Query: thickness required to coating marine structures

title: Methodology of calculating required chloride diffusion coefficient for intended service life as function of concrete cover in reinforced marine structures
abstract: For marine reinforced concrete (RC) structures, chloride initiated corrosion of reinforcement is generally accepted as the service life limiting degradation mechanism. A methodology is described for how the maximum required chloride diffusion coefficient (D) of a concrete for achieving an intended service life (t) can simply be calculated as a function of concrete cover thickness (x) over the reinforcement by D constant*x 2 /t. The principle is based on the usual mathematical solution to Fick's 2nd law of diffusion. The constant is broken down into 3 factors; chloride concentration factor, aging factor and temperature factor, in which input parameters have to be selected. These factors are calculated for a range of selected input parameters illustrating their sensitivity. The largest uncertainty lays in proper selection of the aging factor of the diffusion coefficient. Some concrete recipes satisfying estimated chloride diffusion coefficients are proposed as part of the methodology.

title: Evaluation of coating resistivity for pigmented/unpigmented epoxy coatings under marine alternating hydrostatic pressure
abstract: To realize a rapid evaluation of coating degradation under alternating hydrostatic pressure (AHP) appropriate physical models of electrochemical impedance spectroscopy (EIS) data fitting were respectively developed for epoxy coatings with and without pigments, based on their different water absorption behaviours. Power law model was selected to evaluate the anti permeability of epoxy varnish (EV) coating, which tends to form through pores in the coating structure. On the other hand, two layer model based on Young theory was developed to evaluate the anti permeability of pigmented epoxy coating. Consequently, the resistivity profile with coating thickness was calculated as a critical parameter to describe the anti permeability of coating at different immersion time. The interpretation of water diffusion dynamics based on different coating structures was also given, which is responsible for the choice of distribution models.

title: Antifouling studies and coating strategies for marine deployed structures
abstract: Biofouling represents a real technical challenge in the marine environment. Current antifouling strategies offer insufficient protection from biofouling for many applications, e.g. water sensing technologies, and effective novel methods of antifouling are required to support technology developments in the marine. Non toxic approaches to antifouling are desirable; however, further development of effective non toxic antifouling materials requires a greater understanding of the interaction between a biofouling organisms and a surface. At present, there is a lack of agreement regarding the influence of surface surface texture on microbial behaviour at a surface. Surface texture and roughness has been reported to both negatively and positively affect biofouling organism recruitment to a surface. However, it appears that the response can vary with both organism and adhesion mechanisms, and nature of the coating or surface texture. These parameters influence the surface area available to a settling cell during early biofilm formation, the adhesive strength of a cell to a substrate, and direction of local hydrodynamic forces, the local chemical nature of the substrate and accumulation of organic matter on the surface. Surface topography encountered by a settling organism or propagule is also dynamic and changes with the length of immersion and size and abundance of previously adhered cells. Further investigation of the potential to optimise surface coatings for reduced biofouling of surfaces is required. This work demonstrates the deployment of several novel materials with different chemical characteristics that have the potential to reduce biofilm formation on sensor surfaces and to aid in sensor maintenance. The deployments are carried out over a number of months in Dublin bay using multiple panel platforms to facilitate removal for biofilm characterisation intermittently.

title: Coating Breakdown Analysis of Steel Plates in Marine Structures
abstract: The objective of the present study is to analyse the coating breakdown of steel plates in marine structures, subjected to uniaxial in plane compression. A finite element model is developed and validated in ANSYS. The behaviour of the coated steel plate, with an initial imperfection and a macro delamination in the interface, is studied based on the eigenvalue buckling and nonlinear strength analysis. The compressive loads acting on the plate, in addition to the initial imperfections caused by the inadequate steel surface preparation and/or poor coating application, leads to the local buckling of the coating layer. As the load increases the buckled region increases reaching the critical size, when the coating layer starts to delaminate. Based on the exponential form of the cohesive zone model, a zero thickness interface element, to model the adhesion between plate and coating layer, is employed. When the stress in these elements exceeds the critical one, the stress field is redistributed, resulting in the element deformation and separation/delamination across the interface. The influence of the delamination length, coating thickness, mechanical and interface properties on the buckling and post buckling behaviour of the steel plate coating are also studied. Based on these results, a coating failure assessment diagram for the macro delamination diameters is created.

title: Bio inspired protective structures for marine applications.
abstract: Materials and structures for marine applications are often required to combine high mechanical performance with lightness, but traditional solutions are not always adequate to the scope. The application of biomimetic science could provide innovative and efficient solutions, whose research is the aim of the present paper. In the current work, bamboo samples were subjected to impact both on the outside and on the inside surface. It was found that the impact strength is correlated to the third power of thickness and that the softer inside layers may act as an energy absorbing structure, which enhance impact resistance. Impact tests were also performed on specimens whose outside surface had been abraded and on whole cylindrical sections. The role of graded and hierarchical structure in impact response, suggested some guidelines for bio inspired structures design. Four bamboo inspired structures were designed, based on the idea of combining corrugated panels with different geometrical characteristics to resemble bamboo graded and hierarchical structure. These structures were made using 3D printing and tested in compression. The best performance was obtained by the structure which more closely replicates bamboo's hierarchy. Structure performance could be predicted with reasonable accuracy using buckling theory.

