• Journal of the Korean Society for Heat Treatment
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• v.12 no.1
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• pp.9-20
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• 1999

The effect of post oxidation, water-quenched after holding in air for 5~420 seconds or cooling or furnace cooling, on corrosion resistance and phase formation characteristics of the surface layer of SM20C and SM45C carbon steels after gas nirtrocarbursing in the $NH_3-5%CO_2-N_2$ gas atmosphere at $580^{\circ}C$ for 3hours is studied. The compound layers of two steels consist of ${\varepsilon}-Fe_{2-3}N$, ${\gamma}^{\prime}-Fe_4N$ and $Fe_3O_4$, phases, however, the quantity of ${\gamma}^{\prime}-Fe_4N$ phase increases for the furnace cooled specimen compared to that of air cooling specimen. With increasing $NH_3$ content in the gas mixture and also increasing the keeping time in the air after gas nitrocarburising, the ${\varepsilon}-Fe_{2-3}N$ phase of compound layer increases, while the decreased current density recognizing the improvement of corrosion resistance are shown. the passive current density of SM45C steel is lower than that of SM20C steel at the same nitrocarburising conditions.

• Journal of the Korean Society of Safety
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• v.29 no.6
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• pp.87-93
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• 2014

In this study, the reinforced concrete rahmen bridge damaged by the chloride attack was investigated. According to the investigation, the degraded concretes on cantilever kerb and end part were intensively observed. Thus, the chloride content test and half-cell method were performed to evaluate the degraded parts. As a result, the contents of chloride on degraded parts were C and D grade. On the other hand, the half-cell potential values of rebar in degraded concrete were measured with the minor corrosion. This rebar corrosion is expected to progressing. Chloride content D grade is due to expansion pressure by corrosion of rebar and freeze-thaw by permeate water, could see progresses rapidly degradation. In order to prevent chloride attack to concrete deck caused by deicing salts, corresponding to the chloride critical concentration must maintain grade b or at least grade c. Chloride condition evaluation standard apply to evaluation of marine structure chloride attack with chloride attack by deicing salts.

• Corrosion Science and Technology
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• v.6 no.6
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• pp.269-274
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• 2007

The corrosion of steel in concrete is significant in marine environment. Salt damage is one of the most detrimental causes to concrete bridges and port structures. Especially, the splash and tidal zones around water line are comparatively important in terms of safety and life-time point of view. During the last several decades, cathodic protection (cp) has been commonly accepted as an effective technique for corrosion control in concrete structures. Zn-mesh sacrificial anode has been recently developed and started to apply to the bridge column cp in marine condition. The detailed parameters regarding Zn-mesh cp technique, however, have not well understood so far. This study is to investigate how much Zn-mesh cp influences along the concrete column at elevated temperature. About 100 cm column specimens with eight of 10 cm segment rebars have been used to measure the variation of cp potential with the distance from Zn-mesh anode at both $10^{\circ}C$ and $40^{\circ}C$ in natural seawater. The cp potential change and current diminishment along the column specimens have been discussed for the optimum design of cp by Zn-mesh sacrificial anode.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2010.05a
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• pp.77-81
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• 2010

This study deals with the analysis of color-difference and physical property of anti-corrosion coatings using at inside of concrete tank for drinking water. Because anti-corrosion coatings are effected by chemical attack, color and physical property are changed. So in this study when epoxy resin coatings of 3 types were received chemical attack by Cl- and NaOH, we present the co-relationship between color-difference and bond strength. For this study, we used the colorimetry, which can measure the degree of color difference on surface of materials. As the results, in case of Cl-, color change is appeared, bond strength also is decreased. From this experiment, we could know that color change due to chemical aging has the deep relationship with physical performance(bond strength) materials. further researches are needed.

• Journal of Surface Science and Engineering
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• v.47 no.3
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• pp.121-127
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• 2014

In this study, in order to improve corrosion resistance and wear resistance of aluminum, surface treatment was made by anodizing with oxalic acid solution and sealing with nano-diamond powder. Average size of nano-diamond powder was 30nm. Anodizing with oxalic acid made many pores in the aluminum oxide layer. Pore size and oxide thickness were investigated by scanning electron microscope (SEM). Pore size increased as temperature increased and voltage increased. It was possible to make oxide layer with pore diameter more than 50 nm. Oxide thickness increased as temperature and voltage and treatment time increased. Oxide layer with above $10{\mu}m$ thickness was made. Aluminum oxide layer with many pores was sealed by water with nano-diamond powder. Surface morphology was investigated by SEM. After sealing treatment with nano-diamond powder, corrosion resistance, wear resistance and hardness increased.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2014.11a
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• pp.45-45
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• 2014

