Artificial Seawater Conditions Research Articles

Investigation of Wear Properties and Corrosion Resistance of Electrodeposited Ni-P-PTFE Nanocomposite Coating on Mg-Li alloy

Ni-P-polytetrafluorethylene nanocomposite coatings based on Mg-Li alloy were successfully prepared by utilizing electrodeposition method. The nanocomposite coatings were investigated employing scanning electron microscopy, atomic force microscopy, and X-ray diffraction. The microstructure and composition of the coating were studied by friction, wear and corrosion tests. The experimental results reveal that when the concentration of PTFE is 3 g / L, deposition temperature is 70 °C, current density is 2 A/dm2, and pH of the plating solution is approximately 5.5, a uniform and dense Ni-P-PTFE nanocomposite coating is formed on Magnesium alloy substrate, and it exhibited a low coefficient of friction (∼1.5) and superior abrasion resistance. The co-deposition of PTFE particles can effectively reduce the friction coefficient and wear rate, and the wear mechanism is characteristic cutting wear. Under artificial seawater conditions, the experiments have demonstrated that the nanocomposite material possesses a corrosion current density of 3.9×10-5 A/cm2.

Crack growth in high strength mooring line steel under variable amplitude loading

Mooring lines are of key importance for the safe and reliable operation of numerous floating offshore structures. Due to the constantly changing wind and wave conditions acting on such structures, any fatigue crack growth in a mooring line will occur under cyclic loading of distinctly variable amplitude. This paper considers a long-term load history for mooring lines on a North Sea offshore platform. For fatigue testing purposes, a characteristic load sequence representing the actual load history in a condensed and simplified form is developed and presented. Fatigue crack growth rate test results for a grade R4 high strength mooring chain steel subjected to this variable amplitude load sequence is furthermore presented, including tests performed in air as well as under free corrosion conditions in artificial seawater. Based on comparison testing performed under variable- and constant amplitude conditions, the validity of a linear damage rule hypothesis for stable crack growth under the characteristic load sequence is investigated. This damage rule converts the load spectrum to an equivalent constant load range, making it a potentially useful tool for estimating fatigue crack growth in mooring chains when test data for a representative characteristic load sequence are unavailable. Results from the comparison testing are used to show that under stable fatigue crack growth conditions, while subjected to the characteristic load sequence developed for this offshore platform, the linear damage rule can be a reasonable assumption.

Influence of Sulfate-Reducing Bacteria on Corrosion Behavior of EQ70 High-Strength Steel

This work examines corrosion behavior of EQ70 high-strength steel under anaerobic conditions in artificial seawater containing sulfate-reducing bacteria (SRB). Polarization and electrochemical impedance spectra (EIS) tests were conducted. The results reveal that corrosion rate initially decreased at the beginning of immersion. However, as the immersion time progressed, the corrosion rate of the high-strength steel increased, attributed to SRB reproduction. The scanning electron microscopy (SEM) results demonstrate that the corrosion was more severe in artificial seawater containing SRB compared to that of seawater without SRB. The morphologies of confocal laser scanning microscopy (CLSM) demonstrate that, after 15 days of immersion, the average depth of the corrosion pits on the sample in the artificial seawater containing SRB was nearly double that of the sample in the SRB-free seawater.

RETRACTED: Temperature and pH endurable self-assembled camellia-like nanostructure achieved on zinc sheet with superamphiphobicity for fog harvesting

Easy-implement and low-cost fabrication of super-hydrophobic/super-oleophobic materials is vital for efficient fog harvesting. In this study, we introduce a simple two-step procedure based on Cu/1-octadecanethiol (ODT) self-assembled monolayer (SAM) modified zinc plates. Intriguingly, the process emulates the natural blooming of flowers: copper particle deposition and subsequent SAM formation lead to the progressive expansion of the surface, culminating in camellia-like nanostructures. The ensuing materials display water contact angle (WCA) and oil contact angle (OCA) of 160 ± 1° and 159 ± 1°, respectively. The formation of a layered petal structure that effectively traps air is recognized as the crucial factor in achieving superamphiphobicity. In addition to enhanced fog collection, the materials exhibit exceptional performance in acidic and basic environments (1 ≤ pH ≤ 14) as well as artificial seawater conditions. Furthermore, they demonstrate remarkable wear resistance and self-cleaning capabilities. The combination of these attributes ensures the robustness and stability necessary for efficient fog collection.

