gain a better understanding of the corrosion mechanisms. It was found that both the high Cr steels displayed degradation in the form of pitting with increasing salinities. However, the low alloy steel reference material showed uniform iron carbonate (FeCO 3 ) precipitation. The use of high salinity precipitated layers to aid corrosion protection in lower salinity seawater environments was then established as an interesting area for greater examination. Subsequently, samples of the low alloy steel previously corroded in solutions of 7, 14 and 28% sodium chloride (NaCl) concentration were then tested in seawater salinities of 3.5% NaCl. It was found that both the 7 and 14% NaCl pre-corroded samples resulted in a significant reduction in the corrosion rate when compared with non-pre-corroded samples. The 7% NaCl pre-corroded sample showed the greatest reduction in corrosion rate, and through SEM analysis of the layer both on the surface and cross-section it was found to display an iron carbonate layer more densely packed and defect free. This indicated the potential benefits of high salinity pre-corrosion techniques to aid protection in seawater environments.

The effect of chloride on erosion-enhanced corrosion was studied experimentally and by a multiphysics algorithm developed to describe the erosion-corrosion interactions. API 5 L X65 steel was exposed to a slurry jet of different chloride content (0.005, 0.05 or 0.5 M) containing silica particles (250-350 mu m). An electrochemical-transport-reaction model was used for numerical simulation of polarization curves. Visualization of the flow conditions was also carried out in this work. The effect of erosion on corrosion was found to be well described as a proportionality factor between the kinetics constants of the electrochemical reactions with and without the erodent. The presence of chloride was found to affect the system mainly through increased conductivity of the electrolyte.

Raindrop erosion is a significant materials limiting issue. It can affect materials for transportation and renewable energy converters such as wind turbines as well as all external structures used in the construction industries. In such cases, the raindrop effects can occur over a wide range of impact velocities and particles sizes. In understanding tribological variable effects, it is useful to study using reference materials. This is because the reference material is well characterized, from previous knowledge of the tribological and corrosion patterns. Further, the well established chemical composition and stochiometry of the corrosion products provide some background understanding of how effectively, during tribological action, the surface scale adheres to the substrate. In this study, a carbon steel was used as a reference to study the effects of velocity and drop diameter in a whirling arm erosion test rig. The results were used to establish the conditions where corrosion was accelerated and the environments where aerodynamic effects may have resulted in droplets being deflected the surfaces. Erosion maps were generated to illustrate such mechanisms based on the results.