• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.32 no.3
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• pp.294-301
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• 1996

To improve the corrosion resistance of stainless steel and Fe, the adherence between fIlm and substarte and the corrosion resistance to ceramic fIlm ($TiO_2$ and $ZrO_2$), coated by RF magnetron sputtering, were studied. The adherence index (X) was determined by the measure of micro - hardness test. Also, the corrosion resistance on oxide coatings was studied using electrochemical measurement. The main results obtained are as the following: 1) In the micro - hardness test, with 1J.UI1 thickness fIlm, it has only one the value of X. Above 2J.UI1 thickness fIlm, however, get another value ofX as the cracks in fIlm. 2) The adhensivity of titania ($TiO_2$) coated fIlm is superior to that of zirconia ($ZrO_2$) coated fIlm. 3) All oxide fIlm used adhere well on the mild materials such as pure steel than high intensity materials like stainless steel. 4) The corrosion resistance of zirconia coated materials was improved compared to titania coated materials.

• Journal of the Korean Chemical Society
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• v.57 no.2
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• pp.272-278
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• 2013

Extract of ginger has been evaluated as a green inhibitor for the corrosion of steel in sulfide polluted NaCl solution using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and electrochemical frequency modulation (EFM) techniques. Potentiodynamic polarization measurements showed that this extract acts as a mixed type inhibitor but mainly inhibits the cathodic reaction. The inhibition efficiency was found to increase with inhibitor concentration reaching to approximately 83.9% using 250 ppm of ginger. Nyquist plots show a single capacitive loop in uninhibited and inhibited solutions. From EFM the causality factors are very close to theoretical values which indicate that the measured data are of good quality. The adsorption process of the studied extract on steel surface obeys Temkin adsorption isotherm. The results obtained from the different electrochemical techniques were in good agreement which prove the validity of these tools in measurement of corrosion rate. Ginger extract has no effect on Escherichia Coli and can be applied safely on waste water treatment plants.

• Journal of the Korean institute of surface engineering
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• v.36 no.6
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• pp.423-429
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• 2003

It has been investigated corrosion resistance and crystal structure of Zn-Cr coatings fabricated by electroplating method and electron-beam physical vapor deposition method(EB-P VD). The electroplated Zn-Cr alloy consists mainly of η'-Zn phase for the lower Cr content than 7.9 wt% Cr and ${\gamma}$'-ZnCr phase for the higher Cr content. In the Zn-Cr alloy fabricated by EB-PVD the ${\gamma}$'-ZnCr phase appeared clearly at 3 wt% Cr and it became the sole phase at 50 wt%Cr. The amount of η'-Zn phase decreased obviously with increasing Cr content when it exceeded 15 wt% Cr. The electrochemical measurement of the electroplated Zn-Cr film has shown corrosion potential of about -1000 mV. The current density of active region and the amount of dissolved Zn and Cr decreased significantly with increasing Cr content. The electrochemical characteristics of Zn-Cr alloy fabricated by EB-PVD have shown that the alloy of 50 wt% Cr had the highest corrosion potential(-500 mV) and the lowest critical passive current density than that of the electroplated.

• Journal of Advanced Marine Engineering and Technology
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• v.31 no.6
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• pp.744-752
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• 2007

Recently a fuel oil of the diesel engine in the ship is being changed with low quality as the oil price is higher more and more. Therefore the wear and corrosion in all parts of the engine like cylinder liner ring groove of piston crown, spindle and seat ring of exhaust valve are increased with using of heavy oil of low quality In particular the degree of wear and corrosion in between valve spindle and seat ring are more serious compared to the other parts of the engine due to operating in severe environment such as the high temperature of exhaust gas and repeating impact. Thus the repair weld to the valve spindle and seat ring is a unique method to prolong the life of the exhaust valve in an economical point of view In this study. corrosion property of both weld metal zone and base metal was investigated with some electrochemical methods such as measurement of corrosion potential, cathodic and anodic polarization curves, cyclic voltammogram and polarization resistance etc. in 5% $H_2SO_4$ solution. in the case of being welded with some welding methods and welding materials to the exhaust valve specimen as the base metal. In all cases. the values of hardness of the weld metal zone were more high than that of the base metal. And their corrosion resistance were also superior to the base metal. The weld metal of A2F(AC SMAW: 2 pass welding with foreign electrode) showed a relatively good results to the corrosion resistance as well as the hardness compared to the ether welding methods and welding materials. Moreover it indicated that hardness of the weld metal by the domestic electrode was considerably high compared to that of the foreign electrode.

• Journal of the Korean Society for Nondestructive Testing
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• v.31 no.1
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• pp.24-31
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• 2011

In order to measure corrosion level of reinforcement rebar in RC structures, non-destructive test methods which are concrete surface current density method and infrared thermographic technique were employed to measure corrosion levels. Experimental test parameters were various levels of corrosion states(0, 1, 3, 5, 7% of weight loss) and concrete cover depth(30 mm, 40 mm) and two different reinforcing rebar arrangements. The larger amount of concrete surface current density, the higher corrosion level in reinforcement rebar. The laboratory conditions which are ambient temperature and humidity have negligible effect on the infrared thermographical data. After analysis of current density and temperature distribution from concrete surface, corrosion level of reinforcement rebar embedded in concrete can be measured qualitatively based on the amount of electric current and heat flux.