The importance of magnesium alloys has significantly increased due to their low density, high strength/weight ratio, very good electromagnetic shielding features and good recyclability. However, unfortunately, Mg alloys are very susceptible to corrosion due to their high chemically activities (= -2.356 V vs. NHE at $25^{\circ}C$), hence, most commercial Mg alloys require corrosion protective coatings. Organic coating such as painting, powder coating and electrophoretic deposition of paint (E-paint) is typically used in the final stages of the coating process of Mg alloys. In this study, effect of pre-immersion time on the deposition of E-paint on AZ31 Mg alloy was investigated. It was found that during pre-immersion time, AZ31 Mg alloy rapidly reacts with E-paint solution and paint can be self-deposited on the AZ31 surface without applying of electric current. The pore size on the E-painted AZ31 Mg alloy increased with increasing pre-immersion time from 0 to 5 min. Both adhesion and corrosion resistance of E-painted AZ31 Mg alloy decreased with increasing pre-immersion time. The best E-paint AZ31 Mg alloy, which showed stronger adhesion after water immersion test and good corrosion resistance, was started to deposit after 5 s of pre-immersion time.

• Corrosion Science and Technology
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• v.7 no.5
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• pp.274-282
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• 2008

Ships' hull is typically protected by a combination of protective coating system and electrical cathodic protection system, which has been an economical and effective measure for ship's hull to date. However, ships' rudder and adjacent hull areas are known to be subjected to premature corrosion damages, which require more frequent coating repair than other hull areas. Conventional organic coating system for ship's hull has been known only to remain intact just for 2~3 months on the rudder and adjacent area, especially for the fast-going ships such as container carriers or naval vessels. In this study, special organic/inorganic coating materials, which are commercially available, were tested in terms of cavitation resistance as an alternative to existing rudder & hull protection system. Both standard ultrasonic tester and in-house developed ultra water jet test method were employed as a means to evaluate their performance against cavitation induced damages. Additionally, the overall cost evaluation and workability at actual shipyard were discussed.

• Corrosion Science and Technology
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• v.7 no.6
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• pp.307-314
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• 2008

The influence of a moist atmosphere on $90^{\circ}$ domain switching under a sustained electric field, stress corrosion cracking of an indentation crack in water and an aggressive solution, and the relation between penetrating crack propagation and domain switching were studied using $BaTiO_3$ single crystal. The results indicate that enlarging the domain switching zone and crack propagation could be facilitated by a moist atmosphere or an aggressive solution due to the indentation residual stress. A moist atmosphere exerts remarkable influence upon the polarization of $BaTiO_3$ single crystal under a sustained electric field, and the surface energy of the c domain was much lower than that of the a domain. Domain switching ahead of a penetrating indentation crack tip was an essential requirement for crack propagation under constant stress.

• Journal of Ocean Engineering and Technology
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• v.15 no.1
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• pp.57-66
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• 2001

In order to measure steel corrosion in mortar by a transient electro-magnetic (TEM) Method, the development of the sensors have been studied. The sensors were made of enamelled wire with diameter of 0.25mm and Acril. The sensor configuration was used as a coincident loop type. The secondary electro motive force(EMF) was measured with SIROTEM III. The accelerator was equipped with the SIROTEM III. The accelerator permits the transmitter to turn off approximately 10~15 times faster than normal. The high resolution time series used for very shallow or high resistivity investigation was selected. The steels were embedded in mortar which were made from sand : cement : water ratio of 2 : 1: 0.5. The mortar specimen was 50cm long, 20cm wide and 10cm thick. To investigate steel corrosion in mortar, the sensors used were with 2$\times$2$cm^2$(3, 6, 9$\Omega$), 3$\times$3$cm^2$(3, 6, 9$\Omega$) and 6$\times$6$cm^2$(3, 6, 9$\Omega$). The obtained result obtained showed that the sensor 8(6$\times$6$cm^2$, 6$\Omega$) was the proper sensor for the measurement of steel corrosion in mortar.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.11
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• pp.23-29
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• 2010

The principal factor determining an optimum design method for cathodic protection is finding the protection current for preventing the corrosion of existing, already laid pipe. Some factors currently used to test designs include the sizes and lengths of pipes, soil resistivity, and the coating damage rate. We believe this method and current formulae are not optimum due to the uncertainty of determining the coating damage rate and the corrosion protection current's density. This paper analyzes the amount of protection current obtained by performing a temporary current test using data describing existing laid pipe. We then propose determining the corrosion protection current by using the temporary current test after modifying the formula. In addition, we suggest a way to choose optimized cathodic protection and the process of design by executing the design and taking account of such factors as a site condition of 34km-long non-protected water supply pipe lines (stages I and II) in ${\bigcirc}{\bigcirc}$ region, climate, interferences, and durability.