Mechanical Degradation and Failure Analysis of Different Glass/Basalt Hybrid Composite Configuration in Simulated Marine Condition.

This work aims to evaluate the failure mechanisms of plain glass and basalt fiber reinforced composites and a selected glass/basalt hybrid composite sequence subjected to artificial seawater conditions. Sets of plain and five hybrid composite configurations were fabricated by vacuum assisted resin injection technique (VARI), and subjected to seawater aged for 258 days at 30 °C and 70 °C followed by tensile, flexural and charpy impact testing, respectively. Failure analysis for dry and seawater-aged composites were undertaken using scanning electron microscopy (SEM). Results showed that some hybrid laminates with sandwich-like and alternating sequencing exhibited superior mechanical properties and ageing resistance than plain laminates. GB3 ([B2G2]S) type hybrid composite with basalt fiber outer plies retained 100% tensile strength and 86.6% flexural strength after ageing, which was the highest among all the laminates. However, GB4 ([BGBG]S) type specimen with alternating sequencing retained the highest residual impact strength after ageing. SEM analysis on the failed specimens showed fiber breaking, matrix cracking and debonding caused by fiber–matrix interface degradation due to seawater exposure. However different hybrid configurations to a considerable extent prevented crack propagation across specimens, hence altering the overall damage morphology among different specimens.

Evaluation of the Impact of Organic Fillers on Selected Properties of Organosilicon Polymer.

Eco-friendly composites are proposed to substitute commonly available polymers. Currently, wood–plastic composites and natural fiber-reinforced composites are gaining growing recognition in the industry, being mostly on the thermoplastic matrix. However, little data are available about the possibility of producing biocomposites on a silicone matrix. This study focused on assessing selected organic fillers’ impact (ground coffee waste (GCW), walnut shell (WS), brewers’ spent grains (BSG), pistachio shell (PS), and chestnut (CH)) on the physicochemical and mechanical properties of silicone-based materials. Density, hardness, rebound resilience, and static tensile strength of the obtained composites were tested, as well as the effect of accelerated aging under artificial seawater conditions. The results revealed changes in the material’s properties (minimal density changes, hardness variation, overall decreasing resilience, and decreased tensile strength properties). The aging test revealed certain bioactivities of the obtained composites. The degree of material degradation was assessed on the basis of the strength characteristics and visual observation. The investigation carried out indicated the impact of the filler’s type, chemical composition, and grain size on the obtained materials’ properties and shed light on the possibility of acquiring ecological silicone-based materials.

Transport analysis of particulate matter in media-saturated mesh tube filter for the desalination primary pretreatment process

Roughing filters (coarse media filtration) are a type of porous media filters used as pretreatment systems when the raw water contains a large amount of suspended particles and organic matter. Mesh tube filter media, roughing filter media composed of LDPE, are used in the process of removing suspended particles in wastewater treatment. In this study, we investigated the transport of suspended solids in saturated mesh tube filter media using kaolin particles (sizes range: 0.5–40 μm) and spherical SiO2 particles with particle sizes of 1.5, 10.4, and 19.5 μm. The results showed that the mesh tube filter media effectively removed suspended particles at sizes of 1–20 μm, and the removal rate of suspended particles under artificial seawater conditions was 5–50% higher than under freshwater conditions. It was also found that mechanism of removal of suspended particles varies with the velocity of the fluid by mass balance analysis. With high ion concentrations in the seawater conditions, the size of the suspended particles increased by 5–20%, which caused the suspended particles to be more strongly affected by gravity. The DLVO interaction energy analysis showed that the electrical attraction between suspended particles and filter media increased strongly in artificial seawater conditions.