title: Corrosion behaviour of ZrO2 TiO2 nano composite coating on stainless steel under simulated marine environment
abstract: Nano structured ZrO2 TiO2 film coating was realized on AISI 304 stainless steel using the sol gel dip coating technique. The effect of coating on the corrosion resistance of steel was investigated in simulated marine water using potentiodynamic polarization measurement. The effect of coating process parameters on the corrosion rate was systematically investigated using the Taguchi methodology of DoE. The results reveal an appreciable enhancement of as much as 88.21% in corrosion resistance of stainless steel with the additional coating. The morphology, thickness and micro hardness of the coating were found to influence the corrosion resistance.

title: Evaluation of Corrosion Resistance and Characterization of Ni Cr Coated Structure Using Plasma Spray Coating for Marine Hulls
abstract: Corrosion is a natural process which gradually destructs the materials with their environment by chemical or electrochemical means. Mechanized boat hull structures used in fishing were made up of mild steel plate where it corrodes easily within 2 to 6 months due to the marine environment. To prevent this corrosion, coating can be performed on the outer surface of the hull structure. For many decades, the hull structure is made up of mild steel with the thickness ranging from 6 to 20 mm depending upon the usage in marine and structural applications due to its high specific mechanical and thermal properties, However, it corrodes due to the nautical environment and so the paint was coated on the surface, where these paints react with sea water within 6 to 12 months and start corroding the boat hull structure. So, coating with a highly corrosive resistant material in marine environment can be used on the surface of the hull structures to protect from corrosion. Moreover, the partially immersed mechanized boat hull structure and the engine room corrode due to seawater and heat liberated. In the present work, an attempt was made with micro particle coating on the surface of the hull structure to prevent the corroding marine hull structure, thereby enhancing the properties and life of the structures and reduce the maintenance cost leading to economic growth of the fishermen. Ni Cr powder was synthesized using heavy ball milling method and the required size was obtained. The coating was carried out on the surface of the hull structure using plasma spray techniques and the prepared specimens were sized using EDM CNC based on ASTM standards. Various tests like surface roughness, hardness properties (Rockwell, Brinell, Vickers and Micro Vickers) corrosion tests (salt spray and general weight loss method) and characterization using SEM, EDAX, XRD, and FTIR were performed with uncoated, paint coated, and Ni Cr coated surface. The obtained results were compared and it reveals that the utilization of Ni Cr coating enhances the properties of marine structures from the existing metal in use and divulges that this coating reduces the corrosion rate, improves structure life, reduces maintenance cost, reduces the lapses in fishing trips, and increases the economic growth of the fishing community.

title: Marine corrosion resistance of CeO2/Mg(OH)2 mixed coating on a low alloyed steel
abstract: Mixed Mg(OH)2/CeO2 coatings were deposited by cathodic electrodeposition on AISI 4135 steel in order to improve its resistance to marine corrosion. CeO2 coating was first prepared by cathodic electrodeposition in a low concentration of cerium nitrate bath. Then, brucite layer is formed by cathodic polarisation in magnesium nitrate bath. Scanning electronic microscope (SEM) energy dispersive X ray spectroscopy (EDS) X ray diffraction (XRD) and micro Raman spectroscopy (m Raman) analysis were used to study the morphology, chemical composition, microstructure and thickness of the coatings. The corrosion resistance of the coatings was evaluated in artificial seawater by electrochemical methods. CeO2 coating presents a porous and cracked structure; consequently, it offers low corrosion protection of steel in seawater. However, Mg(OH)2/CeO2 mixed coatings have a more uniform and compact structure and present a better corrosion protection of steel in seawater. The protection efficiency of these coatings is then discussed and a protection mechanism is proposed after surface and cross section SEM and m Raman analyses of the coating after several seawater immersion durations.

title: Parametric Study of Ultrasonic De Icing Method on a Plate with Coating
abstract: Ultrasonic de icing is a promising method to de ice structures by using lightweight and simple transducers, with the advantage of low power consumption. A successful ultrasonic de icing technique requires the understanding of the effects of different parameters on de icing. This paper presents a thorough parametric study of the ultrasonic de icing method on a plate with coating. First, the dispersion equations of shear horizontal (SH) and Lamb waves were derived based on the global matrix method. Meanwhile, interface shear concentration coefficients (ISCC) were introduced to represent the ability of ultrasonic de icing, which was further integrated into Lamb wave and SH waves dispersion curves for the selection of optimal frequencies. Second, a three layer plate model (host plate coating ice) was used to demonstrate the effect of different parameters of coating and the thickness of ice on ultrasonic de icing. The theoretical model provided the design principle of coating and ultrasonic parameters required for efficient de icing. Finally, an experiment was conducted on an ultrasonic de icing platform to validate the proposed ultrasonic de icing method. In this process, material parameters including the Young's modulus, thickness of coating, and thickness of the ice layer were analyzed. The trends of power consumption and optimal frequency of experiments are in good agreement with the analytical calculated results.

title: Orthotropic fluid diffusion in composite marine structures. Experimental procedure, analytical and numerical modelling of plates, rods and pipes
abstract: Finite elements simulations of fluid diffusion for composite structures are becoming more common in marine and offshore applications. Input parameters for such simulations are the orthotropic diffusion constants for the materials. Diffusivity in fiber direction is faster than diffusivity in transverse direction; it is therefore important to determine all these constants to predict long term fluid diffusion in composite structures. Current standards for the determination of the diffusion constants prescribe a sample geometry that enforces 1 D diffusion, but thin samples are not easy to fabricate, especially from thick laminates. Edges with metallic coatings are also prescribed, which can influence the calculation of the moisture saturation content and may detach during the experiments. Furthermore, axial symmetrical structures are often used offshore, requiring 3 D diffusion analysis in cylindrical coordinates. The aim of this paper is to provide a 3 D theory and methods for obtaining diffusion constants for plates, rods and pipes.