• Journal of Welding and Joining
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• v.11 no.2
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• pp.42-52
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• 1993

The corrosion fatigue fracture behaviour of dual phase steel was investigated in 3% NaCl solution at 302MPa and 137MPa. Fatigue test was conducted by cantilever type of self-made rotary bending fatigue testing machine. The fatigue strength increased with increasing the hardness of 2nd phase. Corrosion pit originated at the boundary of the 2nd phase. The size and number of corrosion pits were influenced by the 2nd phase hardness, and pits remained constant in size just after they were transited into cracks. The life of crack initiation was effected by stress level. The shape of relation of .DELTA. K and da/dN has smaller scattering in it in 3% NaCl solution than that in air. The higher the 2nd phase hardness is, the greater the corrosion fatigue life becomes. Corrosion fatigue fracture behaviour was primarily effected by mechanical factor in case of high stress(302MPa), but by electro-chemical reaction in a lower stress(137MPa). As stress level got lower and hardness of the 2nd phase got higher, the roughness of fracture surface increased.

• Corrosion Science and Technology
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• v.7 no.6
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• pp.328-331
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• 2008

Corrosion behaviour of water intake gate steel structures with different protective measures was investigated. Five material alternatives were taken for investigation, including: imported and recycled stainless steel, carbon steel with hot zinc spraying, painting and composite coatings. Results of corrosion rate for carbon steel, SUS 304, hot zinc spray coats in three water systems of Mekong river basin (saline, blackish and fresh) were also presented. Corrosion rate of carbon steel decreased with decreasing salinity in the investigated water environments. Meanwhile, these values for zinc coated steel, behaved by another way. Environmental data for these systems were filed and discussed in relation with corrosion characteristics. Method of Life Cycle Assessment (LCA) was applied in materials selection for water intake gate construction. From point of Life Cycle Cost (LCA) the following ranking was obtained: Zinc sprayed steel < Recycled stainless steel < Composite coated steel < Painting steel < SUS 304 From investigated results, hot zinc spray coating has been applied as protective measure for steel structures of water intake systems in Mekong river basin.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.686-691
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• 2004

The present paper describes an experimental study on the corrosive behaviour of Rolling stock structures. It is important to predict corrosive behaviour of rolling stock structures for safe service and to know relation between corrosion and fatigue life. This paper practiced electrochemical corrosion test of SS400 and SM490A. This study will examine the corrosive properties and differences of SS400 and SM490A from measuring corrosion potential, corrosion current density and corrosion rate.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.10a
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• pp.207-212
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• 1996

Recently, massive concrete structures exposed to salt from ocean marine environments, or from winter deicing. The corrosion caused by chloride-penetration may affect severey the durability and service life of such a concretestructures. Thus, it is necessary to develop durable concrete to enhance the corrosion resistance. In this study, we investigate the usage of adequate corrosion-protection materials in order to reduce permability-coefficient of concrete and method of enhancing the durability of concrete structures using by penetrating corrosion-protection materials.

• KIEAE Journal
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• v.10 no.3
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• pp.103-110
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• 2010

Carbonation is one of the major deterioration factors for concrete. So. lots of researchers have proposed the equations for determining carbonated depth and the initial time of steel corrosion due to carbonation to predict the service life of concrete structures. However, there are large gaps among the equations for predicting carbonation because each researcher has different considering factors to predict carbonation depth. So, in this study, we calculated the deviations of the proposed equations for carbonation, and we calculated each researcher different corrosion initiation time. However, it has a lot of deviation. Therefore, we evaluated the probability of steel corrosion considering each deviation using MCS, an analysis method based on probability theory. In the results, we have proposed much advanced information for determining service life of reinforced concrete structures due to carbonation.

