한국부식방식학회

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Page : 312 - 317 DOWNLOAD
AA1100의 부식에 미치는 Na2S, NaCl, H2O2 농도의 영향
The objective of this study was to investigate the corrosion behavior of aluminum (AA1100) in a mixed solution of 0 ~ 0.1 g/L Na2S + 0.3 ~ 3 g/L NaCl + 0 ~ 10 mL/L H2O2. Potentiodynamic polarization tests were performed. Effects of solution compositions on corrosion potential, corrosion rate, and pitting potential of aluminum were statistically analyzed with a regression model. Results suggested that localized
corrosion susceptibility of aluminum was increased in the solution with increasing concentration of NaCl because the pitting potential was lowered linearly with increasing NaCl concentration. On the contrary, H2O2 mitigated the galvanic corrosion of aluminum by increasing the corrosion potential. It also mitigated
localized corrosion by increasing the pitting potential of aluminum. Na2S did not exert a noticeable effect on the corrosion of aluminum. These effects of different chemical species at various concentrations were independent of each other. Synergy or offset effect was not observed.
KEYWORDs : Corrosion, Regression analysis, Hydrogen peroxide, Sodium chloride, Sodium sulfide
AUTHORs : 이주희·장희진†

Page : 300 - 311 DOWNLOAD
3.5% NaCl 수용액 내 TWIP강의 부식거동에 미치는 합금원소 (Cu, Al, Si)의 영향
The corrosion behaviors of twinning-induced plasticity (TWIP) steels with different alloying elements (Cu, Al, Si) in a neutral aqueous environment were investigated in terms of the characteristics of the corrosion products formed on the steel surface. The corrosion behavior was evaluated by measuring potentiodynamic polarization test and electrochemical impedance spectroscopy. For compositional analysis of the corrosion products formed on the steel surface, an electron probe x-ray micro analyzer was also utilized. This study showed that the addition of Cu to the steel contributed to the increase in corrosion resistance to a certain extent by the presence of metallic Cu in discontinuous form at the oxide/steel interface. Compared to the case of steel with Cu, the Al-bearing specimen exhibited much higher polarization resistance and lower corrosion current by the formation of a thin Al-enriched oxide layer. On the other hand, Si addition (3.0 wt%) to the steel led to an increase in grain size, which was twice as large as that of the other specimens,
resulting in a deterioration of the corrosion resistance. This was closely associated with the localized corrosion attacks along the grain boundaries by the formation of a galvanic couple with a large cathode-small anode.
KEYWORDs : Twinning-induced plasticity steel, Corrosion, Polarization resistance, Large cathode-small anode
AUTHORs : 김시온·황중기†·김성진†

Page : 292 - 299 DOWNLOAD
해수 유속 변화에 따른 Al5052-O와 Al6061-T6 알루미늄 합금의 침식부식 특성
The hull material of a high-speed ship may cause erosion damage from fluid impact. When physical erosion and electrochemical corrosion combine, erosion corrosion damage occurs. The aluminum ship is vulnerable to erosion corrosion because it can be operated at high speed. Thus, in this study, Al5052-O and Al6061-T6
aluminum alloys for the marine environment were selected as experimental materials. The erosion corrosion resistance of Al5052-O and Al6061-T6 aluminum alloys in seawater was investigated by an erosion test and potentiodynamic polarization test at the various flow rate (0 m/s, 5 m/s, 10 m/s, 15 m/s, 20 m/s). Erosion corrosion characteristics were evaluated by surface analysis, 3D analysis, SEM analysis, and the Tafel extrapolation method. The results of surface damage analysis after the erosion test showed that Al6061-T6 presented better erosion resistance than Al5052-O. The results of the potentiodynamic polarization test at the various flow rate, corrosion current density by Tafel extrapolation presented lower values of Al6061-T6
than Al5052-O. Al5052-O showed more surface damage than Al6061-T6 at all flow rates. Consequently, Al6061-T6 presented better erosion corrosion resistance than Al5052-O. The results of this study are valuable data for selecting hull material for an aluminum alloy vessel.
KEYWORDs : Aluminum alloy, Erosion corrosion, Potentiodynamic polarization experiment, Seawater, Surface damage
AUTHORs : 김영복·김성종†

