Simulated Deep Sea Research Articles

Modeling the corrosion behavior of Ni-Cr-Mo-V high strength steel in the simulated deep sea environments using design of experiment and artificial neural network

Corrosion in complex coupling environments is an important issue in corrosion field, because it is difficult to take into account a large number of environment factors and their interactions. Design of Experiment (DOE) can present a methodology to deal with this difficulty, although DOE is not commonly spread in corrosion field. Thus, modeling corrosion of Ni-Cr-Mo-V steel in deep sea environment was performed in order to provide example demonstrating the advantage of DOE. In addition, an artificial neural network mapping using back-propagation method was developed for Ni-Cr-Mo-V steel such that the ANN model can be used to predict polarization curves under different complex sea environments without experimentation. Furthermore, roles of environment factors on corrosion of Ni-Cr-Mo-V steel in deep sea environment were discussed.

Influence of a simulated deep sea condition on the cathodic protection and electric field of an underwater vehicle

To investigate the effect of the deep sea condition on the corrosion behavior, cathodic protection and electric field of underwater vehicles, potentiodynamic polarization tests were carried out under a simulated deep sea condition. A 3-D boundary element method (BEM) was used for an underwater vehicle with and without sacrificial anode cathodic protection (SACP). The simulated deep sea condition influenced the cathodic polarization curves due to the difference between the cathodic reactions. Under the deep sea condition, the cathodic protection potential criterion was more easily satisfied as the protection current density of SACP was decreased. The electric field underneath the underwater vehicle showed that the deep sea condition decreased the electric field due to the lower current density and the shape of the electric field distribution changed from one dipole to two dipoles.

Degradation Behavior of a Modified Epoxy Coating in Simulated Deep-sea Environment

Degradation Behavior of a Modified Epoxy Coating in Simulated Deep-sea Environment

Corrosion Behaviors of 10CrNiCu High Strength Steel in Simulated Deep Sea Environment of High Hydrostatic Pressure and Low Dissolved Oxygen

Abstract This paper investigated 10CrNiCu high strength steel in a simulated deep sea environment of high hydrostatic pressure (HP) and low dissolved oxygen (DO) using microstructures, rust compositions, and electrochemical measurements. The results show that primary form of steel corrosion in this simulated high HP and low DO environment is pitting. Using cyclic voltammetry (CV) and laser Raman spectrum, it is found that HP and DO all accelerate corrosion rates, but they affect corrosion processes in different ways. HP simultaneously accelerates anodic and cathodic reaction rates, whereas DO mainly accelerate cathodic reaction rates. In the environment of high HP and low DO, oxygen concentration cell corrosion has a tendency to form on steel surface, which can accelerate pitting.

Effect of dissolved oxygen and coupled resistance on the galvanic corrosion of Cr‐Ni low‐alloy steel/90‐10 cupronickel under simulated deep sea condition

The influence of dissolved oxygen content (DOC) and coupled resistance on the galvanic corrosion rate of Cr‐Ni low‐alloy steel (FeCrNi) coupled with 90Cu‐10Ni cupronickel alloy in simulated 500 m deep sea environment was investigated by means of weight loss measurements and scanning electron microscopy. The results indicated that the galvanic corrosion rate increased with the increase of DOC and decreased with the resistance increased. FeCrNi showed pitting corrosion in low DOC condition and uniform corrosion in high DOC sea water. Moreover, the galvanic corrosion rate at 50 at was bigger than that of 1 at. Galvanic corrosion rate was reduced 99% by increasing the resistance from 0 to 2000 Ω between FeCrNi and CuNi. The results of this research can be used to guide ocean engineering facilities design and galvanic corrosion control.

