Structures In Seawater Research Articles

Corrosion and Biofouling Behaviors of Self‐Organized Structures on Steel Surface Fabricated by Femtosecond Laser

Self‐organized ripple and pillar structures are fabricated on steel surface using femtosecond laser. Their wettability is investigated in terms of static contact angle, roughness, and chemical bonds. The pillar structure is treated in low surface energy solution to further improve its hydrophobicity. The corrosion and biofouling behaviors of the structures in sea water are investigated by electrochemical and chlorella immersion experiments, respectively. The results show that the ripple structure is hydrophilic with a static contact angle similar to the original surface, while the pillar structure is highly hydrophobic since it has higher roughness and amount of non polar chemical bonds. The pillar structure is further transferred to superhydrophobic through the low surface energy treatment. The improved hydrophobicity facilitates a better anti‐corrosion and anti‐biofouling behavior, and the superhydrophobic pillar structure exhibits the best performance due to its strongest ability to repel water and chlorella adhesion.

Experimental Investigation of the Effect of a Downstream Square Plate on Vortex-induced Vibration and Galloping of a Square Cylinder

A square cylinder exposed to a fluid flow is regarded as the simplest model of the structures in sea water or air flow, and known to show the Karman vortex induced vibration (KVIV) and the galloping in separate or overlapping ranges of flow velocity. In this study, wind tunnel experiments were performed on the cross-flow vibration of a square cylinder, and effects of a downstream square plate on the vibration were investigated to develop a convenient passive technique for vibration control. The square plate has a side length w equal to the side length of the square cylinder D (= 26 mm) and set downstream with the gap ratio S/D in the range of 0.12 to 2.90 where S is the separation gap. The results show that the square plate has only little influence on KVIV and enhances the galloping, resulting in the lower critical reduced velocity of galloping Ug i.e. the onset velocity of galloping reduced to about half of the isolated counterpart at S/D = 0.98. Most remarkable effect of the downstream square plate is the enhancement of the vibration near the peak velocity of KVIV at S/D = 1.17, which is around five times larger as compared with the isolated counterpart. This may indicate occurrence of the wake-body-interference fluid elastic vibration.

Naturally pre-designed biomaterials: Spider molting cuticle as a functional crude oil sorbent

Diverse fields of modern environmental technology are nowadays focused on the discovery and development of new sources for oil spill removal. An especially interesting type of sorbents is those of natural origin—biosorbents—as ready-to-use constructs with biodegradable, nontoxic, renewable and cost-efficient properties. Moreover, the growing problem of microplastic-related contamination in the oceans further encourages the use of biosorbents. Here, for the first time, naturally pre-designed molting cuticles of the Theraphosidae spider Avicularia sp. “Peru purple”, as part of constituting a large-scale spider origin waste material, were used for efficient sorption of crude oil. Compared with currently used materials, the proposed biosorbent of spider cuticular origin demonstrates excellent ability to remain on the water surface for a long time. In this study the morphology and hydrophobic features of Theraphosidae cuticle are investigated for the first time. The unique surface morphology and very low surface free energy (4.47 ± 0.08 mN/m) give the cuticle-based, tube-like, porous biosorbent excellent oleophilic–hydrophobic properties. The crude oil sorption capacities of A. sp. “Peru purple” molt structures in sea water, distilled water and fresh water were measured at 12.6 g/g, 15.8 g/g and 16.6 g/g respectively. These results indicate that this biomaterial is more efficient than such currently used fibrous sorbents as human hairs or chicken feathers. Four cycles of desorption were performed and confirmed the reusability of the proposed biosorbent. We suggest that the oil adsorption mechanism is related to the brush-like and microporous structure of the tubular spider molting cuticles and may also involve interaction between the cuticular wax layers and crude oil.

Vortex motion due to differential diffusion

Convection caused by the double (differential) diffusion in a rotating medium can lead to a transfer of vorticity, and in particular, to its concentration. In geophysical applications, it is not considered usually, because the spatial and temporal scales of such convection and rotation effects differ greatly – the period of planetary rotation is many orders of magnitude greater than the characteristic time of existence of the corresponding convective structures in sea water. The paper draws attention to the fact that in the atmosphere there are possible the processes, in which a noticeable transfer of vorticity, caused by the difference in the effective exchange coefficients for various substances, seems to be more real. Effects of the type of double diffusion in the air are possible in principle, in connection with some difference in the rates of heat, water vapor and (or) heavy admixture transfer. The simplest linear model of convection due to double diffusion in a rotating medium is considered. The possibility of the contribution of such effects to the concentration of vorticity during the tornado formation is discussed.

Cathodic protection of structures in seawater using solar panels

It is well known that the cathodic protection of structures in seawater is accompanied by the formation of calcareous deposits on them. In current study, we consider the physicochemical modelling of the formation of the deposit composition against cathode current density in seawater. The reliability of the model representations is confirmed by direct experiments. The work also studied the protective properties of the deposits with a different composition for low-alloy steels in natural sea water. It has been shown that the deposits of pure Mg(OH)2and the deposits of CaCO3+ Mg(OH)2had better protective ability against corrosion than the deposits of pure CaCO3. However, the deposits of Mg(OH)2dissolved faster than the deposits of CaCO3and CaCO3+ Mg(OH)2. Theoretical concepts and experiments on the laws governing the formation of the deposits and their protective properties are in complete agreement with each other. This allows to use the obtained patterns in the cathodic protection of structures in sea water using solar panels, forming standard deviations with predetermined protective properties in the daytime.

