• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.6
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• pp.155-162
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• 2012

When RC (Reinforced Concrete) structures are exposed to sea water, steel corrosion can occur and this leads a degradation of structural performance. Referring the electro-deposition system with sea water from the 1st step research, durability and structural performance are evaluated in coated steel and RC members containing it in the 2nd research. In the durability performance test, Half Cell Potential test is performed and the coated steel is evaluated to have the high resistance to corrosion, which shows only 35% of corrosion velocity in normal (bare) steel. In the structural performance test, tensile strength, adhesive strength, and flexural/shear in RC member are performed. For the electro-deposit coated steel, increasing ratios of 3.2% and 8.8% are evaluated in the test of tensile strength and adhesive strength, respectively. For the structural test in RC member, there is no big difference between RC members with coated and non-coated steel in ultimate load and failure pattern It is evaluated that the chemical compound with $CaCO_3$ and $Mg(OH)_2$ from electro-deposition causes slightly increased structural performance. The electro-deposit coated steel can be more widely applied after performance verification from several tests like fatigue, resistance to impact, and long term-submerging test.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.25 no.2
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• pp.87-104
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• 1989

Recently, with the tendency of more lightening, high-strength and high-speed in the marine industries such as marine structures, ships and chemical plants, the use of the aluminium Alloy is rapidly enlarge and there occurs much interest in the study of corrosion fatigue crack characteristics. In this paper, the initiation of surface crack and the propagation characteristics on the base metal and weld zone of 5086-H116 Aluminium Alloy Plate which is one of the Al-Mg serious alloy(A5000serious) used most when building the special vessels, were investigated by the plane bending corrosion fatigue under the environments of marine, air and applying cathodic protection. The effects of various specific resistances on the initiation, propagation behavior of corrosion fatigue crack and corrosion fatigue life in the base metal and heat affected zone were examined and its corrosion sensitivity was quantitatively obtained. The effects of corrosion on the crack depth in relation to the uniform surface crack length were also investigated. Also, the structural, mechanical and electro-chemical characteristics of the metal at the weld zone were inspected to verify the reasons of crack propagation behavior in the corrosion fatigue fracture. In addition, the effect of cathodic protection in the fracture surface of weld zone was examined fractographically by Scanning Electron Microscope(S.E.M.). The main results obtained are as follows; (1) The initial corrosion fatigue crack sensitibity under specific resistance of 25Ω.cm% show 2.22 in the base metal and 19.6 in the HEZ, and the sensitivity decreases as specific resistance increases (2) By removing reinforcement of weldment, the initiation and propagation of corrosion crack in the HAZ are delayed, and corrosion fatigue life increases. (3) As specific resistance decreases, the sensitivity difference of corrosion fatigue life in the base metal and HAZ is more susceptible than that of intial corrosion fatigue crack. (4) Experimental constant, m(Paris' rule) in the marine environment is in the range of about 3.69 to 4.26, and as specific resistance increases, thje magnitude of experimental constant, also increases and the effect by corrosion decreases. (5) Comparing surface crack length with crack depth, the crack depth toward the thickness of specimen in air is more deeply propagated than that in corrosion environment. (6) The propagation particulars of corrosion fatigue crack for HAZ under initial stress intensity factor range of $\Delta$k sub(li) =27.2kgf.mm super(-3/2) and stress ratio of R=0 shows the retardative phenomenon of crack propagation by the plastic deformation at crack tip. (7) Number of stress cycles to corrosion fatigue crack initiation of the base metal and the welding heat affected zone are delayed by the cathodic protection under the natural sea water. The cathodic protection effect for corrosion fatigue crack initiation is eminent when the protection potential is -1100 mV(SCE). (8) When the protection potential E=-1100 mV(SCE), the corrosion fatigue crack propagation of welding heat affected zone is more rapid than that of the case without protection, because of the microfissure caused by welding heat cycle.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2007.11a
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• pp.46-46
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• 2007

Zn, Al 및 Sn을 각각 도금한 강기판상에 Mg박막을 이온플레이팅법에 의해 제작하였다. 이와 같은 중간층을 가진 Mg막의 내식측정결과에 의하면, Mg과 갈바닉 전위차가 작은 Zn을 중간층으로 하여 제작한 Mg 막이 Fe 모재보다 낮은 자연 전위값을 안정적으로 유지하면서 희생양극적 방식효과를 장시간동안 나타내었다.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.11a
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• pp.194-195
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• 2005

(100-x)Zn xMg alloy films are prepared onto cold-rolled steel substrates; where x ranged from 0 to about 38 atomic %. The alloy films show microcrystalline and grain structures respectively, according to preparation conditions such as composition ratio of zinc and magnesium or gas pressures etc.. And X-ray diffraction analysis indicates not only the presence of Zn-Mg thin films with forced solid solution but also the one of $MgZn_2$ alloy films partly. In addition the influence of Mg/Zn composition ratio and morphology of the Zn-Mg alloy films on corrosion behavior is evaluated by electro-chemical anodic polarization tests in deaerated 3% NaCl solution. From this experimental results, all the prepared Zn-Mg alloy films showed obviously good corrosion resistance to compare with 99.99% Zn and 99.99% Mg Ingots for evaporation metal. It is thought that the Zn-Mg films with effective forced solid solution prepared by plasma enhanced PVD method, produces smaller and denser grain structure so that may improve the formation of homogeneous passive layer in corrosion environment.

