Immersion In Natural Seawater Research Articles

Fouling-Resistant Behavior of Hydrophobic Surfaces Based on Poly(dimethylsiloxane) Modified by Green rGO@ZnO Nanocomposites.

In line with global goals to solve marine biofouling challenges, this study proposes an approach to developing a green synthesis inspired by natural resources for fouling-resistant behavior. A hybrid antifouling/foul release (HAF) coating based on poly(dimethylsiloxane) containing a green synthesized nanocomposite was developed as an environmentally friendly strategy. The nanocomposites based on graphene oxide (GO) and using marine sources, leaves, and stems of mangroves (Avicennia marina), brown algae (Polycladia myrica), and zinc oxide were compared. The effectiveness of this strategy was checked first in the laboratory and then in natural seawater. The performance stability of the coatings after immersion in natural seawater was also evaluated. With the lowest antifouling (17.95 ± 0.7%) and the highest defouling (51.2 ± 0.9%), the best fouling-resistant performance was for the coatings containing graphene oxide reduced with A. marina stem/zinc oxide (PrGZS) and graphene oxide reduced with A. marina leaves/zinc oxide with 50% multiwall carbon nanotubes (PrGZHC50), respectively. Therefore, the HAF coatings can be considered as developed and eco-friendly HAF coatings for the maritime industry.

Durability Study of Glass/Carbon Hybrid Composites Immersed in Seawater for Marine Application

The hybridization of carbon fiber (CFRP) and glass fiber (GFRP) composites is required to overcome the disadvantages of GFRP composites and their commercial feasibility for marine applications. This study was conducted on a hybrid glass/carbon composite with a vinyl ester matrix made by vacuum-assisted resin infusion process with a stacking sequence of [GCG2CG2C] s. Composites are immersed in natural seawater for up to 6 months. The maximum weight gain of e-glass/carbon hybrid composite is 0.79%. The results showed that the tensile, shear and compressive strengths of the glass/carbon hybrid composite after immersion in natural seawater decreased to 19%, 13%, and 50%, respectively. The decrease in compressive strength is the highest compared to others. It indicates that compressive strength should be of more significant concern for marine environmental applications. SEM analysis exhibited that seawater absorption causes the matrix, fiber, and fiber/matrix interface degradation. It is indicated by the absence of a firm matrix fracture surface, the number of fractures in the thread, the presence of fiber/matrix debonding, and fiber pull-out in the specimen after immersion in seawater. It is the cause of the decrease in the mechanical properties of the hybrid composite.

Corrosion behavior of the high‐strength low alloy steel welded joint in natural seawater

AbstractIn this work, the corrosion behavior of high‐strength low alloy (HSLA) steel welded joints in natural seawater solution was investigated by electrochemical and immersion tests. The experimental results prove that the corrosion resistance of the weld metal (WM) was higher than that of the base metal (BM). The scanning Kelvin probe results show that the potential distribution of the BM zone is lower than the heat‐affected zone (HAZ) and WM zone. The scanning vibrating electrode technique results demonstrate that the initial attack for the HSLA welded joint majorly took place in the BM zone after immersion in natural seawater. The corrosion morphology of the HSLA welded joint after immersion was observed by scanning electron microscope. The corrosion morphology of BM and HAZ regions tends to be uniform corrosion, whereas it is mainly pitting corrosion for the WM zone.

Anti-biofouling bio-adsorbent with ultrahigh uranium extraction capacity: One uranium resource recycling solution

Uranium extraction from seawater is an effective solution to the shortage of uranium resources on land. However, because of the high salinity in seawater, an extremely low uranium concentration (~3.3 ppb) and biofouling caused drastically decrease the performance of adsorbents, and the practical development of uranium extraction from seawater still faces major challenges. Here, we demonstrated a simple strategy to utilize waste feather fiber (FF) to prepare anti-biofouling amidoxime functionalized FF (FF-Cu2O/AO), which was applied to the extraction uranium from seawater. The introduction of Cu2O endows FF-Cu2O/AO with anti-biofouling and enhances the binding of uranyl ions to amidoxime. FF-Cu2O/AO exhibited outstanding uranium adsorption performance, adsorbing 816 mg-U/g-Ads from 8 ppm uranium-spiked water. Following immersion in natural seawater for 30 days, the uranium extraction capacity of FF-Cu2O/AO reached 7.73 mg-U/g-Ads. More importantly, the strategy can be used for the preparation of other uranium adsorbents based on amidoxime functionalized polymer fibers to provide antibacterial and improved adsorption performance. Economic analysis shows that the cost of FF-Cu2O/AO adsorption of uranium from natural seawater is much lower than that of conventional adsorbents. Therefore, FF-Cu2O/AO would be an outstanding candidate for extracting uranium from seawater because of its high uranium extraction capacity, anti-biofouling and low-cost.

