Search Results (28)

To improve environmental sustainability and operational safety in maritime industries, the development of efficient methods for removing biofouling from submerged surfaces is critical. This study investigates the erosion mechanisms of cavitation jets as a non-contact, high-efficiency method for detaching marine organisms, including bacteria and larvae, from ship hulls and underwater infrastructure. Through erosion experiments on coated specimens, variations in jet morphology, and flow visualization using the Schlieren method, we examined how factors such as jet incident angle and nozzle configuration influence removal performance. The results reveal that erosion occurs not only at the direct jet impact zone but also in regions where cavitation bubbles exhibit intense motion, driven by pressure fluctuations and shock waves. Notably, single-hole jets with longer potential cores produced more concentrated erosion, while multi-jet interference enhanced bubble activity. These findings underscore the importance of understanding bubble distribution dynamics in the flow field and provide insight into optimizing cavitation jet configurations to expand the effective cleaning area while minimizing material damage. This study contributes to advancing biofouling removal technologies that promote safer and more sustainable maritime operations. Full article

Antifouling coatings are integral to the maritime economy. The efficacy of the applied painting system is closely correlated with susceptibility to fouling and the adhesion strength of contaminants. A fouled hull might result in an elevated fuel consumption and journey expenses. Biofouling on ship hulls also has detrimental environmental consequences due to the release of biocides during maritime travel. Therefore, it is imperative to develop eco-friendly antifouling paints that inhibit the robust adhesion of marine organisms. This study aimed to assess a biocide-free antifouling coating formulated with polymers intended to diminish molecular adhesion interactions between marine species’ adhesives and the coating. The evaluation included laboratory corrosion experiments in artificial seawater and the immersion of samples in a marine environment in Attica, Greece, for varying durations. The research indicates that an antifouling coating applied to naval steel in an artificial seawater solution improves corrosion resistance by more than 60%. The conductive polymer covering, comprising polyaniline and graphene oxide, diminishes corrosion current values, lowers the corrosion rate, and enhances corrosion potentials. The impedance parameters exhibit analogous behavior, with the coating preventing water absorption and displaying corrosion resistance. The coating serves as a low-permeability barrier, exhibiting exceptional durability for naval steel over time, with an operational performance up to 98%. Full article

Marine biofouling, the process of marine microorganisms, algae, and invertebrates attaching to and forming biofilms on ship hulls, underwater infrastructure, and marine equipment in ocean environments, severely impacts shipping and underwater operations by increasing fuel consumption, maintenance costs, and corrosion risks, and by threatening marine ecosystem stability via invasive species transport. This study reports the development of a hydrogel-metal-organic framework (MOF)-quorum sensing inhibitor (QSI) antifouling coating on 304 stainless steel (SS) substrates. Inspired by mussel adhesion, a hydrophilic bionic hydrogel was first constructed via metal ion coordination. The traditional metal ion source was replaced with a zeolitic imidazolate framework-8 (ZIF-8) loaded with 2-(5H)-furanone (HF, a QSI) without altering coating formation. Physicochemical characterization using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), the Brunauer–Emmett–Teller (BET) method, and the diffraction of x-rays (XRD) confirmed successful HF loading into ZIF-8 with intact crystal structures. Antifouling tests showed HF@ZIF-8 enhanced antibacterial inhibition against Staphylococcus aureus (97.28%) and Escherichia coli (>97%) and suppressed Chromobacterium violaceum CV026 pigment synthesis at 0.25 mg/mL (sub-growth concentration). The reconstructed PG/PVP/PEI/HF@ZIF-8 coating achieved 72.47% corrosion inhibition via synergistic anodic protection and physical shielding. This work provides a novel green approach for surface antifouling and drag reduction, highlighting MOF-loaded QSIs as promising additives to enhance the antifouling performance of hydrogel coatings, anti-corrosion performance, and QSI performance for sustainable marine engineering applications. Full article

A hull and propeller biofouling assessment framework is presented and demonstrated using a bulk carrier as a case study corresponding to an operational period of two and a half years. The aim is to support the decision-making process for optimizing maintenance related to hull and propeller cleaning actions. For the degradation assessment, an appropriate key performance indicator is defined comparing the expected shaft power required with the measured power under the same operational conditions. The power prediction models are data-driven based on machine learning algorithms. The process includes feature engineering, filtering, and data smoothing, while an evaluation of regression algorithms of the decision tree family is performed. The extra trees algorithm was selected, presenting a mean absolute percentage error of 1.1%. The analysis incorporates two prediction models corresponding to two different approaches. In the first, the model is employed as a reference performance baseline representing the clean vessel. When applied to a dataset reflecting advanced stages of biofouling, an average power increase of 11.3% is predicted. In the second approach, the model entails a temporal feature enabling the examination of scenarios at different points in time. Considering synthetic data corresponding to 300 days since hull cleaning, it was derived that the fouled vessel required an average 20.5% increase in power. Full article