Caesium adsorption on a zeolitic imidazolate framework (ZIF-8) functionalized by ferrocyanide

137Cs is one of the most hazardous radionuclides in nuclear waste owing to its toxicity. Developing an adsorbent for Cs+ with a high capacity and selectivity is a challenging task. A metal–organic framework (MOF) is a material with a high surface area that has been widely applied in wastewater treatment. Exploiting the affinity between ferrocyanide (FC) and Cs+, zeolitic imidazolate framework-8 (ZIF-8) was chemically functionalized with FC, ZIF-8-FC to selectively capture Cs+. After functionalization, ZIF-8-FC has a hollow morphology and small FC related crystals, which might result in better migration of Cs+ inside ZIF-8-FC. This synergistic effect was proven by the Qmax of ZIF-8-FC, 422.42 mg g−1, which is 15.9 times higher than that of ZIF-8. Additionally, ZIF-8-FC retained its good adsorption performance within a pH range of 3–11 and an excellent Cs+ selectivity even in artificial seawater conditions. The structure of ZIF-8-FC after adsorption proves its stability. Furthermore, the thermodynamic adsorption implied that higher temperatures are more favorable for Cs+ uptake. This work demonstrates the remarkable adsorption and selectivity of ZIF-8-FC, which make it a promising candidate for remediation of radioactive Cs+.

Characterization of Biofilm Formation and Coating Degradation By Electrochemical Impedance Spectroscopy

Recent findings showed severe localized corrosion of submerged steel bridge piles in a Florida bridge and was associated with microbial activity in presence of marine foulers (Permeh et al, 2017;2018). Microbiologically Influenced Corrosion (MIC) can cause severe degradation of civil infrastructure. MIC has often associated with the formation of biofilm (including the complex interaction of microbe communities and development of extracellular polymeric substances (EPS)) that can influence the corrosion process either by creating oxygen differential aeration cells or generating acidic substances and cathodic reactant depending on the type of bacteria. Sulfate reducing bacteria (SRB) has received much attention in the study of MIC of steel developed in natural waters (Melchers and Wells, 2006; Castaneda and Benetton, 2008). Reactions associated with SRB causes cathodic depolarization of steel leading to the reduction of sulfates to sulfides and promoting steel corrosion (Borenstein,1994). Coatings have been developed to mitigate MIC and marine fouling. Studies have shown that coating blistering and disbondment can occur as a result of microbial attack due to the production of metabolites that degrade coating chemical and physical properties (Mansfield et al.,1998; Muntasser et al.,2002). Recent work evaluated the corrosion mitigation properties of a commercially-available, water-based, self-polishing, antifouling coating in environments that supported SRB as part of a larger research program to identify susceptibility of steel degradation in natural waters due to MIC (Permeh et al.,2019). In the work described here electrochemical impedance spectroscopy (EIS) was conducted to identify microbial activity and degradation of an antifouling coating. EIS was conducted on steel coupons coated with an antifouling coating (with and without coating defects) exposed to SRB inoculated modified Postgate B solution. The exposed coating surface area was ~19.6 cm2 and the coating thickness was ~0.17-0.35 mm. A three-electrode configuration was used for EIS measurements where the coated steel plate was the working electrode, an activated titanium rod was used as a reference electrode, and an activated titanium mesh was used as a counter electrode. EIS measurements were made at OCP condition with 10 mV a.c. perturbation voltage and at frequencies 1Mhz>f>1Hz. The measurements resulted in impedance with multiple loops in the Nyquist diagram (as shown in Figure 1) associated with processes relating to the polymeric coating, development of surface layers (biofilm), and the steel interface. Fitting of the impedance response to equivalent circuit analogs were made to identify coating characteristics and surface layer formation during the experimental exposure in inoculated and non-inoculated solutions. The results revealed near-ideal capacitance for the polymeric coating and a decrease in coating pore resistance. In samples inoculated with SRB, a second high frequency loop developed indicating formation of surface films. The results from EIS indicated degradation of the coating due to its self-polishing characteristics and that formation of surface layers associated with SRB can form as biocide components of the coating become depleted. Continued SRB growth may allow development of marine fouling if the antifouling coating components become less effective and allow possible shelter for SRB to promote MIC. Further work to verify these characteristics in field settings are in progress. References Borenstein, S. (1994). Microbiologically influenced corrosion handbook. Elsevier.Castaneda, H., & Benetton, X. D. (2008). SRB-biofilm influence in active corrosion sites formed at the steel-electrolyte interface when exposed to artificial seawater conditions. Corrosion Science, 50(4), 1169-1183.Mansfield, F., Lee, C. C., Han, L. T., Zhang, G., & Little, B. (1998). The Impact of Microbiologically Influenced Corrosion on Protective Polymer Coatings. University of Southern California Los Angeles Dept of Materials Science And Engineering.Melchers, R. E., & Wells, T. (2006). Models for the anaerobic phases of marine immersion corrosion. Corrosion Science, 48(7), 1791-1811.Muntasser, Z., Al-Darbi, M., Tango, M., & Islam, M. R. (2002, January). Prevention of microbiologically influenced corrosion using coatings. In CORROSION 2002. NACE International. Permeh, S., Boan, M. E., Tansel, B., Lau, K., & Duncan, M. (2019, February). Update on Mitigation of MIC of Steel in a Marine Environment with Coatings. In Coatings+, SSPC 2019. Permeh, S., Li, B., Boan, M. E., Tansel, B., Lau, K., & Duncan, M. (2018, July). Microbially Influenced Steel Corrosion with Crevice Conditions in Natural Water. In CORROSION 2018. NACE International.Permeh, S., Reid, C., Echeverría Boan, M., Lau, K., Tansel, B., Duncan, M., & Lasa, I. (2017, April). Microbiological Influenced Corrosion (MIC) In Florida Marine Environment: A Case Study. In CORROSION 2017. NACE International. Figure 1

