• Environmental Engineering Research
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• v.23 no.2
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• pp.164-174
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• 2018

Corrosion of copper alloys (copper, bronze and brass) in soil was evaluated at ambient temperature using various methods such as electrochemical impedance spectroscopy (EIS), polarization curves and Scanning Electron Microscopy (SEM) coupled with Energy Dispersive Spectroscopy microanalysis measurements. Three equivalent circuits were separately used to interpret the obtained impedance spectra. The EIS measurements indicated that the polarization resistance of all electrodes increases with increasing the immersion time. SEM showed a presence of three layers of corrosion products with various composition and morphology covering each electrode. In addition, it was found that at 20% of moisture content the $R_p$ values and the current density of all electrodes in the studied soil give the following order: copper > bronze > brass. Good consistency between the data obtained from EIS and PP measurements was observed.

• Nuclear Engineering and Technology
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• v.50 no.1
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• pp.1-17
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• 2018

This article reviews the multiscale nature of stress corrosion cracking (SCC) observed by high-resolution characterizations in austenite stainless steels and Ni-base superalloys in light water reactors (including boiling water reactors, pressurized water reactors, and supercritical water reactors) with related opinions. A new statistical summary and comparison of observed degradation phenomena at different length scales is included. The intrinsic causes of this multiscale nature of SCC are discussed based on existing evidence and related opinions, ranging from materials theory to practical processing technologies. Questions of interest are then discussed to improve bottom-up understanding of the intrinsic causes. Last, a multiscale modeling and simulation methodology is proposed as a promising interdisciplinary solution to understand the intrinsic causes of the multiscale nature of SCC in light water reactors, based on a review of related supporting application evidence.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.2
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• pp.493-499
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• 2008

This study was performed to estimate the water quality parameters on corrosion such as pH, turbidity, Fe released concentration, corrosion rate by using batch reactor for corrosion control of phosphate corrosion inhibitor in carbon steel pipes. The pH, conductivity, alkalinity, and Ca hardness showed a slight change for dosing the phosphate corrosion inhibitor with carbon steel pipe in batch reactor. The turbidity was about ten times lower with 5 mg $P_2O_5/L$ of the corrosion inhibitor than that without. The Fe released concentration and corrosion rate was decreased by about 12.2, 24 times with 5 mg $P_2O_5/L$ of the corrosion inhibitor than that without. In conclusion, the optimum concentration of the phosphate corrosion inhibitor was found to be 5 mg $P_2O_5/L$. The effect of the corrosion inhibitor was significant for the carbon steel plate samples tested in this study. The corrosion inhibitor can be an effective cure for corrosion and red water problem preventing the service pipe from further corrosion.

• Plant Journal
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• v.4 no.2
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• pp.60-65
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• 2008

As the operating conditions in a supercritical oxidation reactor are set in high temperature with high pressure causing a reactor suffering from the harsh circumstances. It means the reactor adopts itself with Fe-Cr alloy in acidic atmosphere with low pH value and Ni alloy in basic atmosphere with high pH value due to its superior corrosion resistance. The study, whose target waster water is pertinent to the latter part, has selected Ni alloy such as ostenite type stainless steel 304 and 316, superstainless steel AL6XN, Inconel 625, MAT 21, and titanium Gr. 5 in order to measure corrosion resistance against those samples under the same conditions of temperature and pressure applied for a supercritical oxidation reactor. The result shows the identifiable difference in corrosion resistance by observing the surface states through a scanning probe microscope as well as measuring the weight loss through making the samples above deposited in wastewater for two-week and four-week stay. The purpose of this corrosion experiment is to identify the most corrosion-resistant material among sample species pre-selected according to pH concentration of wastewater in pursue of applying for a reactor exposed to the extreme corrosion environment. It is because such a reactor made of a verified material enables to safeguard a stable operation under the supercritical wastewater processing facility.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.36 no.2
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• pp.132-138
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• 2000

The effect of fluid flow on corrosion and erosion-corrosion of metal is a well-recognized phenomenon in pipelines and machinery equipment, and so on. Not only are fluid hydrodynamics important, but also the corrosiveness of the process or production stream affects the corrosion system. Recent research demonstrates that it is possible to erosion-corrosion(E/C) phenomena in terms of hydrodynamics, electrochemical corrosion kinetics and film growth/removal phenomena. Stress corrosion cracking behavior under cavitation erosion-corrosion of mild steel(SS41) was investigated of base metal and weldment under loaded stress. Main result obtained are as follows : 1) The cavitation erosion sensitivity of base metal affected weight loss is more susceptive than heat affected zone, 2) The corrosion sensitivity affected weight loss of welding heat cycle is less susceptive on stress corrosion under cavitation erosion-corrosion than stress corrosion.

