A generic approach predicting the effect fouling control coatings on ship performance

Mehmet Atlar

Based on the past and current research within his groups in Newcastle and Strathclyde Universities, the author presents a generic approach, which is based on the combination of an experimental and computational procedure, to predict the effects of modern days antifouling systems on ship performance "in-service" conditions. The proposed approach is generic and hence can be applied to any ship type and hull coating system in the presence of biofouling and it may even be combined with passive drag reduction systems. The basis of the approach for practical performance estimations is the combination of experimental data collected from flat test panels with representative surface finishes and the extrapolation of this data to full-scale. However, the extrapolation procedure needs to be replaced with Computational Fluid Dynamics (CFD) methods, especially for deteriorated hull surfaces due to fouling, for more accurate and direct estimation of performance prediction in full-scale while the experimental data are still required. The rational nature and hence strength of the proposed approach is to represent the effect of the actual hull surfaces "in-service" by using the state-of-the art experimental methods and data. This provides the option of the extrapolation procedure for practical performance estimations and also enabling the use of CFD methods by avoiding the most difficult barrier of describing the actual hull surface numerically in CFD for more accurate performance estimations.

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Marine antifouling and fouling release coatings: the key parameters controlling their performances

Christine Bressy

Marine biofouling is a worldwide problem, costing billions of dollars per year in civil and military marine applications. For the marine shipping industry, biocides-based coatings and Fouling Release Coatings (FRCs) are current strategies used to prevent and control the natural process of colonization of ship hulls. On the one hand, biocides-based coatings which are leaders on the market are under the European biocidal product regulation. Their antifouling efficiency over time depends on a constant biocide release rate. Key parameters such as the type of the matrix, the speed of the ship and the seawater properties could affect their efficiency. On the other hand, FRCs increase recently their market share based on their long-term efficiency not only on moving structures but also on static ones. Most of FRC systems are biocide-free systems with a lower environmental impact. Key parameters including surface roughness and thickness of the coating but also application procedures affect their overall performance. Users, paint applicators or providers have all to be aware of the key parameters which govern the long-term efficiency of marine antifouling and fouling release coatings.

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Drag characteristics of newly applied marine coatings and potential applications in combination with ultrasonic devices

Maxim Candries

This presentation discusses an experimental investigation conducted at the Emerson Cavitation Tunnel (ECT) of Newcastle University to investigate the boundary layer and surface roughness characteristics of three commercially available hull coatings: a tin-free SPC, a new generation Foul Release coating and a novel nanostructured coating. In addition, two coatings that have been artificially roughened by mixing in sand grit during application were included in the study. These coating were roughened in order to mimic either hull surfaces that have been a while in service or poor quality coating applications.

In order to examine the boundary layer characteristics of the coatings, a large flat plane model with interchangeable test sections was used. A two-dimensional DANTEC Laser Doppler Velocimetry (LDV) system was used to collect the boundary layer data of each coating.

The measurements provided critical parameters including local skin friction coefficients and roughness functions. The surface roughness of the tested coatings was analysed using both a non-contact laser profilometer and a stylus instrument.

The tests and subsequent analysis allows to compare the hydrodynamic performance of these antifoulings. The measured boundary layer data were analysed by using different analysis methods to predict and compare the skin friction characteristics of these coatings.

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Inspection by drones

Peter Everaardt

The timely detection and continuous monitoring of corrosion is essential for protecting your assets. Regular inspection saves money and increases safety. With the help of drones you can inspect cost-effectively. This uniquely combines with reducing risks of human injuries as a result of accidents provoked by working at height.

Available methods of inspection, visual as well as thermal, give companies the opportunity to build data management systems for monitoring assets. Drones carry cameras to acquire necessary data.

In the future new technologies like Artificial Intelligence and machine learning will help predict the wear and tear of structures. Drones will be instrumental in applying such pioneering techniques.

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Is there a future for biocide containing anti-fouling coatings? A regulatory perspective

Linda Jones

In the midst of other global regulatory schemes for biocides, the European Union's system is one of the most comprehensive: its changes are followed by other regions, its effects are felt worldwide. Other government competent authorities have studied Europe's advancements as an example, but also the global antifouling paint industry has closely watched the developments, with its product portfolio in mind.

