• Corrosion Science and Technology
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• v.16 no.6
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• pp.285-293
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• 2017

The effects of sulfate reducing bacteria (SRB) on the corrosion and scaling of the Q235 carbon steel has been investigated in the simulated sewage water and oil field gathering pipelines production water, using scanning electron microscopy (SEM), energy dispersive x-ray spectrometry (EDS), and three-dimensional stereoscopic microscope. Results indicated that the concentration of SRB reached the maximum value on the ninth day in simulated sewage water with a large amount of scaling on the surface of specimen. In oil field gathering pipelines, a large amount of scaling and mineralization of mineral salts and thick deposition of extracellular polymeric substance (EPS) layers were also observed on the surface of specimen. The thickness of biofilm was about $245{\mu}m$ within 30 days. After adding microbicides, the thickness of corrosion products film was only up to $48-106{\mu}m$ within 30 days, suggesting that SRB could induce biomineralization. Under-deposit corrosion morphology was uniform in the absence of microbicides while local corrosion was observed in the presence of microbicides.

• Corrosion Science and Technology
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• v.18 no.2
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• pp.55-60
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• 2019

Corrosion failure in the convection part of peak load boiler (PLB) of the district heating system led to water leakage. Herein, Internal Rotary Inspection System (IRIS) inspection was employed to examine wall thinning and the cause of leakage in the flue tube. The corrosive products of the turbulator and tube were investigated using scanning electron microscope combined with energy dispersive spectroscopy, X-ray diffraction, and inductively coupled plasma (ICP). Majority of the serious corrosion damage was observed near the turbulator located in the upper flue tube. ICP analysis of the boiler water revealed oxide formation of sodium chloride in the lower end part of the flue tube. A cross-sectional view of the turbulator revealed the presence of double-layers of the oxide film, indicating environmental change during operation associated with water leakage. The outer surface of the turbulator consisted of the acid oxides such as $NO_x$ and $SO_x$ along with sodium and chloride ions. Dew-point corrosion is hypothesized as the main cause for the formation of acid oxides in the region of contact of the flue tube and the turbulator.

• KSBB Journal
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• v.18 no.5
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• pp.393-397
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• 2003

The effect of corrosion inhibitors on antimicrobial activity of biocides (Kathon 886 MW, Triadine 3, Triadine 10 and Grotan BK) was investigated using the Pseudomonas aeruginosa which frequency of occurrence in contaminated fluids is very high and its growth and survival is excellent. When a biocide was used with a corrosion inhibitor, the antimicrobial activity of it was affected by the corrosion inhibitor used. The antimicrobial activity of Kathon 886 MW increased when corrosion inhibitor (each of SS 510, MEA) was used. Triadine 3, Triadine 10, Grotan BK showed the similar trend of antimicrobial effect for the corrosion inhibitors used. Their antimicrobial activities increased when the corrosion inhibitor such as CP-105, CP-E-7 and MEA was used individually. The antimicrobial activity of each corrosion inhibitor was also compared. The results showed that CP-E-7 and MEA was bioresistant and the other corrosion inhibitors were biosupportive. The antimicrobial activity of biocides was in the order of Triadine 10 < Triadine 3 < Kathon 886 MW < Grotan BK.

• Corrosion Science and Technology
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• v.22 no.2
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• pp.90-98
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• 2023

In this study, cobalt oxide (Co₃O₄) and cobalt-doped magnetite (CoFe₂O₄) nanoparticles were synthesized by a hydrothermal method. They were then used as corrosion inhibitors for corrosion protection of AA2024-T3 aluminum alloys. These obtained nanoparticles were characterized by x-ray diffraction, field-emission scanning electron microscopy, and Zeta potential measurements. Corrosion inhibition activities of Co₃O₄ and CoFe₂O₄ nanoparticles were determined by performing electrochemical measurements for bare AA2024-T3 aluminum alloys in 0.05 M NaCl + 0.1 M Na₂SO₄ solution containing Co₃O₄ or CoFe₂O₄ nanoparticles. Corrosion protection for AA2024-T3 aluminum alloys by a water-based epoxy with or without the synthesized Co₃O₄ or CoFe₂O₄ nanoparticles was investigated by electrochemical impedance spectroscopy during immersion in 0.1 M NaCl solution. The corrosion protection of epoxy coating deposited on the AA2024-T3 surface was improved by incorporating Co₃O₄ or CoFe₂O₄ nanoparticles in the coating. The corrosion protection performance of the epoxy coating containing CoFe₂O₄ was higher than that of the epoxy coating containing Co₃O₄.

• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.3
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• pp.283-293
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• 2015

In order to evaluate corrosion resistance of steel fiber-reinforced concrete, accelerated chloride migration and surface resistivity tests were conducted. In addition air content of fresh concrete, compressive strength and water absorption were measured for investigating fundamental characteristics of concrete. Two different water-cement ratios(0.44, 0.5) and three steel fiber contents(0.25%, 0.5%, 1%) were considered as variables. Note that all specimens cast with same compaction work. As a results, corrosion resistance decreased as steel fiber contents increased regardless of water-cement ratio when the concrete was compacted with same amount of work done. However, for concrete with same steel fiber content, the lower water-cement ratio showed the better corrosion resistance. It is found that enhancement of fluidity and enough compaction should be done for corrosion resistance of SFRC.

• Corrosion Science and Technology
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• v.9 no.5
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• pp.187-195
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• 2010

Hyper duplex stainless steels have been developed in Korea for the purpose of application to the seawater system of Korean nuclear power plants. This system supplies seawater to cooling water heat exchanger tubes, related pipes and chlorine injection system. In normal operation, seawater is supplied to heat exchanger through the exit of circulating water pump headers, and the heat exchanged sea water is extracted to the discharge pipes in circulating water system connected to the circulating water discharge lines. The high flow velocity of some part of seawater system in nuclear power plants accelerates damages of components. Therefore, high strength and high corrosion resistant steels need to be applied for this environment. Hyper duplex stainless steel (27Cr-7.0Ni-2.5Mo-3.2W-0.35N) has been newly developed in Korea and is being improved for applying to nuclear power plants. In this study, the physical & mechanical properties and corrosion resistance of newly developed materials are quantitatively evaluated in comparative to commercial stainless steels in other countries. The properties of weld & HAZ (heat affected zone) are analyzed and the best compositions are suggested. The optimum conditions in welding process are derived for ensuring the volume fraction of ferrite(${\alpha}$) and austenite(${\gamma}$) in HAZ and controlling weld cracks. For applying these materials to the seawater heat exchanger, CCT and CPT in weldments are measured. As a result of all experiments, it was found that the newly developed hyper duplex stainless steel WREMBA has higher corrosion resistance and mechanical properties than those of super austenitic stainless steels including welded area. It is expected to be a promising material for seawater systems of Korean nuclear power plants.

• Journal of Korean Society of Water and Wastewater
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• v.25 no.6
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• pp.839-846
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• 2011

To investigate corrosivity characteristics of raw water in Korea, Langelier index (LI) of 30 multi-regional water treatment plants (WTPs) were evaluated. Annual average values of LI at 30 WTPs were all negative, which means raw water in Korea is very corrosive. LI results for 4 major rivers showed that raw water from Han and Nakdong had relatively high values compared to those of Sumjin and Keum. On the other hand, LI values of raw water from the tributaries of four major rivers were relatively low presumably due to geological characteristics, and in some cases the values were less than -4.0 which means increase of LI is urgently needed to minimize red water problem. Based on the correlation results among LI and water quality parameters, pH, water temperature, calcium concentration were confirmed as major components for LI. Therefore, pH and calcium concentration control is an effective method for the improvement of LI in water treatment processes.

• 수도
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• s.70
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• pp.48-56
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• 1994

• Corrosion Science and Technology
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• v.17 no.3
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• pp.116-122
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• 2018

The secondary coolant of a nuclear power plant has small amounts of various impurities (S, Pb, and Cl, etc.) introduced during the initial construction, maintenance, and normal operation. While the concentration of impurities in the feed water is very low, the flow of the cooling water is restricted, so impurities can accumulate on the Top of Tubesheet (TTS). This environment is chemically very complicated and has a very wide range of pH from acidic to alkaline. In this study, the characteristics of the oxide and the mechanism of stress corrosion cracking (SCC) are investigated for Alloy 690 TT in alkaline solution containing Pb, Cl, and S. Reverse U-bend (RUB) specimens were used to evaluate the SCC resistance. The test solution comprises 3m NaCl + 500ppm Pb + 0.31m $Na_2SO_4$ + 0.45m NaOH. Experimental results show that Alloy 690 TT of the crevice environment containing Pb, S, and Cl has significant cracks, indicating that Alloy 690 is vulnerable to stress corrosion cracking under this environment.

• Journal of Surface Science and Engineering
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• v.45 no.1
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• pp.25-30
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• 2012

The galvanostatic tests for corrosion protection are conducted at various applied current densities during 93,600 sec, and evaluated in terms of the variations in current density with time and in the potential at the applied current density. In addition, the corrosion damage depth is analyzed with 3D analysis optical microscope after galvanostatic tests. In this study, it was investigated to decide condition of the corrosion protection gavalnostatic method for Cu-Al alloy that has an excellent corrosion resistance. In the galvanostatic test under the cavitation environment, the energy was reflected or cancelled out by the collision with the oxygen gas generated by the oxygen reduction action. The surface observation showed neither the cavitation damage nor the electrochemical damage in the current density over 0.01 $A/cm^2$ in the dynamic state under the cavitation environment.