チタン合金の海水中における耐摩耗性に及ぼす摩擦改質の影響

This research focused on friction-based techniques for modifying the wear properties of a titanium alloy, particularly under seawater conditions. The surface modification processes employed were powder intrusion and friction stirring. Three different kinds of powder materials were used for the surface modification: Cr2N,TiN and Al2O3. Wear tests were conducted on the specimens under both dry and artificial seawater conditions. The results revealed that the Cr2N modified material presents excellent wear resistance under dry conditions, whereas modification using Al2O3 and Zn-coated Cr2N led to excellent wear properties under artificial seawater conditions.

Bioavailability of different chemical forms of dissolved silica can affect marine diatom growth

AbstractIn this study, we demonstrate that dissolved silica obtained from mineral (crystalline quartz), biogenic amorphous (diatomaceous earth) and artificial amorphous sources (Aerosil) influence the growth rate of two marine diatoms, Chaetoceros sp. and Skeletonema marinoi. Diatoms were reared in four different experimental conditions in artificial seawater containing either dissolved silica previously obtained through dissolution of the mineral crystalline quartz or two amorphous substrates, biogenic diatomaceous earth or artificial Aerosil silica. Sodium metasilicate was used as control. When the silica in the different media reached concentrations higher than 107 μm, particles were eliminated by filtration and the diatom cells were inoculated. Maximum cell density, growth and silica assimilation rates of both species in the presence of dissolved silica derived from crystalline quartz and metasilicate were higher than those obtained with the other silica sources. These results are discussed against the background of previous geochemical studies that have shown that silica–water interactions are strictly dependent on the silica polymorphs involved and on the ionic composition of the solution. Our results demonstrate that the soluble silicon compounds generated in seawater by crystalline sources are highly bioavailable compared with those generated by biogenic and amorphous materials. These findings are potentially of considerable ecological importance and may contribute to clarifying anomalous spatial and temporal distributions of siliceous organisms with respect to the presence of lithogenic or biogenic silica sources in marine environments.

