• Journal of the Korean Society of Industry Convergence
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• v.27 no.5
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• pp.1099-1109
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• 2024

As a wide range of industries using iron, such as water and sewerage pipes, gas pipelines, heat pipes, electric engines, communication pipes, and oil pipelines, rapidly become active, there is a demand for reliability and low cost of DC power supplies that can prevent corrosion of pipe networks. In particular, high-efficiency corrosion prevention systems due to changes in the perception of carbon emissions and energy saving are essential elements. Therefore, the construction of a switching-type corrosion current controller is being activated. Also, in such systems, DC/DC converters capable of multi-channel current control are demanded for corrosion prevention functions and uniform consumption of sacrificial anodes. This paper proposes a new current supply system for preventing pipeline corrosion using a low-cost SMPS dedicated chip. The proposed method can maintain excellent parallel operation function, protection function, and response speed by configuring a current controller using a hybrid method using analog and digital. The proposed method verified its superiority through simulations and experiments.

• Corrosion Science and Technology
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• v.21 no.5
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• pp.327-339
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• 2022

The water-jet technique started by Bridgman can cut metal and alloys without harmful gas and fume. However, while this technique is convenient to cut metals and alloys, in the case of coated pipe, water jet induces the degradation of coatings on the pipes, and may facilitate structural failure, leakage, and loss of products. While there are many reports on the effect of water jet on cut metals and the damage of metallic materials, research on the effect of water impingement on the epoxy coatings has been little studied. In this work, we therefore control the velocity of water jet, distance between nozzle and specimen, and water temperature, and discuss the effect of water impingement on the epoxy coatings. Increasing water velocity and water temperature and reducing nozzle distance increased the degradation rates of three epoxy coatings were increased. Among three test parameters - water velocity, nozzle distance and water temperature, water temperature was relatively effective to increase the degradation rate of epoxy coatings.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.3
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• pp.307-313
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• 2022

In this study, the correlation between Half Cell Potential(HCP) and the corrosion influencing factors was analyzed with considering three levels of water-cement ratio, the concentration of chloride solution, and cover depth. As a result of long-term corrosion monitoring, HCP behavior was close to the critical corrosion potential(-350 mV) in all water-cement ratios in the case of 3.5 % and 7.0 % chloride concentration. Regarding the passed charge test in 548 curing days, the passed charge results were improved to 'Moderate' grade. Multiple regression analysis was performed to evaluate the correlation between corrosion influencing factors and HCP, and it was evaluated that the effects of influencing factors to HCP were in the order of chloride concentration, water-cement ratio, and cover depth. In the case of the relationship between HCP and the passed charge, the coefficient of determination showed a high level of 0.9, which yielded a close correlation between the passed charge and HCP.

• Proceedings of the KWS Conference
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• 2003.05a
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• pp.257-259
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• 2003

Sulfide Stress Corrosion Cracking(SSCC) of welded Steel pipe has been investigated. A specimens are stressed into the synthetic sea water saturated with H$_2$S. Therefore SSCC occur at the hardnest point. we are discusses the test methods used for laboratory corrosion testing of welded steel pipe and the results of test.

• Journal of Fisheries and Marine Sciences Education
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• v.15 no.2
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• pp.176-183
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• 2003

Recently, with the tendency of lightening, high-strength and high-speed in the marine industries such as marine structures, ships and propellers, it is rapidly enlarged the use of the aluminium alloy. Therefore, there occurs much interest in the study on corrosion characteristics of aluminium alloy. This paper was studied on the corrosion characteristics of Al-Mg alloy propeller used for a coasting vessel. Under the various pH of marine environment, the corrosion test of Al-Mg alloy was carried out. And thus polarization resistance, corrosion potential, and current density behavior of Al-Mg alloy and galvanic corrosion behavior of Al-brass and Al-Mg alloy coupled Al 5086 and SS 400 for hull were investigated. The main results are as following: 1. The corrosion potential of Al-brass propeller is more nobel than materials for hull, but that of Al-Mg alloy propeller is low or similar to materials for hull. Therefore, the galvanic corrosion of hull due to Al-Mg propeller don't occur. 2. The polarization resistance of Al-Mg alloy in sea water of pH 4 is highest, and corrosion current density of Al-Mg propeller is the most controlled. 3. As pH value decreases, potential showed Evans polarization diagram approaches cathodic potential. The corrosion current density of Al-Mg alloy is controlled to anodic reaction rate, therefore, the corrosion reaction of Al-Mg alloy is anodic control.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.5
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• pp.25-30
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• 2010