Comparative study on the stress corrosion cracking of X70 pipeline steel in simulated shallow and deep sea environments

The stress corrosion cracking (SCC) behavior of X70 steel in simulated shallow and deep sea environments was studied using potentiodynamic polarization measurement, a slow strain rate tensile (SSRT) test and scanning electron microscopy (SEM). The results indicate that the predominant cathodic reaction changes from an oxygen reduction reaction to the hydrogen evolution reaction as the dissolved oxygen (DO) content decreases. In the simulated deep sea environment, the SCC susceptibility of X70 steel decreased first, reached its lowest point at 15MPa and then increased as the simulated sea hydrostatic pressure (HP) further increased. This is consistent with the regularity for the change of the cathodic hydrogen evolution reaction current density iH at Ecorr, which indicates that the HP may influence the SCC susceptibility of X70 steel by changing the permeated hydrogen concentration.

The effect of hydrogen on stress corrosion behavior of X65 steel welded joint in simulated deep sea environment

In order to investigate stress corrosion cracking (SCC) of X65 pipeline steel and its welded joint area in deep sea environment. The simulated methods were used to obtain the welded joint of hardening and softening tissue in heat affected zone (HAZ) by annealing at 1300°C for 10min and then, normalized in air and quenched in water respectively; the other was to get 1000m depths of marine environment. The effect of hydrogen on SCC behavior of X65 pipeline steel in simulated deep sea environment was analyzed by a combination of hydrogen-charging, slow stain rate test (SSRT), scanning electron microscope (SEM) and electrochemistry. Results demonstrated that with the increasing of charging current density, Fracture of as-received appeared brittle characteristics and normalized and quenched steel generated micro cracks, Hydrogen-charging will enhance the SCC susceptibility of the steel in simulated deep sea environment. The corrosion potential of X65 steels was low in deep sea environment with hydrogen evolution reaction and showed some SCC sensitivity in deep sea environment. Heat treatment altered the microstructure of the steel, resulting in a change of SCC susceptibility. In particular, the quenched steel with a bainite micro-structure which had a higher SCC susceptibility than as-received and normalized steel in deep sea environment.

Galvanic Corrosion of 70-30 Copper-Nickel Alloy in Contact with Nickel-Aluminum Bronze in Simulated Deep Sea Environment

The galvanic corrosion behavior of 70-30 copper-nickel alloy as a brand new seawater pipe material and nickel-aluminum bronze as the commonly used pipe valve material in simulated low temperature conditions of deep sea was studied. The galvanic corrosion potential and galvanic current density of the pair were monitored, and the galvanic corrosion tendency and effect at different temperature were evaluated. Combined with the electrochemical measurements, the influence of seawater temperature on galvanic corrosion behavior was also discussed. The results showed that as the result of coupling, 70-30 copper-nickel alloy acting as the coupled cathode was prevented from corrosion, while nickel-aluminum bronze became the sacrificial anode. With the decrease of seawater temperature, the galvanic corrosion tendency and galvanic corrosion rate of the pair decreased. The change in galvanic corrosion tendency with seawater temperature was attributed to the different electrochemical properties induced by the inherent difference in chemical compositions of the alloys. The low galvanic corrosion rate and effect were related to the reduced mass transfer rates at low temperature. Moreover, the electrochemical behavior of the copper alloys was much sensitive to the change in the amount of dissolved oxygen at the lower seawater temperature, especially for the alloy with higher passivation ability, i.e., 70-30 copper-nickel alloy.

Effect of cross linking degree and adhesion force on the anti-corrosion performance of epoxy coatings under simulated deep sea environment

Deep sea exploitation represents the future direction for its abundant resources, while organic coatings can play a very important role in ocean engineering for corrosion protection. In this paper, under simulated deep sea environment in the laboratory, the effect of the crosslink density and the adhesion force of the coatings on the anti-corrosion performance of two different types of epoxy coatings was studied by using electrochemical impedance spectroscopy (EIS) and adhesion test. The results showed that the deterioration of coatings’ property of corrosion protection under simulated deep sea environment was much faster than that of under normal pressured seawater. However, the diffusion velocity of water molecule through epoxy coatings decreased with increasing of the crosslink density and the adhesion force of the coatings. Therefore, the capability of corrosion protection could be improved by increasing the density of crosslink of the coatings within some extent and by increasing the adhesion force of the coatings.