The study of long-term durability and bio-colonization of concrete in marine environment

The purpose of this paper is to study the long-term durability and bio-colonization of concrete in marine environment. In this work, concrete formulations were developed and optimised by varying the type of cement (CEMII and CEMV) and introducing shellfish by-products (Oyster Shells) into their composition (by substituting 20% by weight of 4/10 aggregates). Four concrete formulations were thus studied. The durability of these materials upon bio-colonization were tested after 90 days, 180 and 360 days of immersion in natural seawater. The monitoring of the photosynthetic activity of biofilms and the biomass on the materials surface showed a better acclimatisation of the microphytobenthos in CEMII 20% Shells concrete than in other concretes despite a lower colonization on this concrete. It was also noticed that the chlorophyll biomass was the highest in concrete CEMV 20% Shells after 360 days. During immersion, the mechanical strengths of CEMII 0% Shells, CEMII 20% Shells and CEMV 20% Shells increased. At long term of immersion, the chloride ions diffusion was more reduced, in natural seawater, for CEMII 0% Shells, CEMII 20% Shells and CEMV 20% Shells concretes than for concrete CEMV 0% Shells. these results lead to the assumption that the accumulation of biofilm plays a role as protective barrier against the action of chloride ions. Finally, it appears that the concrete CEMII 20% Shells is the most suitable concrete mix design for marine infrastructure amongst the tested designs.

L-Arginine-Incorporated Cement Mortar as Sustainable Artificial Reefs

L-arginine is one of the amino acids found in plant seeds. In the present study, various amounts (i.e., 3%, 5%, 10%) of L-arginine were added to cement mortar to investigate the compressive strength, workability, leaching behavior, and pH change in distilled and natural seawater, as well as dissolved nitrogen and growth of chlorophyll-a (Chl-a) by immersion in natural seawater. The compressive strength of the cement mortar is decreased with increase in L-arginine content owing to the high flow/slump and air content. A concentration of 10% L-arginine significantly promoted the growth of Chl-a on the cement mortar for up to 56 days of immersion in natural seawater. This is due to the availability of high dissolved nitrogen and pH inside the pores. This study recommends the use of L-arginine in artificial reef structures where marine ecosystems can be maintained.

An Ion-Crosslinked Supramolecular Hydrogel for Ultrahigh and Fast Uranium Recovery from Seawater.

Large-scale uranium extraction from seawater is a crucial but challenging part of nuclear power generation. In this study, a new ion-crosslinked supramolecular Zn2+ -poly(amidoxime) (PAO) hydrogel that can super-efficiently adsorb uranium from seawater is explored. By simply mixing two solutions of zinc chloride and PAO, a supramolecular Zn2+ -PAO hydrogel is achieved via the interaction between zinc cations and amidoxime anions. In contrast with existing amidoxime-functionalized hydrogel-based adsorbents having low PAO contents and fiber-based adsorbents with weak hydrophilicity, the PAOs can be directly crosslinked using a small quantity of superhydrophilic zinc ion. Thus, a supramolecular hydrogel is formed, having both a high content of well-dispersed PAOs and good hydrophilicity. Relative to reported adsorbents, this low-cost hydrogel membrane exhibits outstanding uranium adsorption performance, reaching 1188 mg g-1 of MU /Mdry gel in 32 ppm uranium-spiked water. More importantly, after immersion in natural seawater for only 4 weeks, the uranium extraction capacity of the Zn2+ -PAO hydrogel membrane reaches 9.23 mg g-1 of MU /Mdry gel . This work can provide a general strategy for designing a new type of supramolecular hydrogel, crosslinked by various bivalent/multivalent cation-crosslinkers and even many other superhydrophilic supramolecular crosslinkers, for the high-efficient and massive extraction of uranium from seawater.

Self‐Stratifying Silicone Coating with Nonleaching Antifoulant for Marine Anti‐Biofouling

AbstractChemical immobilization of antifoulant groups to polymers is a promising approach to develop ecofriendly antifouling materials with static antifouling ability and a durable efficacy. In this work, telomer of dodecafluoroheptyl methacrylate (DFMA), triclosan acrylate (TA), and 3‐mercaptopropyl trimethoxysilane (KH590) is grafted to bis‐silanol terminated poly(dimethylsiloxane) (PDMS), yielding a novel self‐stratifying silicone coating containing nonleaching antifoulants. X‐ray photoelectron spectroscopy (XPS) analysis reveals that the antifoulant groups are enriched on the coating surface due to DFMA migration. Such a modified PDMS coating can significantly inhibit the growth of marine bacterial biofilm and the adhesion of diatoms owing to the nonleaching antifoulant groups. On the other hand, the coating exhibits a good fouling release performance since it inherits the low surface energy (≈20 mJ m−2) and low elastic modulus (<2 MPa) from PDMS forming a physically dynamic surface. Marine field tests demonstrate that the coating has excellent antifouling ability after immersion in natural seawater for more than 6 months.