Hydrochemical Characteristics of the Aral Sea in 2012–2013

The decrease in Aral Sea area, which started in the 1960s, caused considerable changes in the hydrological, chemical, and biological structure of sea water. Regular observations of Aral water chemistry ceased in the early 1990s. There were no observations of the concentrations of biogenic element compounds in water (the so-called “first-day analyses”). During expeditions of the Institute of Oceanology, RAS, in September 2012 and October 2013, integrated hydrochemical observations were carried out, including measuring the concentrations of biogenic element compounds, dissolved oxygen, hydrogen sulfide, and carbonate equilibrium components. An objective of this study was to develop methods of hydrochemical studies under high water salinity (mineralization). In addition to the standard hydrochemical complex, water samples were taken to determine total water mineralization and the concentration of dissolved and suspended metal forms. The results of these studies are given.

Micro-Biologically Induced Steel Corrosion and Corrosion Control in Simulated Marine Environment: Steel Electrochemical Response and Micro-Organisms Viability within Cathodic Protection Application

Micro-biologically induced corrosion (MIC corrosion) is a complex and challenging phenomena, associated with the metabolism of microorganisms. Corrosion resistance, surface properties and overall performance of steel structures in sea water, fresh waters or soil are affected by the inevitable existence of various types of microorganisms. Methods, techniques and practical applications are available, however, they are limited with respect to one or another fundamental mechanism, expected results, environmental conditions etc. The complexity of the related challenges results from the fact that there is no single mechanism involved on one hand. On the other hand, despite available knowledge, the fundamental processes related to MIC corrosion still need to be clarified for every environmental condition and/or practical application. The topic of this work is linked to a broad research project on studying in detail the predominant mechanisms within MIC-related corrosion and corrosion control for low-carbon steel in marine environment. One of the main objectives of this research is to justify the potentially superior performance of an alternative impressed current cathodic protection (ICCP), based on pulse technology, in view of controlled microorganisms viability, hence efficient MIC control. With this respect, except steel electrochemical response in relevant conditions, the behaviour of microorganisms with regard response to cathodic polarization, in the course of bio-film formation and/or restricted bio-film growth, are of significant importance and need to be studied and clarified. To this end, the paper will discuss results from preliminary and on-going investigation, as follows: The global electrochemical response of steel in biotic and abiotic environment (simulated sea water), compared to response after pulse ICCP. In addition to recorded evolution of open circuit and on-potentials (within ICCP) with time, the results are in terms of polarization resistance and corrosion current density, respectively, derived from electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR), potentio-dynamic polarization (PDP) and cyclic voltammetry (CVA). The local electrochemical response, derived from scanning vibrating electrode technique (SVET) and scanning electrochemical microscope (SECM), adds-up to the global electrochemical behaviour of the tested steel. The results provide information for the distribution of ionic currents during bio-film formation or re-distribution (following ICCP), as well as alterations in oxygen availability due to microorganisms metabolism. Additionally, SVET and SECM provide in-situ information on altered ionic current flow after ICCP and/or subsequent changes in microorganisms viability. Finally, fluorescent microscopy supports the electrochemical tests and justifies the effect of cathodic polarization on microbial metabolism and restriction thereof, hence “visualises” the effect of the alternative ICCP as a MIC-control approach. The results from this work serve as a base for further investigation on the application of a hybrid, bio-based coating for control of excessive hydrogen evolution within ICCP. This is especially relevant for the practical situation, when bacterial metabolism reduces ICCP efficiency i.e. when bio-film formation in conditions of conventional ICCP increases the demand for enhancing cathodic polarization. It is expected that the bio-based coating, together with the alternative ICCP, will result in optimum protection with minimum overprotection for steel in marine environment. The concept of this novel solution will be also discussed.

Feature Extraction of Structures in Sea Water Using Self-Organizing Maps and Electromagnetic Waves

<pre><!--StartFragment-->The use of Self-Organizing Map (<span>SOM</span>) algorithm for feature extraction and dimensionality reduction applied to underwater object detection with Low Frequency Electromagnetic Waves is presented. Computer simulation is used to generate a direct model for the study region, and a Self Organizing Map Algorithm is used to fit the data and return a similar model, with smaller dimensionality and same characteristics. Results show that virtual sensors are created by the <span>SOM</span> algorithm with consistent predictions, filling the resolution gap of the input data. These results are useful for fastening decision making algorithms by reducing the number of inputs to a group of significant data.<!--EndFragment--></pre>

The entrainment of kaolinite particles in copper and gold flotation using fresh water and sea water

In this study, the recovery of kaolinite particles in copper and gold flotation using fresh water and sea water was investigated. Cryo-SEM analyses together with settling tests were employed to examine the formation of kaolinite network structures and its correlation with the entrainment of kaolinite particles. It was found that kaolinite had a negative effect on copper and gold grades of flotation concentrates in fresh water due to the aggregation of clay platelets in the pulp and the transport of clay aggregates into the froth. Sea water modified the association of kaolinite platelets with the formation of cross-linked network structures exacerbating the entrainment, and copper and gold grades. In addition to the compression of the double layer, the adsorption of cations on the clay platelets may also facilitate the formation of network structures in sea water.