Page : 285 - 291 DOWNLOAD
650 °C 의 SO2 가스 환경 하에서 T22와 T92 강의 고온 부식특성
In this study, the corrosion characteristics of T22 and T92 steel were investigated in 6O2 + 16CO2 + 2SO2 gas environment at 650 °C. Corrosion characteristics were characterized by weight gain, oxide layer thickness, scanning electron microscope, optical microscope, energy dispersive X-ray spectroscopy, and X-ray diffraction.
T22 and T92 steel tended to stagnate oxide layer growth over time. Oxidation kinetics were analyzed using the data of oxide layer thickness, and a regression model was presented. The regression model was significantly acceptable. The corrosion rate between the two steels through the regression model showed significant difference.
The T92 steel was approximately twice as large as the time exponent and showed very good corrosion resistance compared to the T22 steel. In both steels, the oxide layer mainly formed a Fe-rich oxide layer composed of hematite (Fe2O3), magnetite (Fe3O4), and spinel (FeCr2O4). Sulfide segregation occurred in the oxide layer due to SO2 gas. However, the locations of segregation for the T22 and T92 steel were
different.
KEYWORDs : T22, T92, High-temperature, Corrosion, SO2 gas
AUTHORs : 정광후·김성종†

Page : 277 - 284 DOWNLOAD
Effect of Applied Voltage on the Reliability of Coating Flaw Detection of Pipe with Different Buried Depths
External corrosion control of buried pipe can be achieved by the combination of barrier coating and cathodic protection. Coating damage and deterioration can be induced by many reasons; damage during handling and laying, enhanced failure at low temperatures, failure during commissioning and operation, disbanding due to inadequate surface cleaning, rock penetration during installation and service etc. This work focused on the effect of survey conditions on the reliability of coating flaw detection of buried pipes. The effects of applied voltage and anode location on the detection reliability of coating flaw of buried pipe in soil with the resistivity of ca. 25.8 kΩ·cm were discussed. Higher applied voltage increased the detection reliability,
regardless of buried depth, but deeper burial depth reduced the reliability. The location of the anode has influenced on the detection reliability. This behaviour may be induced by the variation of current distribution by the applied voltage and buried depth. From the relationship between the applied voltage and reliability, the needed detection potential to get a desire detection reliability can be calculated to get 100% detection reliability using the derived equation.
KEYWORDs : Buried pipe, Coating flaw detection, Buried depth, Detection potential, Reliability
AUTHORs : B. T. Lim, M. G. Kim, K. T. Kim, H. Y. Chang, and Y. S. Kim†

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Effect of Heat Treatment Conditions on Corrosion and Hydrogen Diffusion Behaviors of Ultra-Strong Steel Used for Automotive Applications
The purpose of this study was to examine the influence of conditions for quenching and/or tempering on the corrosion and hydrogen diffusion behavior of ultra-strong automotive steel in terms of the localized plastic strain related to the dislocation density, and the precipitation of iron carbide. In this study, a range of analytical and experimental methods were deployed, such as field emission-scanning electron microscopy, electron back scatter diffraction, electrochemical permeation technique, slow-strain rate test (SSRT), and electrochemical polarization test. The results showed that the hydrogen diffusion parameters involving the diffusion kinetics and hydrogen solubility, obtained from the permeation experiment, could not be directly
indicative of the resistance to hydrogen embrittlement (HE) occurring under the condition with low hydrogen concentration. The SSRT results showed that the partitioning process, leading to decrease in localized plastic strain and dislocation density in the sample, results in a high resistance to HE-induced by aqueous corrosion. Conversely, coarse iron carbide, precipitated during heat treatment, weakened the long-term corrosion resistance. This can also be a controlling factor for the development of ultra-strong steel with superior corrosion and HE resistance.
KEYWORDs : Ultra-strong steel, Heat treatment, Corrosion induced hydrogen diffusion, Residual stress, Carbides
AUTHORs : Jin-seong Park, Hwan Goo Seong, and Sung Jin Kim†

Page : 258 - 266 DOWNLOAD
Study on Corrosion Properties of Additive Manufactured 316L Stainless Steel and Alloy 625 in Seawater
The objective of this study was to evaluate corrosion resistance of additive manufactured 316L stainless steel and alloy 625 powders widely used in corrosion resistance alloys of marine industry in comparison with cast alloys. Directed Energy Deposition (DED) method was used in this work for sample production.DED parameter adjustment was also studied for optimum manufacturing and for minimizing the influence of defects on corrosion property. Additive manufactured alloys showed lower corrosion resistance in seawater compared to cast alloys. The reason for the degradation of anti-corrosion property was speculated to be due to loss of microstructural integrity intrinsic to the additive manufacturing process. Application of heat treatment with various conditions after DED was attempted. The effect of heat treatments was analyzed with a microstructure study. It was found that 316L and alloy 625 produced by the DED process could recover their expected corrosion resistance when heat treated at 1200 °C.
KEYWORDs : Additive manufacturing, Corrosion, 3D printing, Nickel alloy, Directed energy deposition(DED)
AUTHORs : Geun-Su Jung, Yong-Ha Park, Dae-Jung Kim, and Chae-Seon Lim†