Electrochemical Behaviors of Organic Coating/Matal Substrate under Simulated Deep Sea Environment PartⅠ.Effects of Seawater Pressure on Transportation Behavior of Water Through Coating and Coating′s Protective Performance

Electrochemical Behaviors of Organic Coating/Matal Substrate under Simulated Deep Sea Environment PartⅠ.Effects of Seawater Pressure on Transportation Behavior of Water Through Coating and Coating′s Protective Performance

Biodegradation of Synthetic Base Fluid Surrogates in Gulf of Mexico Sediments under Simulated Deep-Sea Conditions

In this study, an anaerobic marine biodegradability test was adapted to study the fate of synthetic base fluid (SBF) surrogates, ethyl oleate and tetradecene, by deep-sea microorganisms. Sediment samples from hundreds of meters deep in the Gulf of Mexico were incubated at low temperatures (4 degrees C) and high hydrostatic pressure in steel vessels. Stimulation of indigenous microbial communities to SBF biodegradation was evident in the fact that the rate of removal of ethyl oleate was greater in sediments that had some previous exposure to SBF (first-order decay coefficient kof -0.22 +/- 0.02 week(-1)) compared to unexposed control sediments (first-order decay coefficient k of -0.11 +/- 0.02 week(-1)). When sulfate-linked tetradecene degradation occurred within the test period, the activity could also be modeled as a first-order decay following an initial lag phase, with an average decay coefficient of k = -0.05 +/- 0.01 week(-1). This study also revealed that the degradation of SBF surrogates by microorganisms collected from deep-sea sediments was not significantly effected by the hydrostatic incubation pressure.

Monitoring the Impact of Simulated Deep-sea Mining in Central Indian Basin

Monitoring of deep-sea disturbances, naturai or man-made, has gained significance due to the associated sediment transport and for the ensuing alterations in environmental conditions. During the Indian Deep-sea Environment Experiment (INDEX), resuspension of deep-sea sediment in the Central Indian Basin (CIB) resulted in an increase and lateral movement of suspended particles, vertical mixing of sediments, changes in sedimentological, biochemical, and geochemical conditions and an overall reduction in benthic biomass. Monitoring the conditions 44 months after the experiment has shown a partial recovery of the benthic ecosystem, with indications of restoration and recolonization.

2348 メタンハイドレイトの生成・分解に関するの実験的研究

In order to confirm the hydrate characteristics the methane hydrate was formed under the conditions in sediments of simulated deep sea floor, at the natural interface of methane gas and water and with the forced stirring of gas and water. Formed hydrate was dissociated under conditions of depressurization and heating. The self preservation effects were tested after freezing to a lower temperature and gas stability in the hydrate was confirmed by burning the dissociated methane gas. As the results some features were obtained. To expedite a quick forming of hydrate heat absorption as well as stirring of gas and water are inevitable. Both of heating or depressurization is effective for dissociation but each presents different phenomena. Self preservation effect could be improved by selecting a suitable freezing temperature.

Cultivation of fungi under simulated deep sea conditions

In order to investigate the barotolerance of marine fungi and to elucidate their ecological role in the deep sea, high-pressure equipment was built and tested. Cultures of the marine yeasts Debaryomyces hansenii, Rhodotorula rubra and Rhodosporidium sphaerocarpum were inoculated into gas-permeable plastic foil bags and incubated in pressure vessels filled with hydraulic fluid that serves also as an oxygen reservoir. The equipment was used at temperatures from 7° to 34°C and pressures from 0.1 to 80.0 MPa. Comparison of five types of plastic foil showed effects on total cell number in batch culture. An exchange of the hydraulic fluid increased yield by replenishing oxygen, the growth-limiting factor. There were no detectable growth differences between buffered (TRIS, HEPES, imidazole, MES) and unbuffered media and thus unbuffered medium was used. Yeasts were best cultivated in an unbuffered sea-water medium (glucose—peptone—yeast extract) sealed in bags made from polyethylene foil. The fluorocarbon liquid FC-77 provided the best oxygen reservoir owing to its high oxygen and carbon dioxide solubility. An exchange of the hydraulic fluid is not necessary if sensitive growth determination methods are used. All marine yeasts cultivated under simulated deep sea conditions were able to grow at least up to a pressure of 20 MPa, with Rhodotorula rubra and Rhodosporidium sphaerocarpum growing at 40 MPa, corresponding to 4000 m depth. Thus, marine yeasts are able to grow under simulated deep sea conditions and may participate in the degradation of organic matter in the deep sea.

