• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.05a
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• pp.307-308
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• 2021

Corrosion of reinforced steel inside concrete is an important cause of performance degradation of reinforced concrete structures and has a profound influence on the durability of structures. In this study, three groups of different reinforced concrete structures exposed to the natural environment were subjected to chloride ion accelerated corrosion tests for up to 180 days. The corrosion velocity and ambient temperature of the samples were measured and recorded every day. Based on Faraday's law, the corrosion speed of steel bars could be measured, and the ambient temperature and humidity around the structure in corresponding time were compared. Through the measurement of up to 180 days, the influence of external ambient temperature and humidity on the corrosion speed of steel bars inside the concrete structure was found out. The results show that there is a good direct proportional relationship between temperature and corrosion speed. When the ambient temperature increases by 15℃, the corrosion rate increases by about one time.

• Tribology and Lubricants
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• v.18 no.4
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• pp.299-304
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• 2002

This paper reports the studies on the wear-corrosion behavior of ductile cast iron in the acidic environment. In atmosphere and variety of pH solution, specific wear rate and wear-corrosion characteristics of GCD 60 with various sliding speed and distance were investigated. And electrochemical polarization test of GCD 60 was examined in the environment of various pH values. The main results are as following : As the contact pressure increases, the critical velocity of specific wear rate becomes transient at low sliding speed. As pH value becomes low, wear-corrosion loss increases in the aqueous solution. As the corrosion environment is acidified, corrosion potential of GCD 60 becomes noble and corrosion current density increases.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.8
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• pp.974-980
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• 2014

Aluminum acts as sacrificial anode and corrosion protection with Al2O3 formation. If the same current on material for Al ships with steel ships supplies, the more hydrogen would be occurred, that result is bring about over-protection. For this reason, the damage by hydrogen embrittlement leads to the serious accident. In this study, we evaluate electrochemical behavior with rotation speed of 5083-H116 Al alloy material for Al ship in seawater. To examine the electrochemical characteristics with rotation speed and its effects on performance, experiments were conducted at four rotation speed. Results of experiments, the corrosion current density and damage were increased by applying the rotation speed compared to static state.

• Journal of the Korean Society for Railway
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• v.11 no.1
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• pp.107-113
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• 2008

As it recently appears that LCC (Life Cycle Cost) analysis may be considered as an essential method for economic evaluation of infrastructures. Many researches have been made to assess LCC of each facility based on reasonable methods. However, expected maintenance repair cost must be reasonably estimated to enhance the reliability of LCC analysis through systematic and rational methods. This study is intended to propose a rational approach to reliability-based LCC analysis of high-speed railway steel bridges considering lifetime corrosion and fatigue damage. However in Korea, since high speed railway steel bridges are only recently constructed, no direct statistical data are available for the account of the maintenance cost and thus their maintenance characteristics are not clear yet. In this paper, for the assessment of expected maintenance/repair cost, the fatigue system reliability analysis incorporating the corrosion effect is proposed by considering the corrosion and fatigue damage using measured data of high speed railway steel bridges. A model proposed by Rahgozar, of at for fatigue notch factor considering the corrosion effect is used in order to incorporate the corrosion effect into the fatigue strength reduction and S-N curve. Finally, the effectiveness of LCC model proposed for high-speed railway steel bridges is demonstrated by a numerical example.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.82-82
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• 2009

Although leakage at a low carbon steel pipe made by electrical resistance welding(ERW) was reported due to grooving corrosion, the cause for the corrosion has not yet been cleared. So lots of researches were carried out already about grooving corrosion mechanism of ERW carbon steel pipe but there is seldom study for water hammer happened by fluid phenomenon and corrosion rate by flow velocity. In this study, the corrosion test carried out using the ERW carbon steel pipe by changed the water speed and heat input in a month. The level of dissolved oxygen is maintained 5~5.5mg/l(amount of dissolved oxygen in tap water). The water speed for corrosion test is 1m/s, 2m/s, 3m/s. As the results, grooving corrosion rate is increased cause by water speed in the pipe. In the case of the ERW pipe with more heat input, grooving corrosion rate is decreased. It is therefore that welding heat input should be controlled based on the carbon content of the pipe in order to improve the corrosion reistance of the ERW pipe.