Characterisation of calcareous deposits on freely corroding low carbon steel in artificial sea water

Calcareous deposits were formed on steel under cathodic protection conditions in artificial sea water at various potentials from −0·900 to −1·400 V(SCE). The deposition calcareous layers were characterised by electrochemical impedance spectroscopies, scanning electron microscopy observations and X-ray diffraction analyses. At 20°C, the deposits were composed of calcite CaCO3 when formed at various potentials in solution 1, of brucite Mg(OH)2 and aragonite CaCO3 when formed at potentials from −0·900 to −1·200 V(SCE) and only of brucite when formed at potentials E⩽−1·300 V(SCE) in solution 2. Magnesium seems to influence the corrosion behaviour of freely corroding steel by causing calcium carbonate to precipitate as aragonite. Aragonite is more effective in covering the surface than calcite and is therefore more functional in preventing oxygen from reaching the steel surface, thereby lowering the corrosion rate.

SRB-biofilm influence in active corrosion sites formed at the steel-electrolyte interface when exposed to artificial seawater conditions

Electrochemical evolution of the interface formed by carbon steel exposed to artificial seawater with nutrients in the presence and absence of mixed cultures that contain sulfate-reducing bacteria (SRB) is characterized by electrochemical impedance spectroscopy (EIS). The artificial seawater in sterile conditions progressively covered the surface of the steel sample with two different layers after 30 days of exposure. An outer layer is formed by a mixture of chlorides and phosphorus-based iron corrosion products with organic compounds from the culture media, and an inner layer is formed by corrosion products mixture constituted mainly by phosphorus-base products. Alternatively, under biotic conditions there was one heterogeneous layer composed by a mixture of phosphorous and sulfur-based corrosion products and biofilm. Three time constants were observed with EIS for sterile conditions. At low frequencies one constant is associated with the charge transfer resistance related to the iron dissolution reaction and inversely proportional to the active area; the porous resistance magnitudes at medium frequencies characterized the physicochemical properties of the inner layer, and high frequency described the electrical properties of the outer mixture layer. Low carbon steel in the presence of SRB (halophilic hydrogenotrophic) showed the impedance distribution after the formation of a corrosion product thick black layer mixed with organic composites and bio-entities. The SRB-biofilm enhanced the corrosion rate and influenced the appearance of diffusion controlled mechanism process. Electrical passive analogs in terms of constant phase elements characterized the evolution of the cover films formed and the impedance of the layers with time. The mechanisms are characterized based on the impedance response for three time constants in the absence of SRB and one time constant with a finite Warburg element when SRB are present in the electrolyte. The validation of the theoretical approximation with electrical analogs was in good agreement with the experimental results.

Succession of cellular states in a Salmonella typhimurium population during starvation in artificial seawater microcosms

The succession of the physiological states of Salmonella typhimurium cells under starvation-survival conditions in artificial seawater was investigated by flow cytometry and epifluorescence microscopy using direct examination of different cell functions. Measurements of substrate responsiveness (DVC method), real and potential respiration (redox dye 5-cyano-2,3-ditolyl tetrazolium chloride, CTC), membrane permeability (BacLight™ kit), as well as DNA content (Hoechst 33342 staining) reveal an important heterogeneity within the population, and suggest a progressive physiological cell alteration throughout the starvation process. The transition steps between culturable and prelytic cells are described.

Characterization of calcareous deposits in artificial seawater by impedance techniques: 3—Deposit of CaCO 3 in the presence of Mg(II)

Calcareous deposits were formed on steel under cathodic protection conditions in artificial seawater at various potentials from −0.9 to −1.4 V/SCE. The deposition kinetics was analysed by chronoamperometry measurements and the calcareous layers were characterized by electrochemical and electrohydrodynamical impedance spectroscopies, scanning electron microscopy observations and X-ray diffraction analyses. At 20 °C, the deposits were composed of aragonite CaCO 3 when formed at potentials E comprised between −0.9 and −1.1 V/SCE, of brucite Mg(OH) 2 and aragonite when formed at −1.2 V/SCE, and only of brucite when formed at potentials E≤−1.3 V/SCE. However, the in situ impedance techniques demonstrated the presence of a Mg(II)-containing porous layer along with the aragonite deposit at E≥−1.1 V/SCE. In seawater enriched with Mg 2+, the deposition of aragonite was almost totally inhibited, and the behavior of the film containing Mg(II) could be described.

