• Journal of Ocean Engineering and Technology
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• v.11 no.2
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• pp.28-38
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• 1997

The corrosion fatigue test was conducted in air to investigate the corrosion fatigue strength of SM 30 C steel by which was corroded in the under sea and surface in the conditions of 3.0% NaCl salt solution. The fatigue tests were carried out on a rotary bending testing machine of cantilever type. The corrosion effect of the sea surface conditionwas served more than that of the under sea condition which was due ti the periodic contact of air thus accelerate the corrosion. The difference of the fatgue strength between sea surface and under sea conditions decreased with increase of stree level and corroded period. Inthe case of the solid shaft and thickness 2mm of hollow shaft, the difference of corrosion fatigue strength decreased as stress level and corrosion periodic increasing. Onthe contrary in the case of thickness 1mm of hollow sgaft, the difference of it increased as stress level, corrosionn periooodic increasing and also the condition of corrosion chaanged. The main factors affecting the degradation of fatigue strength due to corrosion were the reduction of sectional area and the increase of surface roughness. The interference phenomenon increase with stress level got higher.

• Tribology and Lubricants
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• v.15 no.4
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• pp.335-342
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• 1999

Corrosion of the disk has been an ongoing concern for the manufacturers of hard disk drives. With the advent of magnetoresistive (MR) head, very low levels of corrosion and contamination become more critical since the raised defects and corrosion products on the disk surface-anything that heats the MR sensor due to the contact-can distort the output signal of the head. This phenomenon is called as thermal asperity. In this paper, the effect of corrosion as a form of Co migration on the occurrence of thermal asperity in MR drives was investigated. The corrosion test at high temperature (60$^{\circ}C$) and high relative humidity (80%) was emphasized in this study and the testing results at ambient condition were compared. The corrosion on the disks was characterized as the amount of Co ion migration using an ion chromatography (IC) and a time-of-flight secondary ion mass spectroscopy (TOF-SIMS). It is proved that corrosion on the disk surface after storage testing is closely correlated to the amount of Co ions migration from the magnetic layer to disk surfaces and higher Co migration causes more thermal asperities in the drive. In order to reduce Co migration, several methods such as burnishing process and structure of the carbon overcoat were investigated. It is found that the hydrogenated carbon overcoat shows the least Co migration among different types of overcoat layer. However, the most effective way to reduce Co migration is the application of Cr layer between the overcoat and the magnetic alloy layer.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.36 no.2
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• pp.132-138
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• 2000

The effect of fluid flow on corrosion and erosion-corrosion of metal is a well-recognized phenomenon in pipelines and machinery equipment, and so on. Not only are fluid hydrodynamics important, but also the corrosiveness of the process or production stream affects the corrosion system. Recent research demonstrates that it is possible to erosion-corrosion(E/C) phenomena in terms of hydrodynamics, electrochemical corrosion kinetics and film growth/removal phenomena. Stress corrosion cracking behavior under cavitation erosion-corrosion of mild steel(SS41) was investigated of base metal and weldment under loaded stress. Main result obtained are as follows : 1) The cavitation erosion sensitivity of base metal affected weight loss is more susceptive than heat affected zone, 2) The corrosion sensitivity affected weight loss of welding heat cycle is less susceptive on stress corrosion under cavitation erosion-corrosion than stress corrosion.

• Korean Journal of Materials Research
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• v.17 no.1
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• pp.43-49
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• 2007

Electrochemical migration phenomenon is correlated with ionization of anode electrode, and ionization of anode metal has similar mechanism with corrosion phenomenon. In this work, in-situ water drop test and evaluation of corrosion characteristics for SnPb solder alloys in $Na_2SO_4$ solutions were carried out to understand the fundamental electrochemical migration characteristics and to correlate each other. It was revealed that electrochemical migration behavior of SnPb solder alloys was closely related to the corrosion characteristics, and Sn Ivas primarily ionized in ${SO_4}{^2-}$ solutions. The quality of passive film formed at film surface seems to be critical not only for corrosion resistance but also for electrochemical migration resistance of solder alloys.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.05a
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• pp.7-8
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• 2017

Corrosion of reinforced concrete embedded in concrete is a deterioration phenomenon due to intrusion of embodied or Airborne chloride ions. Corrosion of a embedded steel increases the volume of the rebar and causes damage to the structure such as cracking and peeling of the concrete. This causes penetration of various corrosive factors and accelerates the corrosion of reinforcing bars, which has a serious effect on the durability of the structure. Researches on the corrosion phenomenon of these rebars by electrochemical methods have been carried out for a long time, but it is a lack of research in Korea. Therefore, in this study, one of electrochemical experimental methods, Tafel extrapolation method, was used to evaluate the performance of reinforcing bars according to the amount of NaCl and LiNO₂ added to concrete.