• Corrosion Science and Technology
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• v.17 no.1
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• pp.20-29
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• 2018

Ti and its alloys show the excellent corrosion resistance to chloride environments, but they show less corrosion resistance in HCl, $H_2SO_4$, NaOH, $H_3PO_4$, and especially HF environments at high temperature and concentration. In this study, we used the commercially pure titanium and Ti-6Al-4V alloy, and evaluated the effect of the manufacturing process on the electrochemical properties. We used commercial products of rolled and forged materials, and made additive manufactured materials by DMT (Directed Metal Tooling) method. We annealed each specimen at $760^{\circ}C$ for one hour and then air cooled. We performed anodic polarization test, AC impedance measurement, and Mott-Schottky plot to evaluate the electrochemical properties. Despite of the difference of its microstructure of CP-Ti and Ti-6Al-4V alloys by the manufacturing process, the anodic polarization behavior was similar in 20% sulfuric acid. However, the addition of 0.1% hydrofluoric acid degraded the electrochemical properties. Among three kinds of the manufacturing process, the electrochemical properties of additive manufactured CP-Ti, and Ti-6Al-4V alloys were the lowest. It is noted that the test materials showed a Warburg impedance in HF acid environments.

• Corrosion Science and Technology
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• v.19 no.3
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• pp.109-114
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• 2020

The photo-reflectance of aluminum and AISI 304 stainless steel during cyclic immersion test in 3 wt% NaCl solution was examined in this study. Overall, corrosion was not recognized by a visual inspection or weight measurement up to 310 h. When evaluated, it was noted that the roughness of the specimens did not change significantly. However, localized corrosion, which is located at the vicinity of intermetallic precipitation of aluminum or at the grain boundary of stainless steel, was confirmed by the use of an optical microscope and scanning electron microscopy after tens of hours of utilizing the corrosion test. In this respect, an increase of the peak intensity for metallic Al after 90 h of test, and for metallic Fe after 153 h was detected from the X-ray photoelectron spectra. In this context, it was shown that from the photo-reflectance spectra, the reflection of the visible light from the tested samples was changed noticeably over the test duration. As a result, the intensity of reflected light was decreased up to 90 h ~ 153 h, and thereafter was shown to increase higher than the initial intensity before the corrosion test.

• Korean Journal of Metals and Materials
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• v.48 no.8
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• pp.757-764
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• 2010

We report on the effect of additives on the microstructure and corrosion properties of electrodeposited Cu films. Copper films were fabricated by electrodeposition on various concentrations of gelatin in a copper sulfate electrolyte. The surface morphologies of the Cu films were observed using a scanning electron microscope (SEM), and crystal orientation of the Cu films was analyzed by X-ray diffraction measurement. (220) plane was the dominant orientation when the films were fabricated at ambient temperature, decreasing in dominance with addition of gelatin. On the other hand, (111) plane-Cu films were preferentially grown at $40^{\circ}C$, and were also diminished with adding additives. Corrosion rate measurements using the Tafel extrapolation method based on corrosion potential and current reveal the effect of additives on corrosion behavior. Corrosion behavior was found to be strongly related to the orientation of the films. Consequently, additives like gelatin influence crystal orientation of the films, and if a less dense crystal plane, e.g. (220), is preferentially oriented during electrodeposition, a lower corrosion rate could be produced, since the plane shows a lower current density.

• Smart Structures and Systems
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• v.29 no.2
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• pp.301-309
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• 2022

Protective coatings are most widely used anticorrosive structures for steel structures. The corrosion under the coating damages the host material, but this damage is completely hidden. Therefore, a field-applicable under-coating-corrosion visualization method has been desired for a long time. Laser ultrasonic technology has been studied in various fields as an in situ nondestructive inspection method. In this study, a comparative analysis was carried out between a guided-wave ultrasonic propagation imager (UPI) and pulse-echo UPI, which have the potential to be used in the field of under-coating-corrosion management. Both guided-wave UPI and pulse-echo UPI were able to successfully visualize the corrosion. Regarding the field application, the guided-wave UPI performing Q-switch laser scanning and piezoelectric sensing by magnetic attachment exhibited advantages owing to the larger distance and incident angle in the laser measurement than those of the pulse-echo UPI. Regarding the corrosion visualization methods, the combination of adjacent wave subtraction and variable time window amplitude mapping (VTWAM) provided acceptable results for the guided-wave UPI, while VTWAM was sufficient for the pule-echo UPI. In addition, the capability of multiple sensing in a single channel of the guided-wave UPI could improve the field applicability as well as the relatively smaller size of the system. Thus, we propose a guided-wave UPI as a tool for under-coating-corrosion management.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 1999.05a
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• pp.107-108
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• 1999