• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.649-652
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• 2006

This paper describe the performance of seawater purification, to which living organisms can adapt, and the physical properties of porous concrete with continuous void. Although conventional concrete has been regarded as a destroyer of nature, seawater and air can pass freely through concrete when it is made porous by forming continuous void. This not only enables plants to vegetables, but also makes it possible for microscopic animals and plants, including bacteria, to attach to and inhabit uneven surface as well as internal voids when the concrete is provided in a natural seawater area or seawater side area. As a result, porous concrete using recycled aggregate improved the performance of seawater purification. In this study, The performance of seawater purification of porous concrete using recycled aggregate analyzed by T-P, T-N.

• Journal of Conservation Science
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• v.28 no.4
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• pp.329-341
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• 2012

Magai Wareiishi Jizo (Buddhist statue carved on rock surface) is close to shoreline and a part of rock block is periodically immersed by seawater. Rock material of the Wareiishi-jizo statue is composed mainly of medium or coarse-grained biotite granite and very durable. However, physical properties of the rock have been changed according to the complex interactions of the salt solution and surrounding environment. Exfoliation of the rock surface is a serious condition by salt crystallization. Exfoliation (14.6%) is concentrated on the upper part of the rock block with mainly boundary of seawater as the center. On the other hand, lower part of the rock block show black layers by contaminants deposition. In addition, brown discoloration and biological contaminants is overlapped. Rock surface show high discoloration rate of 50.5% (black discoloration, 29.2% > yellow discoloration, 14.1% > brown discoloration, 4.4% > green discoloration, 2.9%). Upper part of the rock block had a lot of change in the physical properties than lower part that is immersed by seawater. In particular, surface properties of the rock block was very weak state at the boundary surface of seawater permeation.

• Corrosion Science and Technology
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• v.17 no.4
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• pp.176-182
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• 2018

Corrosion of the Cu alloy with 10wt% Ni in stagnant seawater with residual free chlorine was investigated. Despite that fact that Cu alloys are widely used for seawater applications due to their stubborn resistance to chloride attack, not much is known as to how the residual free chlorine in seawater affects corrosion of Cu and its alloys. In this work, immersion tests were conducted in the presence of different levels of chlorine for 90-10 Cu-Ni samples, one of the most frequently used Cu alloys for seawater application, mostly in shipbuilding. The results revealed no evidence for accelerated corrosion of the Cu-Ni alloy even in the presence of 5 ppm residual chlorine in seawater, signifying that the Cu-Ni alloy can be more tolerant to residual chlorine that has been commonly cited by the shipbuilding industry. However, comparison of polarization behavior of the alloy samples in the presence of different electrolytes with different concentrations of residual chlorine suggests that higher concentration of chlorine could increase the corrosion rate of the Cu-Ni alloy. Furthermore, it is suggested that microorganisms in the seawater could increase the corrosion rate of the Cu-Ni alloy by encouraging exfoliation of the corrosion product off the metal surface.

• Journal of Ocean Engineering and Technology
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• v.23 no.6
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• pp.39-43
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• 2009

A flow and low temperature of deep seawater the biofouling properties in a seawater environment of different materials, such as a steel pipe, polyethylene pipe, and nylon net, used for ocean industries. Experiments in a real sea environment were performed to grasp the quantitative and qualitative biofouling from diatoms attached to materials by measuring the Chlorophyll-a density. Experimental samples were placed under five types of ocean environmental conditions and analyzed every month for five months. It is shown that the biofouling by diatoms was strongly affected by the seawater temperature for all of the experimental samples. It was found that diatoms mainly adhered to the nylon net, while crustaceans prefer polyethylene, under a high temperature condition. It is believed that the biofouling properties are strongly related to the surface roughness of a material. The biofouling under the low temperature condition of deep seawater was rare and stable for the experimental periods. The inside of a pipe conveying deep seawater can be presumed to remain clear without biofouling on the condition of a flow and low temperature of deep seawater.

• Geophysics and Geophysical Exploration
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• v.3 no.3
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• pp.101-111
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• 2000

In order to assess the seawater intrusion, induction, temperature and conductivity of fluid, and natural gamma logs were obtained in nine wells at the three study areas having different hydrogeologic characteristics. Besides surface geophysical exploration, supplementary geophysical well logs were carried out to understand the hydrogeological characteristics related to the seawater intrusion in the study areas. The geophysical well logs have been proved to increase the accuracy of interpretation of the surface geophyscial exploration's data for assessment of seawater intrusion, and to get the optimum depth for a long monitoring of groundwater. They, also, revealed that the identification of hydrogeological units for strata's porosity was able to be achieved and were illustrated the applicability of geophysical well logs monitoring. Finally, geophysical well logs are expected to play to get the more quantitative information of seawater infusion, if it is fully collaborated with a better method that is strata's resistivity determination with not relatively much effected by seawater within the drilled borehole and that is the porosity measurement with built on small diameter PVC casing.