• Corrosion Science and Technology
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• v.2 no.5
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• pp.247-251
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• 2003

The corrosion forms of automotive body panels are various. One of the representations is a corrosion pitting and its propagation on the lapped portion by galvanic corrosion. But it has been difficult in correlation analysis about the corrosion propagation rate and mechanism of pitting and the actual automotive body in field. This present study interprets experimentally the rust pitting occurrence mechanism on the lapped panels through experimental methods. And field car investigation was executed for correlation analysis with experimental results. This paper compares corrosion propagation rate by pitting on hot-dip galvannealed steel sheets with corrosion forms in the automotive field condition. The research fundamentals which make it possible to predict the pitting occurrence and propagation on the lapped panels in the actual vehicles are given.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1A
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• pp.75-89
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• 2006

This paper presents a practical and realistic Life-Cycle Cost (LCC) optimum design methodology of steel bridges considering time effect of bridge reliability under environmental stressors such as corrosion and heavy truck traffics. The LCC functions considered in the LCC optimization consist of initial cost, expected life-cycle maintenance cost and expected life-cycle rehabilitation costs including repair/replacement costs, loss of contents or fatality and injury losses, road user costs, and indirect socio-economic losses. For the assessment of the life-cycle rehabilitation costs, the annual probability of failure which depends upon the prior and updated load and resistance histories should be accounted for. For the purpose, Nowak live load model and a modified corrosion propagation model considering corrosion initiation, corrosion rate, and repainting effect are adopted in this study. The proposed methodology is applied to the LCC optimum design problem of an actual steel box girder bridge with 3 continuous spans (40 m+50 m+40 m=130 m), and various sensitivity analyses of types of steel, local corrosion environments, average daily traffic volume, and discount rates are performed to investigate the effects of various design parameters and conditions on the LCC-effectiveness. From the numerical investigation, it has been observed that local corrosion environments and the number of truck traffics significantly influence the LCC-effective optimum design of steel bridges, and thus realized that these conditions should be considered as crucial parameters for the optimum LCC-effective design.

• 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 Ocean Engineering and Technology
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• v.14 no.2
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• pp.106-111
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• 2000

Recently it was reported that the life of Al Sacrifical anode is being used in port piers has been significantly shortened compared with the original design life (e.g. average life shortened from 20 years to 13-15 year) Those factors involving these problems mentioned above were seemed to be a quality of anode material and diverse environmental factors such as pH flow rate temperature Dissolved oxygen Chemical oxygen demand and resistivity etcm In this study flow rate and contamination degree(pH) of sea water affecting to sacrificial anode life hve been investigated in terms of electrochemical characteristics of Al alloy sacrificial anode It was known that the lifetime of Al alloy anode was shortened not only by increasing of self-corrosion quantity by varying flow rate of sea water but also by increasing corrosion current density due to the potential difference increment between Al anode and steel structure cathode by varying contamination degree of sea water. Especially when anode current density is from 1mA/cm2 to 3mA/cm2 and flow rate of sea water is under 2m/s anode current efficiency is 90% above However flow rate is over 2m/s anode current efficiency fell down sharply due to erosion corrosion as well as galvanic corrosion.

• Corrosion Science and Technology
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• v.16 no.4
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• pp.167-174
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• 2017

Bicarbonate/carbonate and molybdate anions have been characterized for their inhibitive effect on pitting corrosion of carbon steel in simulated concrete pore solution by using electrochemical tests such as electrochemical impedance (EIS) and linear polarization (LP). It was revealed that bicarbonate/carbonate has a weak inhibitive effect on pitting corrosion that is approximately one order of magnitude lower compared to hydroxide. Molybdate is effective against pitting corrosion induced by the concentration of chloride as low as 113 mM and can increase the pitting potential of a previously pitted sample to the oxygen evolution potential by the concentration of molybdate as much as 14.6 mM only. The formation of a $CaMoO_4$ film on the surface hinders the reduction of dissolved oxygen on the steel surface, reducing corrosion potential and increasing the safety margin between corrosion potential and pitting potential further. In addition, pore-plugging by $FeMoO_4$ as a type of salt film within pits increases the likelihood of repassivation.