The extended immersion of ships in seawater frequently results in biofouling, a condition characterized by the accumulation of marine organisms such as barnacles and algae. To combat this issue, the application of anti-fouling coatings to the hull surfaces of vessels has emerged as one of the most effective strategies. In response to the increasing global emphasis on environmental sustainability, there is a growing demand for anti-fouling coatings that not only demonstrate superior anti-fouling efficacy but also adhere to stringent environmental standards. The traditional use of organotin-based self-polishing anti-fouling coatings, known for their high toxicity, has been prohibited due to environmental concerns. Consequently, there is a progressive shift toward the development and application of environmentally friendly anti-fouling coatings. This paper reviews the toxicity and application limitations associated with conventional anti-fouling coatings. It provides a comprehensive overview of recent advancements in the field, including the development of novel self-polishing anti-fouling coatings, low surface energy coatings, biomimetic coatings, and nanostructured coatings, each leveraging distinct anti-fouling mechanisms. The paper evaluates the composition and performance of these emerging coatings and identifies key technical challenges that remain unresolved. It also proposes a multi-faceted approach to addressing these challenges, suggesting potential solutions for enhancing the effectiveness and environmental compatibility of anti-fouling technologies. The paper forecasts future research directions and development trajectories for marine anti-fouling coatings, emphasizing the need for continued innovation to achieve both environmental sustainability and superior anti-fouling performance. Full article

Regular inspections and hull cleanings are essential to prevent bio-fouling on ships. However, traditional cleaning methods such as brush cleaning and high-pressure water-jet cleaning at docks are ineffective in cleaning niche areas like bow thrusters and sea chests. Consequently, cleaning robots based on brushes and water jets have been developed to effectively remove bio-fouling. However, there are concerns that brushes may damage hull coatings, allowing bio-fouling to penetrate the damaged areas. In this study, removal experiments were conducted to identify the most dominant factor in fouling removal using water jet-based cleaning, in preparation for the development of non-contact cavitation high-pressure water jet-cleaning robots. The Taguchi method was used to identify influential factors and generate experimental conditions, and equipment systems for the removal experiments were established. Image analysis was performed to assess the bio-fouling occurrences on each specimen before and after cleaning, and numerical simulations of the nozzle were conducted to estimate stagnation pressure and wall shear stress to confirm the effect on micro-fouling removal. The results indicated that pump pressure is the most influential factor in removing large bio-fouling organisms grown in marine environments and on ship surfaces. Full article

Traditional anti-corrosion and anti-fouling coatings struggle against the harsh marine environment. Our study tackled this by introducing a novel dual-layer hydrogel (A-H DL) coating system. This system combined a Cu₂O–SiO₂–acrylic resin primer for anchoring and controlled copper ion release with a dissipative double-network double-anchored hydrogel (DNDAH) boasting superior mechanical strength and anti-biofouling performance. An acrylamide monomer was copolymerized and cross-linked with a coupling agent to form the first irreversible network and first anchoring, providing the DNDAH coating with mechanical strength and structural stability. Alginate gel microspheres (AGMs) grafted with the same coupling agent formed the second reversible network and second anchoring, while coordinating with Cu²⁺ released from the primer to form a system buffering Cu²⁺ release, enabling long-term antibacterial protection and self-healing capabilities. FTIR, SEM, TEM, and elemental analyses confirmed the composition, morphology, and copper distribution within the A-H DL coating. A marine simulation experiment demonstrated exceptional stability and anti-fouling efficacy. This unique combination of features makes A-H DL a promising solution for diverse marine applications, from ship hulls to aquaculture equipment. Full article

Biofilms, complex microbial communities, adept at forming on diverse surfaces within environments, such as membrane technologies, ship hulls, medical devices, and clinical infections, pose persistent challenges. While various biofilm prevention methods, including antimicrobial coatings, physical barriers, and bacteriophage utilization, have been devised for engineered systems, their efficacy fluctuates based on application type and microbial species. Consequently, there remains a pressing need for the development of highly targeted and efficient biofilm control strategies tailored to specific applications remains a pressing need. In our investigation, we disrupt microbial cell-to-cell communication in Pseudomonas aeruginosa through the application of anti-quorum sensing (anti-QS) furanone C-30 molecules. The incorporation of these molecules onto electrospun surfaces yielded substantial reductions of 69% in petri dish assays and 58% on mixed cellulose ester (MCE) membranes in a dead-end nanofiltration system, showcasing the potent anti-biofouling impact. Notably, the functionalization of MCE surfaces with anti-QS molecules resulted in a remarkable 16.7% improvement in filtration output. These findings underscore the potential of this targeted approach to mitigate biofilm formation, offering a technical foundation for advancing tailored strategies in the ongoing pursuit of effective and application-specific biofilm control measures. Full article

