• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.28 no.1
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• pp.61-70
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• 1992

In this study, corrosion fatigue test of SAPH45 steel was performed by the use of plane bending fatigue tester in marine environment and investigated fracture surface growth behavior of base metal and heat affected zone corrosion fatigue. The main results obtained are as follows: 1) Fracture surface growth of heat affected zone (HAZ) is delayed more than that of base matel (BM), and they tend to faster in seawater than in air. 2) Corrosion sensitivity to corrosion fatigue life of HAZ is more susceptible than that of BM. 3)In the case of the corner crack by corrosion fatigue, the correlation between the propagation rate of fracture surface area(dA/dN) and stress intensity factor range(ΔK) for SAPH45 are applied to Paris rule as follows: dA/dN=C(ΔK) super(m) where m is the slope of the correlation, and is about 6.60-6.95 in air and about 6.33-6.41 in seawater respectively.

• Journal of Korea Foundry Society
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• v.36 no.4
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• pp.117-125
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• 2016

The effects of the Zn content on the microstructure and corrosion behavior in 1M NaCl solution were investigated in Mg-(0~6)%Zn casting alloys. The MgZn phase was scarcely observed in the Mg-1%Zn alloy, while the Mg-(2~6)%Zn alloy consisted of ${\alpha}$-(Mg) and MgZn phases. With an increase in the Zn content, the amount of the MgZn phase was gradually increased. Immersion and electrochemical corrosion tests indicated that the Mg-1%Zn alloy had the lowest corrosion rate among the alloys, and a further increase in the Zn content resulted in the deterioration of the corrosion resistance. Microstructural examinations of the corroded surfaces and EIS analyses of surface corrosion films revealed that the best corrosion resistance at 1%Zn was associated with the absence of MgZn phase particles in the microstructure and the contribution of Zn element to the formation of a protective film on the surface. A micro-galvanic effect by the MgZn particles led to the increased rate of corrosion at a higher Zn content.

• Journal of Korea Foundry Society
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• v.34 no.6
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• pp.187-193
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• 2014

In the present work, the effect of adding Ce on the corrosion behavior of Mg-4Al-2Sn-1Ca alloy was investigated. The studied alloys were fabricated by gravity casting method and a potentiodynamic polarization, A.C. impedance and hydrogen evolution tests were carried out in a 3.5% NaCl solution with pH 7.2 at room temperature to measure the corrosion properties of Mg-4Al-2Sn-1Ca-xCe alloys. The microstructure of the Mg-4Al-2Sn-1Ca alloy was composed of ${\alpha}$-Mg, Mg17Al12, Mg2Sn and CaMgSn phase. Also, a $Al_{11}Ce_3$ phase was newly formed by the addition of Ce. With an increase of the Ce contents, the microstructure became refined and the corrosion resistance improved.

• Journal of Korea Foundry Society
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• v.33 no.3
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• pp.127-133
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• 2013

The influences of a small amount of CaO addition on the microstructure and corrosion behavior of AZ81 casting alloy have been investigated by means of optical microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, immersion and electrochemical tests. The added CaO led to the refinement of ${\alpha}$-Mg grains and the decrease in ${\beta}$ precipitate content by the formation of an $Al_2Ca$ phase. The AZ81-CaO alloy had a better corrosion resistance than the AZ81 alloy. The microstructural characterization on the corroded surface revealed that the enhanced corrosion resistance of the CaO-containing alloy may well be ascribed to the increased barrier effect of precipitates formed more continuously along the grain boundaries and the incorporation of Al and Ca elements into the corrosion film, by which it became more protective.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.7 s.178
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• pp.1841-1846
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• 2000

To examine the effect of acid fog on the corrosion fatigue behavior in structural steel, fatigue tests under acid fog atmosphere were carried out in comparison with distilled water. The corrosive c omponents contained in acid fog pile up the corrosion products on crack face and show a crack branching and crack tip blunting. Therefore, due to these workings crack growth rate was reduced by decreasing the effective stress range in crack tip rather than under distilled water. Also the effect of sulfuric acid, which is the main component of acid fog, and testing speed on fatigue crack growth were examined. It was found that corrosion behavior was remarkably dependent upon pH and Hz rather than components of acid fog. According as pH and testing speed decrease below a specific value, crack growth was accelerated in comparison with distilled water. This reveals that due to liquid having strong acidity and slow speed of test the crack face dissolution was promoted, so crack closure was disturbed in the process of stress descent.