An Experimental Approach for Studying the Stability of Organic Compounds under Simulated Submarine Hydrothermal Conditions

Sub-seafloor hydrothermal systems have been proposed as likely environments for chemical evolution and the origin of life. However, a controversy exists as to whether or not amino acids and other organic compounds that are essential to life processes can be formed under hydrothermal conditions. It has been argued in the literature that at high temperatures organic compounds are highly unstable and decompose rapidly. Thermodynamic calculations on the other hand, indicate that organic substances may exist in metastable equilibrium in high temperature environments of the lithosphere. Previous stability studies of organic compounds and abiotic synthesis experiments have only been partly successful in simulating natural hydrothermal systems. This contribution describes a recently developed experimental approach for the study of the stability of amino acids under simulated deepsea hydrothermal conditions.

Maintenance of abyssal benthic foraminifera under high pressure and low temperature: some preliminary results

Abyssal benthic foraminifera have been maintained alive for periods of several weeks under laboratory simulated deep-sea conditions of high pressure and low temperature. In separate experiments, bacterial-sized fluorescent microspheres and three species of microalgae were supplied as food particles. Subsequent light and electron microscopy showed that the algae had been ingested by several foraminiferal species. Furthermore, the fine structure of the foraminiferal cytoplasm was well-preserved which indicates, along with the ingestion of algal food, that they had remained in a viable condition during the incubation. Other observations indicate that abyssal benthic foraminifera ingest naturally occurring photosynthetic cells carried to the deep-sea bed by rapidly sedimenting aggregates. The ability to keep foraminifera originating from depths exceeding 4000 m alive in the laboratory paves the way for the experimental investigation of some important issues in deep-sea biology and palaeoceanography.

Influence of hydrostatic pressure on the moisture absorption of glass fibre-reinforced polyester

The moisture absorption characteristics of glass fibre-reinforced polyester in simulated deep sea water environments have been investigated. Test panels of unsaturated isopthalic polyester resin reinforced with woven E-glass were prepared by hand lay-up and the mass gain occurring during immersion in sea water pressurized up to 80 MPa was monitored. Moisture ingress followed a modified form of Fick's second law of diffusion. The saturation moisture content was shown to be linearly dependent upon the vapour pressure equivalent of hydrostatic pressure. In the case of diffusivity, a systematic relationship with hydrostatic pressure was not observed.

Experimental investigation of hydrate formation behaviour of a natural gas bubble in a simulated deep sea environment

A vertically flowing, closed circuit, high pressure water tunnel was designed and constructed for holding individual gas bubbles stationary against an opposing flow for detailed observations. Hydrate formation behavior of natural gas bubbles was studied at constant pressure as well as under conditions of controlled decompression designed to simulate buoyant rise of the bubble. A bubble of simulated natural gas suspended in 3°C salt water formed hydrates when the pressure was 4826 kPa or higher. The simulated decompression accompanying buoyant rise had very little effect on hydrate formation behavior of a bubble starting from a pressure of 5516 kPa or above. At lower starting pressures, a slight increase in the reaction rate was detected in the initial stages of a run. The conversion of the simulated natural gas to hydrates was complete in runs starting from a pressure of 4826 kPa or above.