Examinations on the morphology of tarnish layers grown on stainless 18-10 chromium nickel steels

18-10 chromium nickel steels are generally valid as well weldable. However, during thermal joining oxides are formed in the heat affected zone, whose structure and composition essentially differs from the morphology of passive layers. The steel qualities X6 CrNiTi 18-10 (materials no. 1.4541) and X5 CrNiMoTi 17-12-2 (materials no. 1.4571) were examined on their tarnish growing behaviour by means of XPS/sputtering, transmission electron microscopy and atomic force microscopy. Information on the pitting corrosion resistance of annealed metal sheets was received by ageing them in iron chloride solution and by measuring the current density-potential curves under quasi-stationary conditions in artificial sea water.

Succession of cellular states in a Salmonella typhimurium population during starvation in artificial seawater microcosms

The succession of the physiological states of Salmonella typhimurium cells under starvation-survival conditions in artificial seawater was investigated by flow cytometry and epifluorescence microscopy using direct examination of different cell functions. Measurements of substrate responsiveness (DVC method), real and potential respiration (redox dye 5-cyano-2,3-ditolyl tetrazolium chloride, CTC), membrane permeability ( BacLight™ kit), as well as DNA content (Hoechst 33342 staining) reveal an important heterogeneity within the population, and suggest a progressive physiological cell alteration throughout the starvation process. The transition steps between culturable and prelytic cells are described.

2 Molecular Mechanisms of Gamete Recognition in Sea Urchin Fertilization

Publisher Summary This chapter discusses the understanding of the molecular mechanisms involved in the echelon of species-specific recognition steps among sea urchin gametes. This chapter describes the implications of this novel class of cell recognition molecules for the overall fertilization process. Early studies on sea urchin fertilization, implicated a high molecular-weight glycoconjugate as an egg receptor for sperm. Characterization of a partially purified receptor preparation showed that the receptor bound to sperm and inhibited fertilization in a species-specific manner. The primary structure and the subunit composition of the biologically active sperm receptor exists only for the receptor from Strongylocentrotus purpurarus , a sea urchin species, present on the west coast of North America is discussed in this chapter. Sea urchins are common marine organisms that can be held in captivity under simple conditions and produce gametes for the periods ranging from weeks to many months, depending on the species. For these reasons, the sea urchin is the most highly studied model system for research on fertilization. Mature gametes can be obtained in large quantities and eggs can be fertilized in vitro under well-defined conditions in artificial sea water.

Isolation of aVibrio choleraetransposon-mutant with an altered viable but nonculturable response

We have isolated more than 2500 mutants of Vibrio cholerae by using transposon mutagenesis. Mutants were screened under low nutrient conditions in artificial seawater for an altered viable but nonculturable response, compared to the wild-type. Mutant JR09H1 entered the viable but nonculturable state more rapidly than the wild-type at both 25 degrees C and 4 degrees C.

A carbon-13 method for evaluating degradation of starch-based polymers

A new method for evaluating biodegradability of starch-based and certain other polymer blends uses the pre- and postexposure stable carbon isotope composition of material coupled with weight loss data to determine which components have degraded. The naturally occurring stable isotope of carbon.13C, is enriched in corn starch (δ13C, approx. −11‰) compared to petroleum-derived synthetic polymers (δ13C, approx. −32‰). Results on starch-synthetic polymer blends indicate that the δ13C signatures of these blends are near-linear mixtures of their component δ13C. Values of a δ13C for starch-synthetic polymer blends exposed to biologically active laboratory soil and artificial seawater conditions are depleted in13C compared to unexposed samples, suggesting loss of the starch component. Combined with weight loss data for the exposed samples, the δ13C values are statistically consistent with models requiring loss of the soluble component glycerin, followed by loss of starch, then petrochemical polymer, or simultaneous loss of starch and petrochemical polymer. Replicate δ13C analyses of starch-synthetic polymer blends increase the statistical power of this relatively inexpensive, accessible technique to discriminate between degrading components.