Initially, the attention was focused mainly on the evaluation of existing antifouling active substances, most of which have now finally passed their initial regulatory review. It is hopeful to see that some new active substances for antifouling Product Type 21 have appeared on the scene which have actually made it through most of the regulatory hurdles. Considering also the 'mid-term' legislative changeover from the BPD (Biocidal Products Directive 98/8/EC) to the BPR (Biocidal Products Regulation (EU) No. 528/2012) this is a major achievement.

All-in-all, however, the European regulatory process has thinned out the active substance arena with a reduced choice for paint formulators as the overall outcome. The past 20 years have shown that the biocides arena is like "Running the Gauntlet", requiring companies to build stamina and be pretty agile. Believe it or not: the effects of those 20 years are only just reaching the marketplace. And what about new developments?

This presentation looks at the regulatory process for antifouling biocides and its complications and challenges. It tries to provide food for thought for the following questions:

Whatever the answers, past or even current performance are not necessarily a guarantee of future results. Nonetheless, it is time to learn from the regulatory process until now, for new initiatives to have a better chance to succeed.

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UVC based biofouling prevention solutions for ship hulls

Michel Jongerius

AkzoNobel and Philips are jointly developing a fouling prevention solution based on UV-LEDs (RunWell®). This innovative concept is based on the transport of UVC light, which is generated by LEDs embedded inside a multilayer film system. The outer surface of the film is irradiated with the UVC light, thus preventing fouling settlement. The design of the device is informed by optical simulation based on input of optical material and LED properties, device geometry and knowledge on the minimum UVC threshold intensity required for fouling prevention. In this presentation, we will provide experimental data from successful in-field fouling prevention tests ranging from those conducted in collaboration with DST Group (Australia) and FIT (US) to the first in-service trials of the concept on ocean going vessels. The most recent insights and advances towards achieving a new prototype generation with increased tile size (0.5x0.5m2) and decreased thickness (4mm) are presented, as well as the technology enablers of the device concept, e.g. the optics approach, the UVC LED technology, the powering solutions, and the mechanical design.

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Microbial influenced corrosion in maritime environment

Job Klijnstra

MIC is the deterioration of metals as a result of metabolic activity of microorganisms. Different genera of microorganisms convert nutrients which are available in soil and water into acids and other corrosive by-products which change (local) environmental conditions and may accelerate corrosion processes.

Due to the complexity of MIC many cases are misdiagnosed or ignored. 20% of all corrosion related damage cases are of microbial origin. In reality the number is much higher because often this type of corrosion is overlooked during failure analysis. However, the diagnosis is difficult and is based on a case-by-case approach. A combination of different fields of knowledge e.g. microbial analysis, failure analysis, metallurgy and electrochemistry makes a thorough and reliable diagnosis possible. It needs not only to be proven that microorganisms are present but also that they are active at the affected structure. Often conclusions are made too fast so that MIC is diagnosed while a different corrosion mechanism is present.

The reason that MIC is present in many different systems is that microorganisms are resistant to or tolerate a broad range of conditions with regard to temperatures, pH, pressure or oxygen content and that they are able to adapt quickly in changing environments. MIC can be recognized very well by its typical tubercles or corrosion products, being relatively soft layered structures consisting of orange iron hydroxide products and black products containing iron sulfide. These layers are only weakly attached to the steel surface and underneath the steel is shiny with pits, craters and holes.

In this presentation a number of MIC cases will be presented to show the complexity of proper MIC diagnosis and the possible relationship with other corrosion processes that may play a role.

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Maritime corrosion - New insights

Rob Melchers

Corrosion in marine environments continues to remain a critical issue for the effective life of expensive assets such as ships, offshore structures, pipelines, tunnels and bridges. Detection of rust often raises alarm but is this always justified? To throw some light on this question it is necessary to understand some of the fundamental engineering-science aspects of corrosion. While electro-chemistry underlies the fundamental aspects of corrosion, it bears little relationship to practical matters, in the same way that atomic physics tells us little about how to proportion and design a major structure such as a bridge. Nevertheless understanding of fundamentals, and in particular the mechanics involved in differential aeration, pitting and crevice corrosion and the role played by rusts are important to understand the development of corrosion with time, and the regions where corrosion is likely to be most significant. The basics of these are outlined, developed into mathematical models that can be applied to predict corrosion loss and also pit depth, all as functions of environmental characteristics such as temperature, oxygen availability, water velocity and nutrient pollution. The latter has been shown to be a critical factor in the prediction of corrosion induced by microbiological activity (microbiologically influenced corrosion - MIC). It can lead to severe corrosion, usually highly localized. However, there are other conditions that can cause highly localized corrosion, and it would be a mistake to attribute it to MIC, as is commonly done.