Survival of Human Enteric and Other Sewage Microorganisms Under Simulated Deep-Sea Conditions

The survival of pure cultures of Escherichia coli, Streptococcus faecalis, Clostridium perfringens , and Vibrio parahaemolyticus under simulated deep-sea conditions of low temperature (4 C), seawater, and hydrostatic pressures ranging from 1 to 1,000 atm was determined over a period exceeding 300 h. The viability of E. coli and total aerobic bacteria in seawater-diluted raw sewage subjected to these deep-sea conditions was also measured. There was a greater survival of both E. coli and S. faecalis at 250 and 500 atm than at 1 atm at 4 C. S. faecalis was quite insensitive to 1,000 atm, whereas with E. coli there was a 10-fold die-off per 50-h exposure to 1,000 atm. In contrast, V. parahaemolyticus and C. perfringens were quite sensitive to pressures exceeding 250 atm, and with both of these species there was a total loss of viability of approximately 10 8 cells per ml within 100 h at 1,000 atm and within 200 h at 500 atm. The viability of the naturally occurring fecal coliforms in sewage exposed to moderate pressures at 4 C was found to be similar to the survival patterns demonstrated with pure cultures of E. coli . The total numbers of aerobic bacteria in these sewage samples, however, stabilized at 500 and 1,000 atm after 100 h, and at 1 and 250 atm there was significant growth of sewage-associated bacteria, which apparently utilized the organic compounds in the seawater-diluted sewage samples. A preliminary classification of some of these bacteria indicated that approximately 90% (160 isolates) of the organisms that survived over a 400-h exposure to 500 and 1,000 atm were Arthrobacter/Corynebacterium species, and the representative organisms capable of growing at 1 and 250 atm in seawater at 4 C were gram-positive cellulose digesters and an unidentified gram-negative coccus. The significance of these results with respect to the contamination of the deep ocean with human pathogens and the possibility of sewage-associated microorganisms growing and competing with indigenous marine microbial flora in situ is discussed.

Survival of Human Enteric and Other Sewage Microorganisms Under Simulated Deep-Sea Conditions1

The survival of pure cultures of Escherichia coli, Streptococcus faecalis, Clostridium perfringens, and Vibrio parahaemolyticus under simulated deep-sea conditions of low temperature (4 C), seawater, and hydrostatic pressures ranging from 1 to 1,000 atm was determined over a period exceeding 300 h. The viability of E. coli and total aerobic bacteria in seawater-diluted raw sewage subjected to these deep-sea conditions was also measured. There was a greater survival of both E. coli and S. faecalis at 250 and 500 atm than at 1 atm at 4 C. S. faecalis was quite insensitive to 1,000 atm, whereas with E. coli there was a 10-fold die-off per 50-h exposure to 1,000 atm. In contrast, V. parahaemolyticus and C. perfringens were quite sensitive to pressures exceeding 250 atm, and with both of these species there was a total loss of viability of approximately 10(8) cells per ml within 100 h at 1,000 arm and within 200 h at 500 atm. The viability of the naturally occurring fecal coliforms in sewage exposed to moderate pressures at 4 C was found to be similar to the survival patterns demonstrated with pure cultures of E. coli. The total numbers of aerobic bacteria in these sewage samples, however, stabilized at 500 and 1,000 atm after 100 h, and at 1 and 250 atm there was significant growth of sewage-associated bacteria, which apparently utilized the organic compounds in the seawater-diluted sewage samples. A preliminary classification of some of these bacteria indicated that approximately 90% (160 isolates) of the organisms that survived over a 400-h exposure to 500 and 1,000 atm were Arthrobacter/Corynebacterium species, and the representative organisms capable of growing at 1 and 250 atm in seawater at 4 C were gram-positive cellulose digesters and an unidentified gram-negative coccus. The significance of these results with respect to the contamination of the deep ocean with human pathogens and the possibility of sewage-associated microorganisms growing and competing with indigenous marine microbial flora in situ is discussed.