The authors have studied on the corrosion resistance of the hot stamped steel sheets for the application to automotive parts. Recently automotive companies have focused on the hot stamped parts to meet the light weighting needs and the safe reason. Because of the cost reduction of the hot stamped parts, automotive companies increase the usage of the coated steel sheets, especially Al-Si coated steel sheets. The coated layer of Al-Si coated steel sheets contains up to 50% of Fe, which was diffused from the steel sheet, after hot stamping. The hot stamped steel sheet was not phosphated due to the oxidation layer of the coating, however, the result of the water resistance test is similar to that of the conventional GA steel sheets. The pitting depth and the weight reduction of the coated layer of hot stamped steel sheets are less than those of GA steel.

• Journal of environmental and Sanitary engineering
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• v.14 no.2
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• pp.75-83
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• 1999

In this research, the has been speculation about effects of pH, alkalinity, and chloride, each of which are major factors in water for the corrosion of copper pipes frequently used as the distribution system throughout the world. It is believed that these factors release a corrosion by-product. The results show the following that the first, for each water sample of pH 7, 8 and 9, various concentrations of alkalinity at 10, 50, 100, 150 mg/L was tested. It was found that conditions of higher pH led to decreased concentrations of copper by-product. For each pH, higher alkalinity produced higher concentrations of copper by-product. the second, higher chloride concentrations led to decreased concentrations of copper by-product. Apparently this was due to the Nantokite(CuCl) formation on the inner walls of the copper pipes with the passage of time. The third, when 25, 50mg/L of chloride were added, the average decreasing rate of copper release concentration was 45.7, 66.7%, respectively.

• Journal of Industrial Technology
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• v.22 no.B
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• pp.13-20
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• 2002

The purpose of this study is to investigate the effect of acid fog on the rust formation behavior of weathering steel (SMA50) which is used in uncoated bridges. Weathering steel didn't form the passive film under the environment of acid fog(pH5,6), whereas the environment of distilled water formed the protective oxide film. Therefore, the construction of weathering steel under the environment extremely exposed to SOx and NOx which are the main compositions of acid fog is not adequate. Fatigue limits of weathering steel under acid fog environment are remarkably decreased as compared with environment of distilled water. The corrosive constituents in acid fog has piled up the corrosion products on specimen surface and generated the corrosion pits. Because of the high stress concentration arising at this corrosion pit, relatively low fatigue limits were obtained for acid fog specimens.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.447-450
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• 2000

Recently, antiwashout underwater concrete has used for underwater structure such as high strength massive concrete structures. When, concrete is placed in seawater the quality and durability of concrete could be doubt to especcially because the amount of cement placed in the concrete can be diminished by flowing seawater. In this study, antiwashout underwater concrete mixed with mineral admixtures for improvement of properties was placed in air, water, and salt water. Half-cell potential and current density was of specimens which made under different conditions measured for estimating corrosion degree. The experimental results demostrate that corrosion resistantce in saltwater was little and mineral admixtures improved properties of concrete.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.1
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• pp.13-20
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• 2008

The purpose of this study is to investigate the effect of acid fog on the rust formation behavior of weathering steel (SMA50) which is used in un-coated bridges. Weathering steel didn't form the passive film under the environment of acid fog(pH5,6), whereas the environment of distilled water formed the protective oxide film. Therefore, the construction of weathering steel under the environment extremely exposed to SOx and NOx which are the main compositions of acid fog is not adequate. Fatigue limits of weathering steel under acid fog environment are remarkably decreased as compared with environment of distilled water. The corrosive constituents in acid fog has piled up the corrosion products on specimen surface and generated the corrosion pits. Because of the high stress concentration arising at this corrosion pit, relatively low fatigue limits were obtained for acid fog specimens.