Most attention will be given to mild and low alloy steels as these tend to corrode in a similar way, with detours to corrosion at welds, on old cast irons, including those buried in the ground, marine corrosion of stainless steels, and of copper-nickels and aluminium. Some comments will be made also about corrosion in freshwaters and in deep ocean conditions. A number of actual examples will be described, including corrosion of mooring chains and inside ballast tanks, and of sheet-piling walls, cast iron bridge piers and oil industry water injection pipelines.

An outline will be given of the current projects on ship behaviour including effects of fatigue and corrosion, the corrosion inside wind turbine towers, corrosion of steels on and within marine sands and the long-term corrosion of cast iron water supply pipes buried in soils. Most recently we have been investigating the corrosion of mooring chains exposed for some 100 years in Pacific Ocean coastal seawaters.

Finally, some comments are made about protection systems, including protective coatings, impressed current cathodic protection and sacrificial anode cathodic protection, and also about the potential use of corrosion inhibitors. In assessing the potential of these systems it is very helpful to understand the basic idea that corrosion is ultimately driven by differential aeration and thus pitting at some scale, and the importance of rusts and their composition. Practical matters such as surface preparation arise naturally from such understanding.

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Environmental risks related to munition dumped at sea: case study from the Paardenmarkt dumpsite off the Belgian coast

Tine Missiaen

The Paardenmarkt is one of the many munition dumpsites in our seas and oceans. However, its magnitude and location - just one mile off the densely populated Belgian coast and close to a major harbour- make it a huge challenge in terms of management. A few metres below the seafloor, ca. 35.000 tons of conventional and chemical munition from WW1 are buried, containing chemicals like mustard gas, phosgene and Clark (an arsenic compound). Next to these chemicals, the munition contains a large amount of explosive and likely also propellant material. To this day, the site was left undisturbed and was monitored with regular intervals. However, past research has been fragmentary, and a lot of uncertainties still remain today regarding the physical, biological, chemical and toxicological characteristics of the site.

Magnetic data provide a good overview of the horizontal distribution of the munition, but their burial depth remains poorly known (estimated between 2 and 5 m). Little is also known about the state of the munition. Shells recovered in the early 1970's were "in a remarkable good condition", but since then the munition has become buried and regulations have prohibited new recoveries. Experimental studies and modelling are needed to assess the effect of different corrosion processes (aerobic/anaerobic, galvanic, microbiological, chemical), but also the ageing of explosives and propellant material in seawater and the effect of sand and water on the explosive effect of the buried munition.

Current monitoring involves conventional chemical analysis of seabed and water samples. Recent studies however suggest that the migration of toxic compounds in the sediment is very limited. Precise in-depth sampling is crucial for any reliable assessment of leakage. The toxic warfare agents at the Paardenmarkt differ from those encountered at most other (WW2) dumpsites, and real information on dose-response relationships from the compounds and their degradation products is very limited. Innovative sampling and measurement techniques combined with sediment migration tests are needed to model the ecotoxicological and human health risks, and assess the potential of microbial degradation.

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Exploring the mechanisms of biocorrosion and putting them to use in novel applications

Jo Philips

Microorganisms cause biocorrosion through various mechanisms. Recent microbiological investigations demonstrated that some microorganisms are capable of withdrawing electrons directly from steel (i.e steel as electron donor or 'food' for the microorganisms), which strongly increases corrosion in comparison to abiotic conditions. In this presentation, I will explain how I isolated novel biocorroding strains and which insights I obtained into their corrosion inducing mechanisms.

The remarkable property of microorganisms to withdraw extracellular electrons does not only have negative effects (e.g. biocorrosion), but can also lead to novel biotechnological applications. I will explain why biocorroding microorganisms are of interest for microbial electrosynthesis, i.e. a process in which microorganisms utilize extracellular electrons (delivered by an electrode) for chemical conversions. This process could be highly valuable for the storage of excess electric energy, as well as the conversion of CO2 into biofuels or biochemicals.

OCEANIC PROJECT: Brief presentation of the project and the results

Emiliano Pinori

Engineered structures operating in or near the marine environment are subject to one of the most aggressive environments for material degradation, such as corrosion, erosion, and last but not least marine biofouling, the attachment and growth of undesired organisms on the exposed surface. Corrosion and biofouling are major problems shared among all the structures immersed in seawater. Structures requiring protection include ships, docks and buoys, oil & gas rigs and the emergent ocean renewable energy sector, including wind, wave and tidal generation systems.