• Korean Journal of Materials Research
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• v.27 no.10
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• pp.552-556
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• 2017

Evaluation of the durability and stability of materials used in power plants is of great importance because parts or components for turbines, heat exchangers and compressors are often exposed to extreme environments such as high temperature and pressure. In this work, high-temperature corrosion behavior of 316 L stainless steel in a carbon dioxide environment was studied to examine the applicability of a material for a supercritical carbon dioxide Brayton cycle as the next generation power plant system. The specimens were exposed in a high-purity carbon dioxide environment at temperatures ranging from 500 to $800^{\circ}C$ during 1000 hours. The features of the corroded products were examined by optical microscope and scanning electron microscope, and the chemical compound was determined by x-ray photoelectron spectroscopy. The results show that while the 316 L stainless steel had good corrosion resistance in the range of $500-700^{\circ}C$ in the carbon dioxide environment, the corrosion resistance at $800^{\circ}C$ was very poor due to chipping the corroded products off, which resulted in a considerable loss in weight.

• Journal of the Korean Society for Heat Treatment
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• v.28 no.4
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• pp.190-199
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• 2015

The study is intended to investigate the effect of solution treatment on microstructure and corrosion behavior of AZ91(Mg-9%Al-1%Zn-0.3%Mn)-2%Ca casting alloy. In as-cast state, the AZ91-2%Ca alloy consisted of intermetallic ${\beta}(Mg_{17}Al_{12})$, $Al_8Mn_5$ and $Al_2Ca$ phases in ${\alpha}-(Mg)$ matrix. After the solution treatment, Al within the ${\alpha}-(Mg)$ matrix was distributed more homogeneously, along with the slight decrease in the total amount of intermetallic compounds. The corrosion resistance of the AZ91-2%Ca alloy was improved after the solution treatment. The microstructural examinations for the solution-treated samples revealed that the better corrosion resistance may well be related to the incorporation of more oxides and hydroxides such as $Al_2O_3$, $Al(OH)_3$, CaO and $Ca(OH)_2$ into the surface corrosion product without dissolution of the intermetallic phases along the grain boundaries.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.33 no.3
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• pp.202-208
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• 1997

The component materials threatened by cavitation include ship propellers as well as turbine runners, pump impellers, pipe lines and radiators. Today it is known that cavitation damage takes place on many other components including on the coding water side of the cylinder liners of diesel engines. Cavitation erosion - corrosion implies damage to materials due to the shock pressure or shock wave that results when bubbles form and collapse at a metal surface within a liquid. To suppress cavitation erosion as well as cavitation erosion - corrosion to hydraulic equipment, innovations such as the improvement in the geometric design of the equipment or the selection of suitably resistant construction materials are necessary. In this study, we investigated that the cavitation erosion - corrosion damage under vibratory cavitation can be reduced by adding of side now velocity to the cavitation bubble group in order to eliminate bubbles formed in sea water environment.

• Journal of Korean Society of Steel Construction
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• v.16 no.5 s.72
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• pp.621-628
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• 2004

This paper introduces a new theory, that in a stiffened plate, a steel stiffener could be substituted a composite material in order to prevent from buckling. Changing a steel stiffener into a composite material would not only preclude welding, but could also prevent damage to the material due to fatigue and corrosion.A composite material is assumed to adhere to a steel plate, and is never separated from the plate until the steel plate reaches buckling.Such plate has variable shapes, with different lengths and widths, and also shows an anisotropic material property. LUSAS, a commercial finite element analysis package, was used in the buckling analysis.This paper investigated buckling behavior in anisotropic composite plates with variable parameters.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2015.11a
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• pp.351-351
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• 2015

음극방식법은 피방식체에 외부전원을 인가하거나 보다 활성 금속을 전기적으로 연결하여 피방식체를 일정 전위까지 음극분극 되도록 하여 부식을 억제하는 방법이다. 해수 중 음극방식을 실시할 경우 생성되는 석회질 피막(Calcareous deposit)은 소요전류밀도 감소로 인한 희생양극의 수명연장 및 물리적 방호벽 역할을 한다. 그러나 일반적인 석회질 피막은 세라믹과 같은 화합물로써 밀착력이 매우 약하며, 적지 않은 피막 형성 시간이 소요된다. 따라서 본 연구에서는 해수 중 음극전류 프로세스를 응용하여 실제 강관의 해중부 및 간만대 영역까지 석회질 피막을 균일-치밀하게 형성시키기 위한 최적의 조건을 찾고자 하였다. 각 조건별로 제작된 석회질 피막은 SEM, EDS 및 XRD를 통해 막의 모폴로지, 조성원소 및 결정 구조를 분석하였으며, 이를 바탕으로 희생양극 종류(Al, Zn) 및 1, 3, $5mA/m^2$의 전류밀도 조건에서 부위-기간별 형성된 석회질 피막의 메커니즘을 해명하였다. 또한 밀착성과 내식특성을 평가하기 위해 테이핑 테스트, 침지-자연전위 거동을 분석 및 평가하였다.