• Corrosion Science and Technology
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• v.18 no.6
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• pp.228-231
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• 2019

Aluminum and its alloys have been widely used in various fields because of low weight, high strength, good conductivity, and low price. It is well known that aluminum alloys that cause natural oxide film can inhibit corrosion in wet, salty environments. However, these oxides are so thin that corrosion occurs in a variety of environments. To prevent this problem, an electrochemical anodizing technique was applied to the aluminum alloy surface to form a thick layer of oxide and a unique oxide shape, such as a hierarchical pore structure simultaneously combining large and small pores. The shape of the structures was implemented using stepwise anodization voltages such as 40 V for mild anodizing and 80 V for hard anodizing, respectively. To maximize water repellency, it is crucial to the role of surface structures shape. And a hydrophobic thin film was coated by 1H, 1H, 2H, 2H-Perfluorodecyltrichlorosilane (FDTS) to minimize surface energy of the structure surface. Thus, such nanoengineered superhydrophobic surface exhibited a high water contact angle and excellent corrosion resistance such as low corrosion current density and inhibition efficiency.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2001.11a
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• pp.92-97
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• 2001

This paper was studied on the effect of temperature on corrosion of absorption refrigeration systems using LiBr-$H_2O$ working fluids. In the fresh water and 62 %lithium bromide solution at $70^{\circ}C$, polarization test of SS 400, Cu(Cl220T-OL) and Ni-Al bronze was carried out. And Polarization behavior, polarization resistance characteristics, corrosion rate(mmpy) and corrosion sensitivity of materials forming absorption refrigeration systems was considered. The main results are as following: As the experimental temperature increase, the change of corrosion rate of Ni-Al bronze become duller than SS 400 and Cu in 62 % lithium bromide solution. Open circuit potential of SS 400 is less noble than that of Cu and Ni-Al bronze in fresh water, but that becomes noble than Cu and Ni-Al bronze in 62 % lithium bromide solution. The corrosion sensitivity of Ni-Al bronze was controlled than that of Cu and SS 400 in 62% LiBr solution.

• Advances in concrete construction
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• v.15 no.1
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• pp.1-10
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• 2023

Concrete is one of the most widely used structure materials. Concrete is like the motor of the construction industry. The remarkable feature of this Concrete is its cheapness and low energy consumption. Concrete alone does not show resistance against any force but only against compressive forces. Therefore, steel rebar product is used as a reinforcement and increase the strength of Concrete. It can be done by putting rebar in Concrete in different ways. Rebar rusting is one of the crucial symptoms that cause swift destruction in reinforced structures-factors such as moisture in concrete increase the steel corrosion rate. In most cases, it is difficult to compensate for the damage caused by the corrosion of base metals, so preventing corrosion will be much more cost-effective. Coatings made with nanotechnology can protect Concrete against external degradation factors to prevent water and humidity from penetrating the Concrete and prevent rusting and corrosion of the rebar inside. It prevents water penetration and contamination into the Concrete and increases the Concrete's quality and structural efficiency. In this research, silica and titanium dioxide nanoparticle coatings have been used due to their suitable electrical and thermal properties, resistance to oxidation, corrosion, and wear to prevent the corrosion of rebars in Concrete. The results of this method show that these nanoparticles significantly improve the corrosion resistance of rebars.

• Corrosion Science and Technology
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• v.15 no.3
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• pp.135-140
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• 2016

Piping and equipment are degraded by flow-accelerated corrosion (FAC) in nuclear power plants. FAC causes numerous problems and nuclear utilities maintain programs to control FAC. The key parameters influencing FAC are hydrodynamic conditions, water chemistry, and effect of materials. Recently, a nuclear utility has planned slight power uprates in Korea. Operating conditions need to be changed in the secondary system according to power uprates. This study analyzed the effect of wall-thinning caused by power uprates. The change of operation data in the secondary cycle is reviewed, and wall-thinning rates are analyzed in the main lines. As a result, two phase (mixture of water and steam) lines have a greater impact than a water line under power uprate conditions. Also, the quality of steam is the most important factor for FAC in two phase lines.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.04a
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• pp.348-353
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• 1996

This study addresses the evaluation of the durability of reinforced concrete marine structures subjected to fatigue loading. The laboratory investigation was carried out on full and half size reinforced concrete specimens with three different water cement ratios (0.3, 0.4, and 0.56), static and fatigue loading conditions, and epoxy-coated and regular black steel reinforcements. The marine tidal zone was simulated by alternate filling and draining of the tank (wet and dry cycled), and a galvanostatic corrosion technique to accelerate corrosion of reinforcement was used. Half-cell potentials and changes of crack width were measured periodically during the exposure and followed by ultimate strength testing. The significant findings include adverse effect of fatigue loading, existence of an explicit size effect, poor performance of epoxy coated steel, and negative effect of increasing water/cement ratio.