The OCEANIC project aims to develop new protective coatings for marine applications, by combining two technologies, namely the well-established thermal sprayed aluminium (TSA) coatings for corrosion protection and a novel antifouling technology based on low emission of highly potent biocides. The primary goal is to produce an all-in-one coating with a life-time of >10 years and consisting of a porous TSA coating in which polymer containing biocide has been incorporated during the coating process. The expected impact will be higher material reliability and increased lifetime of constructions in the Ocean Energy sector.

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The predictability of corrosion

Olivier Schalm

The corrosion process of metals is an extremely complicated phenomenon that is heavily studied. Despite the millions of publications about this topic and our extensive knowledge it remains difficult to estimate the risk for enhanced corrosion rates in certain environmental conditions. The values and trends of environmental parameters (e.g., water temperature, salt concentration, etc.) only give an impression of that risk. This contribution will demonstrate that it is possible to convert environmental measurements in a risk measure by using several principles.

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Shipping with nature

Jan Seys

The last few decades, our mindset is changing in the way coastal inhabitants face the ocean and the treats of climate change and sea-level rise. As a matter of fact, on the border of land and sea, fighting nature has evolved more and more into "building with nature", an approach that has proven to be cost-saving, more environmentally friendly and often as effective as conservative solutions. This more flexible attitude, in line with what the ecosystem is providing us in terms of services and products, often turns out to be mutually beneficial.

The same applies to shipping and how it relates to the ocean realm and human beings. Where seafarers in one way or another have always felt deeply connected with the blue salty part of our planet, the way shipping and ocean life are interconnected is about to change. Anti-fouling, corrosion prevention, fuel & fuel consumption, fighting marine debris, etc are just a few examples of how the maritime sector is invited to the paradigm of "shipping with nature" instead of fighting nature. In this presentation the author will shed light on this delicate interaction between mankind and ocean ecosystem services from a wider perspective.

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Mechanisms and potential monitoring approaches for Accelerated Low Water Corrosion (ALWC) of marine structures

Martin Smith

Accelerated Low Water Corrosion (ALWC) is a microbially influenced corrosion phenomenon with reported corrosion rates 5-10 times normal electrochemical corrosion rates. It has been extensively reported from steel pilings in harbour environments, causing failures and hence a major economic impact on coastal infrastructure. Given its occurrence in the intertidal and splash zone it also has the potential to occur on other marine structures with corresponding impacts on structural integrity. Work at the University of Brighton, joint with Shoreham Port Authority, UK, has identified the mechanism of ALWC, identified the role of the marine environment as a source reservoir for the corrosion causing bacteria, and pioneered rapid microbiological and mineralogical criteria for identification. Combined metagenomic analysis and X-ray photoelectron spectroscopy has demonstrated the role of sulphate reducing bacteria against the steel surface, protected from the oxic marine environment by consortia of sulphur and iron oxidising bacteria which generate a range of reactive, intermediate oxidation state, sulphur compounds. Analysis of bed sediment and of the water column has demonstrated these bacteria occur in anoxic marine sediment, and are not introduced from elsewhere. High resolution melt (HRM) analysis of DNA, and Fourier Transform Infra-red (FTIR) spectroscopy of corrosion products have proved effective in identifying consortia of ALWC causing bacteria and differentiating ALWC from typical marine corrosion respectively. Monitoring of environmental parameters over an 18 month period indicates both harbour bed anoxia reaching from sediment pore water into the water column during summer months, and sediment resuspension resulting in increased turbidity during port activity as potential vectors for the transmission of sulphate reducing bacteria from sediment to structural steel. The former suggests bed sediment anoxia, water temperature and nutrient supply may be risk factors for ALWC. The use of rapid microbiological (HRM) and spectroscopic techniques suggests potential new routes for monitoring and early stage identification of ALWC issues.

Corrosion monitoring - Insights from the Offshore Renewable Energy sector

Jeroen Tacq

Corrosion of steel assets can incur significant O&M costs. Traditional corrosion management procedures involve periodic inspections to detect the corrosion state of an asset. By knowing the corrosion state on a number of discrete points in time, estimates of corrosion rates can be made. Extrapolation into the future allows to define a maintenance schedule, while critical failures detected during inspection need to be remedied immediately. This traditional method of corrosion management practice is generally accepted, however, technological advancement creates opportunities for a different approach.