A Review on Deterioration of Mechanical Behaviour of High Strength Materials under Corrosive Environment

Surface corrosion has a major influence on ageing of high strength materials that leads to degradation in mechanical properties. Therefore,design of a component frequently implores the engineer to minimize the possibility of failure particularly by environmental deterioration. Effect of corrosive environment on high strength materials of Aluminum alloys and steels is studied. The influence of corrosion on material loss and deprivation of mechanical behaviour such as ultimate strength, yield strength and fatigue resistance arereviewed and presented.Salt spray test as per ASTM B117 and immersion in natural sea water are the usual practices followed to induce corrosion. It is evident from the literatures that corrosion has a significant effect on deterioration of mechanical behaviour of the materials.

Synergistic effects of different co-monomers on the uranium adsorption performance of amidoximated polyethylene nonwoven fabric in natural seawater

Several co-monomers were co-grafted with acrylonitrile onto polyethylene nonwoven fabric to prepare amidoximated sorbents. The grafted co-monomer was found to play an important role in the uranium adsorption capacity and sorption selectivity of amidoximated sorbent in natural seawater in the following order: acrylamide (AAm) < acrylic acid (AA) < itaconic acid (ITA) < methacrylic acid (MAA), which agreed well with the result in U-spike brine. The amidoximated sorbent co-grafted with MAA exhibited the highest uranium adsorption capacity (1.05 mg/g) and the best uranium/vanadium sorption selectivity (U/V mass ratio: ~ 0.95) after 56 days of immersion in natural seawater.

Localized corrosion of carbon steel in marine media: Galvanic coupling and heterogeneity of the corrosion product layer

Corrosion product layers formed on carbon steel coupons after 6–8 years of permanent immersion in natural seawater were characterized by X-ray diffraction and μ-Raman spectroscopy. Some of the coupons showed blisters of corrosion products on a surface covered elsewhere by a much thinner layer. In anodic zones, the formation of the sulfate green rust proved to be favored at the expense of that of magnetite. In contrast, the formation of magnetite was favored in cathodic zones, together with that of aragonite and carbonated corrosion products. The galvanic effects are then self-sustaining via their influence on the corrosion products.

Long term immersion in natural seawater of Flax/PLA biocomposite

Innovation in sailing yacht design must include current environmental concerns such as resource depletion and waste management. Indeed most of the materials used today are petro-based and cannot offer viable end of life treatment. Fully biodegradable natural fibre reinforced biopolymers are being increasingly studied as they offer high specific stiffness and low environmental footprint. However, their ageing mechanisms are still not well understood.The present article gives information on 2 years natural seawater aging effect on injection-molded Flax/PLA biocomposite. Biocomposites suffer from relatively high moisture absorption which is controlled by the vegetal fibres. Simple rules of mixtures allow the determination of weight gain for flax fibres which is around 12%. Bundles of fibres and especially middle lamellae influence water uptake. Water alters flax fibres and their biocomposites, since their mechanical properties (Young’s modulus and tensile strength) are reduced with aging. A linear relationship is observed between water uptake and loss of mechanical properties. Load–unload cycles highlight damage occuring earlier than unaged biocomposites. This damage can be induced by fibre degradation and washing out of soluble components especially the fibre bundles cement, and by debonding of fibre bundles linked to their swelling.

Waterborne signaling primes the expression of elicitor-induced genes and buffers the oxidative responses in the brown alga Laminaria digitata.

As marine sessile organisms, seaweeds must respond efficiently to biotic and abiotic challenges in their natural environment to reduce the fitness consequences of wounds and oxidative stress. This study explores the early steps of the defense responses of a large marine brown alga (the tangle kelp Laminaria digitata) and investigates its ability to transmit a warning message to neighboring conspecifics. We compared the early responses to elicitation with oligoguluronates in laboratory-grown and harvested wild individuals of L. digitata. We followed the release of H2O2 and the concomitant production of volatile organic compounds. We also monitored the kinetics of expression of defense-related genes following the oxidative burst. Laboratory-grown algae were transplanted in kelp habitats to further evaluate their responses to elicitation after a transient immersion in natural seawater. In addition, a novel conditioning procedure was established to mimic field conditions in the laboratory. Our experiments showed that L. digitata integrates waterborne cues present in the kelp bed and/or released from elicited neighboring plants. Indeed, the exposure to elicited conspecifics changes the patterns of oxidative burst and volatile emissions and potentiates this kelp for faster induction of genes specifically regulated in response to oligoguluronates. Thus, waterborne signals shape the elicitor-induced responses of kelps through a yet unknown mechanism reminiscent of priming in land plants.