• Journal of the Korean Society of Marine Environment & Safety
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• v.17 no.2
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• pp.155-160
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• 2011

In these days, there are increasing demands for weight reduction in many industrial fields including marine industries. Therefore, magnesium thin films for lightweight materials were prepared on magnesium alloy substrate. The influence of gas pressure and substrate bias voltages on the crystal orientation and morphology of the films was determined by using X-ray diffraction and FE-SEM, respectively. And the effect of crystal orientation and morphology of the magnesium thin films on corrosion behavior was estimated by measuring electro-chemical anodic polarization curves in deaerated 3% NaCl solution. From the results, corrosion resistance of Mg thin films was improved by controlling the crystal orientation and morphology of the films with effective use of plasma ion plating technique.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.6
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• pp.996-1003
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• 2001

In order to investigate the fatigue fracture characteristics by corrosion degradation of 12Cr alloy steel, both the fatigue characteristics in air of them artificially degraded during long period and the corrosion fatigue characteristics were experimentally evaluated in various environments which were determined from electro-chemical polarization tests. And also, their fracture mechanisms were analyzed and compared, fractographyically. From their results, the fracture mechanical characteristics of it artificially degraded during long period in the distilled water, 3.5 wt.% NaCl solution and 12.7wt.%(1M) Na$_2$SO$_4$solution of 25, 60 and 90$\^{C}$ did not show distinguishable difference comparing with non-corroded one in regardless of temperature and degradation period. It means that degradation of the material by just surface corrosion does not remarkably affect to fatigue crack growth. On the other hand, the crack growth rates by corrosion fatigue increased due to activity increase of corrosive factors such as OH(sub)-,Cl(sup)- and SO$_4$(sup)- at the crack tip with temperature increase. Therefore, the crack growth rates by corrosion fatigue were more faster than that in air of the artificially degraded specimen due to the such difference of crack growth mechanism.

• 유체기계공업학회:학술대회논문집
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• 2000.12a
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• pp.366-372
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• 2000

In a power plant, it is generally accepted that a turbine governor system is necessary to control amount of steam supply toward the turbine system. There are many kinds of trouble at this governor system, which is recognized one of the most sensitive systems in the power plant. Especially we have experienced the internal leakage of motorization oil of servo valve. In the study, we investigated the mechanism of an internal leakage such as erosion by foreign materials and corrosion by chemical reaction between chloric healed oil and motorization oil. A precautionary measures is also performed to help the field service engineers.

• Proceedings of the KIEE Conference
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• 2003.11a
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• pp.370-372
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• 2003

As there expands the usage of Al-Cu connections to interface aluminum and copper in power distribution systems, efforts to mitigate the mechanical, electrical or electro-chemical degradation are widely spreading. The explosive bending technology, in particular, has been thought as a countermeasure for the degradation. In this paper, electrochemical analysis and optical microscopic observation are carried out in order to compare the corrosion resistivities of the commercial compression type bimetallic sleeve and the explosion type bimetallic sleeve. The results show that the explosive bonding technology can prevent the interfacial corrosion caused by the formation of crevices and pits as well as from galvanic potential difference.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.109-110
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• 2006

We have studied the effect of C/Ti atomic ratio of TiCx (x=0.5, 0.75 and 1.0) raw powder on the properties of the Ti-Mo-WTiC sintered hard alloy. The decrease of C/Ti atomic ratio accelerated the densification in the sintering process. The hardness was remarkably improved up to 1350HV with decreasing the C/Ti atomic ratio because of increase of TiCx phase volume content and its fine dispersion. From the results of electro-chemical tests in acid and 3% NaCl solutions, it was obvious that every alloy had excellent corrosion resistance, which meant about 200 times better than that of WC-Co cemented carbide.

• Transactions of Materials Processing
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• v.18 no.8
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• pp.625-632
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• 2009

The influence of the subsequent-annealing(SA) temperature on the plasma electrolytic oxidation(PEO)-treated Mgbased alloy was investigated in terms of surface properties associated with hardness and corrosion. For this purpose, a series of the SA treatments were performed on the PEO-treated samples at four different temperatures, i.e., 100, 150, 200, and $250^{\circ}C$ for 10 hrs. When compared to the sample without SA, the samples annealed at temperatures higher than $200^{\circ}C$ showed a difference in surface morphology due to the volume expansion accompanied by the dehydration reaction where the part of $Mg(OH)_2$ changed into MgO, working as harder phase. From the results of nano-indentation tests, the applied loads of the samples were seen to increase with increasing SA temperatures. However, the electro-chemical and corrosion properties of the sample annealed at $150^{\circ}C$ were higher than those of the samples annealed at three temperatures.