• Journal of the Korean Society of Marine Environment & Safety
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• v.17 no.2
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• pp.105-121
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• 2011

The operation of tidal power facility may induce severe changes of water quality in Shihwa Lake. Current water quality data are quite important to water quality management policy of Shihwa Lake. Thus, the water quality data of Shihwa Lake and its adjacent sea in 2010 were presented to characterize the temporal and spatial changes of water parameters such as pH, SS, DO, COD, dissolved nutrients, chlorophyll-a, TN and TP. Highest levels of water quality parameters were observed near the Shihwa and Banweol industrial complexes and the levels of water quality parameters were on a decreasing trend to those near the water gate. It suggests that the horizontal distributions of water quality levels are mainly controlled by the supply of fresh water from streams and the inflow of outer seawater by operation of water gate. Although the higher concentrations of TN and TP were observed in the location being affected by Sorae port, the levels of water quality parameters in outer sea of Shihwa Lake were lower than those in Lake. In summer season, hypoxic condition was well developed in bottom water by strong stratification and active decomposition of organic matter. Thus, the vertical distributions of dissolved nutrient, TN and TP concentrations showed the concentrations to be higher in bottom seawater than those in surface seawater whereas the vertical distributions of chlorophyll-a, COD and POC concentrations showed the concentrations to be higher in surface seawater than those in bottom water. Results of Pearson's correlation matrix for surface seawater demonstrated that salinity showed negatively good correlation with not only dissolved nutrients except for ammonium but chlorophyll-a, COD and POC This result indicates that the supply of dissolved nutrients through several streams might significantly affect phytoplankton bloom and increase of COD concentration in surface seawater.

• Ocean Science Journal
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• v.43 no.4
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• pp.223-232
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• 2008

In order to determine the temporal and spatial variations of nutrient profiles in the shallow pore water columns (upper 30 cm depth) of intertidal sandflats, we measured the salinity and nutrient concentrations in pore water and seawater at various coastal environments along the southern coast of Korea. In the intertidal zone, salinity and nutrient concentrations in pore water showed marked vertical changes with depth, owing to the active exchange between the pore water and overlying seawater, while they are temporally more stable and vertically constant in the sublittoral zone. In some cases, the advective flow of fresh groundwater caused strong vertical gradients of salinity and nutrients in the upper 10 cm depth of surface sediments, indicating the active mixing of the fresher groundwater with overlying seawater. Such upper pore water column profiles clearly signified the temporal fluctuation of lower-salinity and higher-Si seawater intrusion into pore water in an intertidal sandflat near the mouth of an estuary. We also observed a semimonthly fluctuation of pore water nutrients due to spring-neap tide associated recirculation of seawater through the upper sediments. Our study shows that the exchange of water and nutrients between shallow pore water and overlying seawater is most active in the upper 20 cm layer of intertidal sandflats, due to physical forces such as tides, wave set-up, and density-thermal gradient.

• Journal of the Korean institute of surface engineering
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• v.49 no.2
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• pp.172-177
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• 2016

In this paper, various electrochemical experiments were conducted in seawater solution to evaluate corrosion damage behavior of arc thermal sprayed Inconel 625 coating on SS400 steel in marine environment. As a result, corrosion damages of thermal sprayed Inconel 625 coating preferentially occurred at the defect area, and they were observed as a form of pitting corrosion in the galvanostatic experiments. In Tafel analysis, corrosion current density of Inconel 625 coating was relatively high due to influence of interconnected pores and Cr oxides in the thermal spray coating layer. On the other hand, the result of the potential measurement, thermal sprayed Inconel 625 coating should need the post-treatment which can compensate the defects like pores and cracks because Inconel 625 coating presented a higher potential of about 290 mV than that of the SS400 steel.

• Journal of the Korean Society of Marine Environment & Safety
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• v.5 no.2
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• pp.57-65
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• 1999

The in situ observations and the seawater analyses were conducted at all seasons from July 1996 to April 1999 for the purpose of describing the characteristics of seasonal variations of water quality in Mokpo harbour, Korea. Vertical stratification started to be formed in water column in spring, developed in summer and disappeared in fall. In summer, vertical density distribution of water column was found to be in stable structure with lower temperature and higher salinity of bottom water, and the vertical mixing of water between surface and bottom layers was restricted. In winter, however, surface water was found to be similar to bottom water in temperature and salinity, and water column was in unstable structure and in well-mixed condition between surface and bottom waters. The saturation percentage of dissolved oxygen(DO) in bottom water of inner part of Mokpo harbour at all seasons was shown to be decreased to the third grade or under the third grade of Korean standards of seawater quality. In particular, dissolved oxygen was oversaturated in surface water and undersaturated in bottom water in summer, due to stratification and organic pollution. The difference of DO concentration between surface and bottom waters was found to be greater in spring and summer than in fall and winter, due to stratification and photosynthesis of phytoplankton. The concentrations of chemical oxygen demand(COD) over the entire waters of Mokpo harbour were found to fluctuate from below the third grade to the first grade of Korean standards through all seasons and COD concentrations of same seasons were shown to be different year after year. In particular, in view of COD, the annual average seawater quality of Mokpo harbour was evaluated to be in third grade of Korean standards, due to organic pollution. The average COD of surface water was greater than that of bottom water in spring and summer, due to the autochthonous COD caused by production of phytoplankton in surface waters, while the average COD of surface water was similar to that of bottom water in fall and winter, due to the vertical mixing of water between surface and bottom layers.

• Journal of the Korean institute of surface engineering
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• v.53 no.5
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• pp.219-226
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• 2020

This paper investigated the characteristics of anodized aluminum 6061-T6 alloy for corrosion and stress corrosion cracking(SCC) under natural seawater. The hard anodizing oxide film formed on the 6061-T6 was a uniform thickness of about 25 ㎛. The corrosion characteristics were performed with a potentiodynamic polarization test. SCC was characterized by a slow strain rate tensile test under 0.005mm/min rate. As a result, the anodizing film showed no significant effect on SCC in the slow strain rate test. However, the corrosion current density of base metal was measured to be approximately 13 times higher than that of the anodized specimen. Therefore, the anodizing film significantly improved the corrosion resistance of 6061-T6 alloy in natural seawater.