The biofouling of marine structures must be controlled if crippling operational and maintenance costs are to be avoided and biological invasions prevented. However, traditional methods of biofouling control typically involve the use of toxic chemicals, which have their own drawbacks, both financial and environmental. For ships, the hull is the largest surface requiring a fouling-control coating; however, there are other so-called ‘niche’ areas (up to 10% of the total wetted area) that typically cannot be, or are not routinely, treated to prevent biofouling accumulation. The use of UV light is a tried and tested sterilization method that has been shown to also work underwater. However, the speed with which UV can be applied to large-scale biofouling control will be determined by the engineering challenges involved and the lack of basic understanding of the biological mode of action. The former is essential for the effective translation of this established technology into a high-performance, industrially useful fouling-control system. The latter will be important for environmental regulation and safe use as well as performance optimisation. Here, we developed two bespoke flow-through systems to replicate ship niche areas and deployed them in Melbourne, Australia, and North East England. We demonstrated a 40–90% reduction in biofouling coverage on silicone tiles embedded with UV-emitting LEDs, even as the LED output waned (after ~8000 h). Image analysis and amplicon sequencing of 18S genes provided complementary information about the taxonomic composition of the fouling communities and highlighted some taxa, for example, ascidians and diatoms, which may have, or in the future develop, UV resistance. Interestingly, the UV treatment far exceeded performance estimates based on the predicted attenuation distance of UV in seawater. Overall, while it is clear that UV treatment works in terms of its efficacy against the vast majority of observed fouling species, technical challenges remain, as do knowledge gaps surrounding the biological and ecological effects of widespread use. Full article

The adhesion of marine-fouling organisms to ships significantly increases the hull surface resistance and expedites hull material corrosion. This review delves into the marine biofouling mechanism on marine material surfaces, analyzing the fouling organism adhesion process on hull surfaces and common desorption methods. It highlights the crucial role played by surface energy in antifouling and drag reduction on hulls. The paper primarily concentrates on low-surface-energy antifouling coatings, such as organic silicon and organic fluorine, for ship hull antifouling and drag reduction. Furthermore, it explores the antifouling mechanisms of silicon-based and fluorine-based low-surface-energy antifouling coatings, elucidating their respective advantages and limitations in real-world applications. This review also investigates the antifouling effectiveness of bionic microstructures based on the self-cleaning abilities of natural organisms. It provides a thorough analysis of antifouling and drag reduction theories and preparation methods linked to marine organism surface microstructures, while also clarifying the relationship between microstructure surface antifouling and surface hydrophobicity. Furthermore, it reviews the impact of antibacterial agents, especially antibacterial peptides, on fouling organisms’ adhesion to substrate surfaces and compares the differing effects of surface structure and substances on ship surface antifouling. The paper outlines the potential applications and future directions for low-surface-energy antifouling coating technology. Full article

Biofouling is a universal problem in the marine environment. Static structures and niche areas on ships, such as propellers, are not protected sufficiently by antifouling coatings. Encapsulation has previously been used as a fouling mitigation technique via application of an impermeable wrap or bag to a fouled hull or structure when it arrives in port or on station. This experiment investigated the use of a novel semipermeable encapsulation to proactively protect propeller mimics from biofouling. Sleeves were installed over propeller mimic panels and deployed in an active, multiuse port for 20 months. The sleeves completely prevented macrofouling on the panels for up to 13 months and maintained surfaces below 5% cover for the entire experimental period. This shows improvement over traditional antifouling without negative impacts on water quality like dissolved oxygen, pH, etc. Full article