Electrochemical anticorrosion behaviors of the electroless deposited Ni–P and Ni–P–PTFE coatings in sterilized and unsterilized seawater

The Ni–P and Ni–P–PTFE coatings were deposited on mild carbon steel surface via electroless deposition process. The as-deposited coatings were characterized through XRD, SEM, and EDS. The electrochemical anticorrosion behaviors of the coatings in natural seawater were investigated by measurements of potentiodynamic polarization curves, open circuit potential, and electrochemical impedance spectra. The results showed that by immersion in natural seawater for 3–7 days the Ni–P and Ni–P–PTFE coatings could provide maximum protection for the substrate. With regard to the PTFE incorporation, the coating with large amount of PTFE possessed a porous microstructure and hence poor electrochemical anticorrosion performance. Concerning the effect of the ocean microorganisms noticeable variations on electrochemical parameters have been observed though reliable consequence was yet to draw via cultivation and breeding of the ocean microorganisms in subsequent work.

Crevice Corrosion of Alloy 625 in Natural Seawater

Abstract An experimental study was conducted to determine the influence of temperature on crevice corrosion initiation for Alloy 625 (UNS N06625) in natural seawater. These tests showed that there was a critical potential-temperature-time relationship needed to initiate crevice corrosion. The potential necessary to cause crevice corrosion on Alloy 625 decreased (became less noble) when the temperature was increased from ambient to 40°C. The crevice initiation potential decreased from 300 mV for ambient temperature seawater to 100 mV for 40°C seawater. Crevice initiation potentials were essentially unchanged between 40°C and 65°C, while the time required to initiate crevice corrosion decreased as temperature increased. In a second aspect of this work, natural seawater exposure studies were conducted to determine if there is a mechanistic connection between ennoblement (the gradual elevation of corrosion potential that occurs during long-term continuous immersion in natural seawater) and crevice corrosion i...

Kinetics of conditioning layer formation on stainless steel immersed in seawater

Adhesion of microorganisms to surfaces in marine environments leads to biofouling. The deleterious effects of biofilm growth in the marine environment are numerous and include energy losses due to increased fluid frictional resistance or to increased heat transfer resistance, the risk of corrosion induced by microorganisms, loss of optical properties, and quality control and safety problems. Antifouling agents are generally used to protect surfaces from such a biofilm. These agents are toxic and can be persistent, causing harmful environmental and ecological effects. Moreover, the use of biocides and regular cleaning considerably increase the maintenance costs of marine industries. An improved knowledge of bio‐film adhesion mechanisms is needed for the development of an alternative approach to the currently used antifouling agents. The aim of this study is to characterise the chemical composition of the molecules first interacting with stainless steel during the period immediately following immersion in natural seawater and to elucidate the kinetics of the adsorbtion process. Proteins are shown to adhere very rapidly, closely followed by carbohydrates. The distribution on the surface of organic molecules is also examined. The ad‐sorbate on the surface is not a continuous film but a heterogeneous deposit, whose average thickness varies widely. The cleaning procedures used affect the adsorption kinetics. In particular, cleaning with hexane results in slower adsorption of nitrogen‐containing species than does cleaning in acetone.

Evidence for the formation of organic films on metal surfaces in seawater

The adsorption of substances from seawater onto metal surfaces was investigated using a combination of techniques which included scanning electron microscopy, ellipsometry, surface potential measurements, Auger and ESCA spectroscopy, and contact angle determinations. The data were consistent with the formation of an organic film on the metal surfaces following immersion in natural seawater. No such films were observed on surfaces exposed to artificial seawater. Scanning electron micrographs indicated that living organisms were not present in the adsorbed material. The thickness of the film increased over a period of hours as deduced by ellipsometric measurements. The data from the experiments where the Auger technique was applied showed presence of oxide layers in addition to the organic material.

Assessment of corrosion rate of steel in sea water by polarization resistance technique

Linear polarization techniques have been applied to a corrosion system, plain carbon and low-alloy steels in sea water, featured by time-dependent phenomena. Polarization resistance measurements have been interpreted according to equivalent circuits representative of the steel surface behaviour in sea water, in order to avoid misleading contributions arising from the presence of solid corrosion products. Electrochemical data are in good agreement with weight loss measurements throughout four years of immersion in natural sea water and give information about the corrosion mechanisms, mainly based on the settling of localized macro-cathodic and anodic areas.