There are a number of relevant questions with respect to the classical approach. What happens between inspections? Are there fluctuations in corrosion rate that remain undetected? What if there is a failure that remains undetected until the next inspection? What about health and safety issues for inspectors? How to reduce risk/cost related to inspection of difficult to reach zones? It is possible to address these and other questions by applying continuous corrosion monitoring?

The European NeSSIE project revealed that more and more Offshore Windfarm owners are looking into the possible added value of corrosion monitoring. The goal of NeSSIE is to transfer knowledge from other sectors to the Offshore Renewable Energy (ORE) sector. However, on this particular topic, there may be an opportunity to also transfer knowledge the other way around. Corrosion monitoring of ORE structures is still in its infancy and manual inspection will likely remain necessary in the near future. Still, a number of lessons have already been learned in a search for the economic potential of corrosion monitoring. By sharing what the ORE sector's experiences and inviting the maritime sector to do the same, further development of the potential benefits of continuous monitoring may be accelerated.

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Saline resistant weathering steel for offshore and naval: corrosion testing and characterisation?

Krista Van den Bergh

Weathering steels are mild low-alloy steels with a carbon content of less than 0.2 wt% and alloying elements (Cu, Cr, Ni, P, Si and Mn) to a total of a few per cent (3-5 wt%). The enhanced corrosion resistance of weathering steel is attributed to the formation of a dense and well-adhering corrosion product layer, known as patina. Depending on the application and environmental conditions, weathering steel is used in unpainted or painted state. Protection of steel structures against corrosion in offshore environments is a challenging task compared to rural or industrial environments, mainly due to the harsh conditions induced by the high load of chlorides in the seawater and the atmosphere. Conventional weathering steel, like e.g. Indaten or Corten, which is frequently used in urban and industrial areas, does not form a protective patina in chloride rich environments. The main reason for this is the instable behaviour of oxides in the presence of chlorides with the fast diffusion of chloride species through pores in the rust layer. Therefore, it has a very limited use in coastal areas and it is not used for offshore applications.

In order to reduce the life-cycle costs of large offshore structures, the development of a cost-effective corrosion-resistant steel substrate, which would in fact need no coating at all, would be a step forward. Target applications would be topside painted steel structures, e.g. fixed and floating platforms, offshore wind towers and substations.

To predict the long-term outdoor corrosion behaviour in offshore conditions, it is important to define accelerated corrosion tests with conditions close to the natural outdoor conditions. Outdoor, natural exposure give real exposure behaviour but they are expensive and time consuming. Therefor there is a need for accelerated corrosion tests (ACT) that will simulate the conditions of saline offshore conditions. In this work accelerated corrosion tests with alternating wet and dry periods are developed. Since the enhanced corrosion resistance of weathering steel is attributed to the formation of the patina, an in-depth characterization of the rusts formed after accelerated tests is performed by advanced surface analytical tools.

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Applied coating thickness ranges in ballast tanks placed next to the PSPC requirements

Remke Willemen

Ballast tanks are prepared and coated according to the IMO Performance Standard for Protective Coating regulations (PSPC15), taking into consideration the paint application requirements of the paint producer. In general, it can be stated that a nominal total dry film thickness (NDFT) of 320 µm is put forward taking into consideration the 90/10 rule, using a light-colored epoxy coating, with the advice to use minimum two spray coats on flat surfaces. Allegedly this PSPC rule is sometimes misinterpreted as a benchmark of 320 µm on the so called flat surfaces, resulting in a non-PSPC compliance as it appears that there exists a big variation in coating thicknesses on the flat surfaces of one single ballast tank. Taking a closer look, considerable variations may even be noted on surface area patches of 50 x 100 mm. This study indicates that the average in-situ NDFT appears to be 500 µm and that extreme thickness variations were noted in the field, namely below 288 µm and above 800µm. The impact of the coating performance of ships with ascertained extreme low and high thicknesses appears to be negatively deviating from the average ballast tank performance. Even coatings with minimum thickness values between 288µm and 320µm appear to have a negative impact. We conclude that it should be emphasized that the PSPC15 requirement is a paint system framework description. In respect of paint application, the requirement can be broadened to include an average DFT as a paint applicator benchmark together with a clearly specified minimum and maximum DFT, in order to avoid any misinterpretations.