Ship biofouling is recognized as a significant pathway for the introduction and spread of invasive organisms. The in-water cleaning of ship hulls generates wastewater that includes antifouling paint residues and biofouling organisms, which inevitably leak into the marine environments, resulting in substantial adverse effects on marine ecosystems. To assess the impact of hull cleaning wastewater (HCW) on microalgae, we conducted microcosm experiments using HCW including attached microalgae. The experiments consisted of a total of 12 combined trials, including the following groups: ambient seawater as a control, the 5% HCW group (HCW), and the 5% HCW + nutrient addition group (HCW+N), conducted at temperatures of 15 and 20 °C, respectively. The Chl. a concentrations in the water column in the control group exhibited maximum values on day 1 (5.24 μg L⁻¹ at 15 °C and 12.37 μg L⁻¹ at 20 °C), but those of the treatments were at low levels, below 2 μg L⁻¹ at both temperatures. On the other hand, the Chl. a concentrations on plastic plates were higher in the treatments than in the control group. Specifically, the Fv/Fm ratio in the water column, which indicates photosynthetic activity, was significantly higher in the control group compared to both the HCW and HCW+N groups at 15 and 20 °C (p < 0.05). This suggests that the growth of water column phytoplankton was inhibited following HCW inoculation. However, there were no significant differences in the Fv/Fm on plastic plates between the control and HCW treatment groups, implying that the periphyton maintained a high photosynthetic capacity even in the presence of HCW treatments. The elution of particulate copper in HCW was observed, which was considered as the main reason for the growth of phytoplankton. Our study results suggest that the runoff of HCW in the marine environment has a greater negative effect on phytoplankton than on periphyton, which can lead to changes in microalgae community composition and a decrease in productivity in the marine environment. Therefore, it is crucial to manage HCW runoff based on scientific assessments to minimize the ecological risks associated with the removal of biofilm or slime from ship biofouling during in-water hull cleaning. Full article

It is well known that biofouling increases a ship’s resistance and nominal wake. For submarines, any change to the circumferential variation of the nominal wake in the propeller plane will affect the variation of the flow over the propeller blade, and hence the fluctuating forces, and noise, generated by the propeller. The ANSYS FLUENT commercial Reynolds-Averaged Navier Stokes Computational Fluid Dynamics solver was used to investigate the influence of both the longitudinal and vertical distribution of biofouling on the resistance and wake, including the circumferential variation of the nominal wake, on a submarine, using the well-known Suboff standard submarine. For the present work, the k-ε turbulence model was selected, as this is commonly used in this field and is generally considered acceptable. To handle different boundary layer thicknesses in the flow fields, the whole y+ formulation was employed, enabling automatic switching between low and high Reynolds boundary wall models. The numerical solver used for the simulations is based on the finite volume method, which discretizes the RANS equations. In this approach, a segregated model was utilized in the solver, and the convection terms were discretized using the second-order upwind scheme to enhance solution accuracy. The criteria for the near wall are between 30 and 100, and the value of y+ for the present case is 84. It is shown that fouling over only the forward third of the submarine results in a greater increase in resistance than fouling over only the aft third. Fouling over only the lower half of the submarine results in greater resistance than fouling over only the forward third, but less than fouling over the whole of the hull. Fouling over only the forward third of the hull has less influence on the circumferential variation of the wake than fouling over the aft third only of the hull. The results show the importance of keeping the forward area of the hull clean when considering resistance only, whereas keeping the aft area of the hull clean is important when considering the uniformity of the nominal wake into the propeller. Full article

Biofouling is a significant means for introducing non-indigenous marine species internationally, which can alter habitats and disturb marine ecosystems. This study estimated the flux of ships’ wetted surface area (WSA) to Korea in 2020 to assess the risks of biological invasion via biofouling on ships’ hulls. The annual total WSA flux entering Korea was estimated to be 418.26 km², with short-stay vessels (<3 weeks) contributing to 99.7% of the total WSA flux. Busan and Ulsan ports were identified as the main sources of high-risk flux, with container ships being a major vector in Busan and tankers in Ulsan. Gwangyang port had the third-highest total WSA flux, with nearly half of the flux driven from coastwise voyages, making it particularly vulnerable to the spread of hull fouling organisms. These findings could help enhance the management and inspection of hull fouling organisms in Korea. Full article

Fouling organisms reduce a ship’s fuel efficiency and disturb the ecosystem. Therefore, the International Maritime Organization (IMO) and many nations have enacted laws that mandate periodic hull cleaning for removing fouling organisms. However, cleaning niche areas of the ship hull is extremely difficult. Due to their complex shape, applying antifouling paint and cleaning with hull cleaning robots is difficult, but about 80% of fouling organisms are concentrated in the niche areas. To resolve this issue, this research proposes the use of an autonomous cleaning robot with a hydraulic polyarticular robot arm to clean niche areas of the ship hull. This robot can approach niche areas of the ship hull with complex shapes using its polyarticular arm. It was designed to be able to scan the cleaning area, establish a cleaning plan, and clean accordingly. This robot autonomously cleaned a propeller blade, which is a typical niche area of the ship hull, to verify the applicability of this system. The experiment results show that approximately 80% of the biofouling was removed from the hull crevices and 81% of the cleaned biofouling was recovered. Full article