• Journal of Welding and Joining
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• v.26 no.4
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• pp.85-91
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• 2008

The grooving corrosion is caused mainly by the different microstructures between the matrix and weld which is formed during the rapid heating and cooling cycle in welding. By this localized corrosion reaction of pipes, it evolves economic problems such as the early damage of industrial facilities and pipe lines of apartment, and water pollution. So lots of researches were carried out already about grooving corrosion mechanism of ERW carbon steel pipe but there is seldom study for water hammer happened by fluid phenomenon and corrosion rate by flow velocity. In this study, the analysis based on hydrodynamic and fracture mechanics was carried out. ANSYS, FLUENT and STAR-CD were used for confirmation of flow phenomenon and stress on the pipe. As the results, fatigue failure is able to be happened by water hammer and grooving corrosion rate is increased cause by turbulent. Grooving corrosion is happened on the pipe, then friction loss of fluid is occurred from corroded part. Erosion can be happened enough in corroded region of microscopic size that wear "V" form. Also pipe is able to be damaged by water hammer effects because of corroded region is general acting as a notch effects. Corrosion depth was more than half of total thickness, it can be damaged from water hammer pressure.

• Corrosion Science and Technology
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• v.8 no.6
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• pp.232-237
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• 2009

Copper tubes are widely used in the distribution systems of drinking water throughout the world because of their excellent corrosion resistance, high thermal conductivity, and ease of fabrication. However, corrosion problems from copper tubes as blue water phenomenon and leakage have been reported appreciably. The effect of pH on the corrosion behavior of copper tube for tap water was investigated by electrochemical voltammetric techniques in synthetic tap water. And the copper corrosion cases were discussed from the viewpoint of factors affecting the corrosion rate such as pH, alkalinity, LSI(Langelier Saturation Index), and concentration of bicarbonate and dissolved carbon dioxide.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.3
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• pp.203-207
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• 1998

After etching Al-Cu alloy films using $SiCl_4/Cl_2/He/CHF_3$ plasma, a corrosion phenomenon on the metal surface has been studied with XPS (X-ray photoelectron spectroscopy) and SEM (Scanning electron microscopy). In Al-Cu alloy system, the corrosion occurs rapidly on the etched surface by residual chlorine atoms. To prevent the corrosion, the $SF_6$ plasma treatment subsequent to the etch has been carried out. A passivation layer is formed by fluorine-related compounds on etched Al-Cu alloy surface after $SF_6$ treatment, and the layer suppresses effectively the corrosion on the surface as the RF power of $SF_6$ treatment increases. The corrosion could be suppressed successfully with $SF_6$ treatment in the RF power of 150watts.

• Corrosion Science and Technology
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• v.9 no.6
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• pp.281-288
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• 2010

This study examined the carbon corrosion at Pt/C interface in proton exchange membrane fuel cell environment. The Pt nano particles were electrodeposited on carbon substrate, and then the corrosion behavior of the carbon electrode was examined. The carbon electrodes with Pt nano electrodeposits exhibited the higher oxidation rate and lower oxidation overpotential compared with that of the electrode without Pt. This phenomenon was more active at $75^{\circ}C$ than $25^{\circ}C$. In addition, the current transients and the corresponding power spectral density (PSD) of the carbon electrodes with Pt nano electrodeposits were much higher than those of the electrode without Pt. The carbon corrosion at Pt/C interface was highly accelerated by Pt nano electrodeposits. Furthermore, the polarization and power density curves of PEMFC showed degradation in the performance due to a deterioration of cathode catalyst material and Pt dissolution.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.30 no.4
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• pp.312-319
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• 1994

Recently, with the rapid development in the industries such as an iron mill and chemical plants, there is enlarged by the use of the piping. Sepecially, the piping connected with a fluid, if it is increase the speed of running fluid, ought to generate cavitation phenomenon with unbalanced pressure. So, the cavitation phenomenon cause serious damage of the piping, because it generate erosion and corrosion in the piping. In this study, the steel pipe piping water (SPPW) and SPPW on weldment were tested by using of cavitation-erosion test apparatus with nozzle and were investigated under the marine environment of liquid. (specific resistance : 25 $Omega$. cm) The main results obtained are as follows : 1) The total weight loss and weight loss rate of affected zone of weldment by corrosion-erosion in the sea water are more increased than that of base metal. 2) The electrode potential by corrosion-erosion in the sea water becomes less noble than that of base metal, and current density is more increased. 3) As time goes by, the total weight loss and weight loss rate by cavitation erosion-corrosion in air-liquid 2 phase flow become more increased then those in only liquid solution. but these values turn to be decreased.