Shallow water body data processing based on the seismic oceanography

Physical properties of sea water, such as salinity, temperature, density and acoustic velocity, could be demarcated through degradation of energy caused by water absorption, attenuation and other factors. To overcome the challenging difficulties in the quick monitoring of these physical properties, we have explored the high resolution marine seismic survey to instantly characterize them. Based on the unique wavefield propagating in the sea water, we have developed a new approach to suppress the noise caused by the shallow sea water disturbance and obtain useful information for estimating the sea water structure. This approach improves seismic data with high signal-to-noise ratio and resolution. The seismic reflection imaging can map the sea water structure acoustically. Combined with the knowledge of local water body structure profile over years, the instant model for predicting the sea water properties could be built using the seismic data acquired from the specially designed high precision marine seismic acquisition. This model can also be updated with instant observation and the complete data processing system. The present study has the potential value to many applications, such as 3D sea water monitoring, engineering evaluation, geological disaster assessment and environmental assessment.

Effect of Mg Content on the Performance of Al-Zn-Mg Sacrificial Anodes

Aluminum sacrificial anodes are widely used in cathodic protection of steel structures in sea water. In the present work, samples of Al-5.3 at.% Zn-x at.% Mg (x = 5.5-8.5) alloys were microstructurally and electrochemically characterized to evaluate their performance as Al-sacrificial anodes for cathodic protection of structures exposed to marine environments. The experiments focussed on the influence of Mg content on electrochemical behavior and efficiency. Mg was used in different concentrations ranging from 5.5 to 8.5 at.%. Short-term electrochemical tests, DNV RP B401, as well as polarization curves and electrochemical impedance spectroscopy were performed to obtain electrochemical behavior and efficiency and to reveal any tendencies to passivation. It is shown that by increasing Mg content an improvement of electrochemical properties of Al-alloy such as current capacity and then electrochemical efficiency can be obtained.

An Estimation Method of Vertical Sound Speed Profile in Mid-Deep Water Using Multipath Propagation

Oceanic current is closely related to such sea water structure as temperature distribution. To observe the change of current in mid-deep water, a method of estimating the vertical sound speed profile using multipath propagation is studied. In mid-deep water, sound is propagated by repeated reflection at both bottom and surface. We estimate the reflection loss of the sea bottom in Sagami Bay from the sound transmission experiment data. Then, using a mid-deep water model, we estimate the vertical sound speed profile from travel times of bottom and/or surface reflected rays. Good results show that estimation of the vertical sound speed profile is valid for mid-deep water monitoring.

Structure of sea water and its role in chemical mass transport between the sea and the atmosphere

Understanding interfacial phenomena associated with liquid water can be aided by a molecular model that envisions the pure bulk liquid as a mixture of flickering clusters and more or less monomeric water. Sea water solutes alter the local water structure into at least two structurally different types of hydration atmospheres, coulombic hydration surrounding ions and polar solutes and hydrophobic hydration enveloping nonpolar solutes and solute segments. The water structure (vicinal water) of the liquid boundary layer at the air-sea interface is theorized to resemble the hydrophobic hydration, and it may preferentially exclude ionic species and thereby give rise to the Na-K fractionation observed in nature.

ENGINEERING RESEARCH. COMMITTEE ON THE DETERIORATION OF STRUCTURES IN SEA-WATER . SUMMARY OF EXPERIMENTS CARRIED OUT BY THE COMMITTEE ON THE DETERIORATION OF STRUCTURES OF TIMBER, METAL, AND CONCRETE EXPOSED TO THE ACTION OF SEA-WATER. (INCLUDES TABLES).

Keywords COMMITTEE ON THE DETERIORATION OF STRUCTURES IN SEA-WATER, COMDETSTRSEAWAT PAINTS, ENGINEERING, RESEARCH, COMMITTEES, SEA, WATER, SEAWATER, DETERIORATION, STRUCTURES, EXPERIMENTS, TIMBER, METALS, CONCRETE, ACTION, EXPOSED, PRESERVATION, CORROSION, STEEL, IRON, REINFORCED, PROTECTION, PAINT... Show All

Deterioration of Structures in Sea Water

NOT the least important of the matters which concern the civil engineer engaged on port and maritime works, such as docks, jetties, wharves and piers, is the durability in a marine environment of the materials available for constructional purposes. Timber, iron and steel and concrete immersed in sea water are exposed to the action of agencies producing damage and

The Essential Qualities and the Application of Concrete to Timber Structures in Sea Water for the Purpose of Increasing Their Permanency

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