Page : 253 - 257 DOWNLOAD
Deep Learning Based Real-Time Painting Surface Inspection Algorithm for Autonomous Inspection Drone
A deep learning based real-time painting surface inspection algorithm is proposed herein, designed for developing an autonomous inspection drone. The painting surface inspection is usually conducted manually. However, the manual inspection has a limitation in obtaining accurate data for correct judgement on the surface because of human error and deviation of individual inspection experiences. The best method to replace manual surface inspection is the vision-based inspection method with a camera, using various image processing algorithms. Nevertheless, the visual inspection is difficult to apply to surface inspection due to diverse appearances
of material, hue, and lightning effects. To overcome technical limitations, a deep learning-based pattern recognition algorithm is proposed, which is specialized for painting surface inspections. The proposed algorithm functions in real time on the embedded board mounted on an autonomous inspection drone. The inspection
results data are stored in the database and used for training the deep learning algorithm to improve performance. The various experiments for pre-inspection of painting processes are performed to verify real-time performance of the proposed deep learning algorithm.
KEYWORDs : Surface inspection, Deep learning, Inspection drone, Real-time inspection
AUTHORs : Hyung-young Chang, Seung-ryong Han, and Heon-young Lim†

Page : 243 - 252 DOWNLOAD
Corrosion Behavior and Inhibition Studies of AZ31B Magnesium Alloy With and Without Cl- in the Alkaline Electrolytes in Addition with Various Inhibitor and Without Cl- in the Alkaline Electrolytes in Addition with Various Inhibitor Additives
The pitting corrosion and inhibition studies of AZ31B magnesium alloy were investigated in the alkaline solution (pH12) with chloride and inhibitors. The corrosion behavior of passive film with/without Cl- in the alkaline electrolyte were conducted by polarization curve and immersion tests in the presence of various
additives (inhibitors) to clarify the inhibition efficiency of pitting corrosion at higher potential region. Critical concentration of pitting corrosion for Mg alloy was evaluated with 0.005 M NaCl in 0.01 M NaOH on the anodic polarization behavior. Critical pitting of AZ31B Mg alloy in 0.01 M NaOH is a function of chlorides; Epit = - 1.36 – 0.2 log [Cl–]. When the Sodium Benzoate (SB) was only used as an inhibitor,
a few metastable pits developed on the Mg surface by an immersion test despite no pitting corrosion on the polarization curve meaning that adsorption of SB on the surface is insufficient protection from pitting corrosion in the presence of chloride. The role of SB and Sodium Dodecylbenzenesulfonate (SDBS) inhibitors for the Mg alloy surface in the presence of chloride was suppressed from pitting corrosion to co-adsorb on the Mg alloy surface with strong formation of passive film preventing pitting corrosion.
KEYWORDs : Magnesium alloy, Corrosion inhibitor
AUTHORs : Yoonji Shin and Kyehyun Cho†

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Analysis of PVDF Coating Properties with Addition of Hydrophobically Modified Fumed Silica
In this study, hydrophobically modified fumed silica was added to the PVDF coating to improve corrosion protection performance. Two types of silane modifiers, trimethylchlorosilane (TMCS) and hexamethyldisilazane (HMDZ), were used for hydrophobic modification of the fumed silica. The composition of modified fumed
silica was analyzed by Fourier transform infrared, X-ray photoelectron spectroscopy, and elemental analysis. The dispersion of modified fumed silica in the PVDF coating was observed by the transmission electron microscopy, and the hydrophobicity of PVDF coating was analyzed by the water contact angle. Surface
properties were examined by the field emission scanning electron microscopy and scanning probe microscopy. Potentiodynamic polarization was conducted to confirm corrosion protection performance of PVDF coating in terms of hydrophobically-modified fumed silica contents. As a result, the average surface roughness and
the water contact angle of the PVDF coating increased with modifier contents. The results of the potentiodynamic polarization test showed an increase of the Ecorr values with increase of the hydrophobicity of PVDF coating. Thus, it clearly indicates that the corrosion protection performance of PVDF coating improved with the addition of the hydrophobic-modified fumed silica that prevents the penetration of moisture into the PVDF coating.
KEYWORDs : Polyvinylidene fluoride, Hydrophobic modification, Fumed silica
AUTHORs : Nam Kyu Lee, Young Hoon Kim, Tae Gyu Im, Dong Uk Lee, MinYoung Shon, and Myung Jun Moon†

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