• International Journal of Railway
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• v.4 no.4
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• pp.86-92
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• 2011

Chloride ion diffusion at the corner of rectangular-shaped concrete structures is presented. At the corner of rectangular-shaped concrete, chloride ion diffusion is in two-dimensional process. Chloride ions accumulate from two orthogonal directions, so that corrosion-free life of concrete structures is significantly reduced. A numerical procedure based on finite element method is used to solve the two-dimensional diffusion process. Orthotropic property of diffusion coefficient of concrete is considered and chloride ion profile obtained from numerical analysis is used to produce transformed diffusion coefficient. Comparisons of experimental data are also carried out to show the reliability of proposed numerical analysis. As a result of two-dimensional chloride diffusion, corrosion-free life of concrete structure for railway is estimated using probability of corrosion initiation. In addition, monographs that produces transformed diffusion coefficient and corrosion-free life of concrete structure are made for maintenance purpose.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.11a
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• pp.109-110
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• 2021

An attempt has been made on a constructive approach to evaluate the performance of snail shell ash (SSA) for its corrosion performance under marine environments. Corrosion performance of steel rebar in chloride contaminated SSA with (0% to 50%) replacement levels of cement extract medium was examined through electrochemical and weight loss techniques. Initially, snail shell powder (SSP) is made by pulverizing and subsequently SSA is by thermal decomposition methods. A critical level of 20 % SSA improved both corrosion resistance properties of cement extracts. SSA is a suitable replacement material for natural limestone in cement productions.

• Journal of Welding and Joining
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• v.18 no.5
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• pp.70-76
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• 2000

The effect of Post Weld Heat Treatment(PWHT) of RE36 steel for marine structure was investigated with parameters such as micro-vickers hardness, corrosion potential and corrosion current density of weld metal(WM), base metal(BM) and heat affected zone(HAZ), and both Al alloy anode generating current and Al alloy anode weight loss quantity etc. Hardness of post-weld heat treated BM, WM and HAZ is lower than that of As-welded condition of each region. However, hardness of HAZ was the highest among those three parts regardless of PWHT temperature and corrosion potential of WM was the highest among those three parts without regard to temperature and corrosion potential of WM was the highest among those three parts without regard to PWHT temperature. The amplitude of corrosion potential difference of each other three parts at PWHT temperature $550^{\circ}C$, $650^{\circ}C$ are smaller than that of three parts by As-welded condition and corrosion current density obtained by PWHT was also smaller than that of As-welded condition. Eventually, it was known that corrosion resistance was increased by PWHT. However both Al anode generating current and anode weight loss quantity were also decreased by PWHT compare to As-welded condition when RE36 steel is cathodically protected by Al anode. Therefore, it is suggested that the optimum PWHT temperature with increasing corrosion resistance and cathodic protection effect is $550^{\circ}C$.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.7 s.238
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• pp.930-937
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• 2005

One of the useful technology for light-weightening of components required in the automobile and machine industry is to use of high strength materials. To improve material properties, carbonizing treatment, nitrifying treatment, and shot-peening method are representatively applied, However, the shot-peening method is generally used to remove the surface defect of steel and to improve the fatigue strength on surface. Benefits by shot peening are to make increase resistance against fatigue, stress corrosion cracking, fretting, galling, erosion and closing of pores. In this paper, investigated the effect of shot peening on the corrosion of SUP-9 steel immersed in $3.5\%$ NaCl solution and corrosion characteristics by the heat treatment during shot peening process. The immersion test was performed on the four kinds of specimens. Corrosion potential, polarization curve, residual stress and etc. were investigated from the experimental results.

• Journal of Welding and Joining
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• v.18 no.6
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• pp.48-54
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• 2000

The corrosion properties of Ni-Cr-W-Mo-B alloy sprayed by the high velocity oxy-fuel spraying (HVOF) was studied as a function of heat treatment by using both potentiodynamic polarization and immersion tests in the H₂SO₄ solution. The mechanical property was also evaluated by a microhardness tester. Microstructural characteristics of te as-sprayed and annealed coatings at 550, 750 and 950℃ have been analyzed by means of OM, XRD, SEM and TEM. The results showed that the corrosion resistance was improved by increasing the annealing temperature. As-sprayed coating had metastable and heterogeneous phases such as amorphous, nanocrystalline and very refined grain and precipitates, which induced a localized corrosion. The localized corrosion occurred preferentially at the unmelted particles which were composed of Ni matrix and Cr, W and Mo riched phase segregated in the boundaries. As annealing temperature was increased, the microstructure had shown some changes - reduction of porosity and s[plat boundary decomposition and crystallization of amorphous/nanocrystalline phases, grain coarsening,, formation and growth of precipitates such as {TEX}$M_{23}C_{6}${/TEX} and {TEX}$M_{7}C_{3}${/TEX}. In addition, the compositional difference between matrix and boundary phases gradually disappeared, which changed the corrosion type from localized corrosion to general corrosion and thus enhanced corrosion resistance.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.4
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• pp.460-469
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• 2000