• Corrosion Science and Technology
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• v.12 no.4
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• pp.179-184
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• 2013

Pipe wall thinning caused by erosion and corrosion can adversely affect the operation of aged nuclear power plants. Some injured workers owing to pipe rupture has been reported and power reduction caused by unexpected pipe damage has been occurred consistently. Therefore, it is important to develop erosion-corrosion damage prediction model and investigate its mechanisms. Especially, liquid droplet impingement erosion(LDIE) is regarded as the main issue of pipe wall thinning management. To investigate LDIE mechanism with corrosion environment, we developed erosion-corrosion damage simulation apparatus and its capability has been verified through the preliminary damage experiment of 6061-Al alloy. The apparatus design has been based on ASTM standard test method, G73-10, that use high-speed rotator and enable to simulate water hammering and droplet impingement. The preliminary test results showed mass loss of 3.2% in conditions of peripheral speed of 110m/s, droplet size of 1mm-diameter, and accumulated time of 3 hours. In this study, the apparatus design revealed feasibility of LDIE damage simulation and provided possibility of accelerated erosion-corrosion damage test by controlling water chemistry.

• Journal of Mechanical Science and Technology
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• v.14 no.2
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• pp.152-158
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• 2000

The contents of this paper include the evaluation of corrosion characteristics and the behaviour of stress corrosion cracking (SCC) for the weldment and post weld heat treatment (PWHT) specimen and parent of HT -60 steel using a slow strain rate test (SSRT) in synthetic seawater. Corrosion characteristics were obtained from the polarization curves by potentiostat, and SCC phenomena were evaluated through the parameters such as reduction of area and time to failure by comparing the experimental results in corrosive environment with those obtained in air. Corrosion rate of the weldment was the fastest, followed by parent and PWHT specimen. SCC phenomena between the weldment of HT-60 steel and synthetic seawater were shown. Besides, SCC was dependent upon the pulling speed greatly. Maximum severity of SCC was obtained at a speed of $10^{-6}mm/min$, whereas SCC could not be seen almost at $10^{-4}mm/min$. The resistance to SCC for PWHT specimen was improved considerably compared that of the weldment at $10^{-6}mm/min$. In case of SCC failure, it was verified from SEM examination that brittle mode and lots of pits could be seen at the fractured region near the surface of the specimen.

• Journal of the Korean Chemical Society
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• v.55 no.4
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• pp.575-580
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• 2011

It was investigated into the effects on zinc corrosion of the rotation speed of Zn-RDE and the oxygen concentration in borate buffer solution. Zinc corrosion was heavily influenced on the rotation speed of electrode and the oxygen concentration. We have suggested the disproportion reaction following the reversible one electron transfer as the corrosion mechanism of zinc.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.1132-1140
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• 2007

As it recently appears that Life Cycle Cost Analysis may be considered as new methodology for economic valuation of infrastructure many researches have been made to assess LCC(Life Cycle Cost) of each facility based on a reasonable methods. In general, LCC is composed of construction cost and expected maintenance repair cost. And especially, maintenance repair cost must be estimated to enhance the reliability through systematic and reasonable methods. However in Korea, because high speed railway steel bridges are recently constructed no direct statistical data are available for the account of the maintenance cost and then their maintenance characteristics are not linear yet. Therefore, the approach proposed in the paper utilizes a theoretical determination and degradation of the corrosion and fatigue of the bridges based on Rahgozar et al.(2006)'s model on fatigue notch factor considering into the corrosion to incorporate the corrosion effect into the fatigue strength reduction model. And then, the corresponding probability of failure is calculated in terms of the reliability index using S-N curve to formulate the fatigue limit state. Therefore, this paper proposes the minimum Life Cycle Cost through optimum maintenance plan analysis of high-speed railway steel bridges under construction. Finally, this paper reviews the proposed model in oder to confirm the applicability and feasibility by appling it to high speed railway steel bridges under construction

• Journal of the Korean institute of surface engineering
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• v.30 no.1
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• pp.33-43
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• 1997

The effects of process parameters substrate such as substrate current and substrate temperature on the corrosion resistance of ion plated TiN film were investigated. TiN fims were deposited on speed steel on which Ti or Ni hed been previously evaporated. Dense TiN films could be obtained under higher substrate current(1A) and substrate temperature($500^{\circ}C$), whereas TiN films deposited with lower substances current(0.5A) and substrate temperature($300^{\circ}C$) showed porous structure. The corrosion resistances of high speed steel was considerably increased when dense TiN films had been formed on it. The effect of Ti and Ni interlayer on the increase of the corrosion resistance was also significant with dense TiN films, while there was little effect of interlayer on the corrosion resistance when TiN films were porous. the effect of interlayer on the corrosion resistance was more outstanding with Ti then with Ni, because Ti reacts more easily with oxygen to form an oxide layer, and it also shows higher resistance against chlorine containing corrosion media.