A study on the corrosion behavior of RE36 steel for marine structure was investigated with parameters such as micro-Vickers hardness, corrosion potential and corrosion current density measurement of weld metal(WM), base metal (BM) and heat affected zone(HAZ), Al anode generating current and Al anode weight loss quantity in case of cathodic protection. And we carried out slow strain rate test(SSRT) in order to research mechanical properties such as stress at maximum load, percent strain, time to fracture and strain to failure ratio etc and to find out limiting cathodic polarization potential for hydrogen embrittlement with applied cathodic polarization potential. Hardness of HAZ part was the highest among those three parts and also galvanic corrosion susceptibility was the highest in HAZ part among those three parts due to the lowest corrosion potential than other parts. However corrosion current density was the highest in WM part among those three parts. And the optimum cathodic polarization potential showing the best mechanical properties obtained by SSRT method with applied constant cathodic potential was from - 770mV to - 875mV(SCE). However it is suggested that limiting cathodic polarization potential indicating hydrogen embrittlement on the mechanical properties was under - 900mV(SCE).

• Journal of the Korea Institute of Building Construction
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• v.14 no.6
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• pp.505-513
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• 2014

The purpose of this study is to evaluate the corrosion protective properties of a Zn-Sn metal spray method according to the contents of Zn and Sn by a CASS test and the electrochemical theory. In the experiment, the CASS test and the electrochemical test were conducted to investigate the corrosion protective property of the Zn-Sn Metal Spray system, the Zinc galvanizing system, and the heavy duty coating system. As a result, it was confirmed that the Zn-Sn (65:35) Metal Spray system had very high corrosion protective property through the electrochemical characteristic as comparison with the other anti-corrosion systems and was very effective to prevent steel products from corrosion.

• Proceedings of KOSOMES biannual meeting
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• 2005.05a
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• pp.161-165
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• 2005

Recently, it is on the increase interest for Al alloy with new material for ship application to substitute for FRP ship. The reason is thatAl alloy ship has beneficial characteristics such as high sea speed, increase of loadage and easy to recycle compared with FRP ship. In this paper, mechanical and electrochemical properties are investigated by slow strain rate test experiment in various applied potential condition. These results will provide as reference data to design ship by deciding optimum protection potential regard to hydrogen embrittlement and stress corrosion cracking. In general, Al and Al alloys are not corroded with forming film which has the corrosion resistance property in neutral solution. However, it was observed that formation and destruction of passive film by $Cl^-$ ion in sea water environment. At comparison of current density after 1200 sec in potentiostatic experiment, the current density in the potential range of -0.68 $\~$-1.5 V is shown low value. The low current density means protection potential range. Elongation in applied potential of 0 V was high. However, the corrosion protection application in this condition is impossible potential because the toughness is low value by decreasing strength by active dissolution reaction at parallel part of specimen. The film composed with $CaCO_3$ and $Mg(OH)_2$ has a corrosion resistance property. However, the uniform electrodeposition coating at below -1.6 V potential is not formed since the time to form the uniform electrodeposition coating is short. Therefore, it is concluded that mechanical property is poor because effect by hydrogen gas generation is larger than that of electrodeposition coating. It is concluded that the optimum protection potential range from comparison of_maxim urn tensile strength, elongation and time to fracture is -1.3$\~$0.7 V (SSCE).

• Journal of Korea Foundry Society
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• v.35 no.3
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• pp.45-52
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• 2015

The effect of different C and Cr/Mo contents, which were varied within the range allowed in the relevant specification, on the mechanical and corrosion properties of A487 alloy cast steel were examined. The increase in strength level with increasing C content and the decrease in strength along with the increase in tensile elongation with decreasing Cr/Mo contents were observed in A487 alloys with different C and Cr/Mo contents. At room temperature, the decrease in Cr/Mo content was beneficial in improving the impact properties of A487 alloy, with no notable difference in absorbed energy with varying C content. The impact properties of A487 alloy at $-60^{\circ}C$, on the other hand, greatly improved with the increase in C and the decrease in Cr/Mo contents. The corrosion behavior of A487 alloys in 3.5% NaCl solution did not show any meaningful change with different C and Cr/Mo contents.

• Proceedings of the Materials Research Society of Korea Conference
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• 2006.05a
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• pp.36.2-36.2
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• 2006