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Page : 95 - 101
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- 산성 염화물 환경에서 F53 슈퍼 듀플렉스 스테인리스강의 2 상간의 공식 거동 연구
- The pitting corrosion behaviors between the constituent phases in F53 super duplex stainless steel (SDSS) in acidified chloride environments were investigated using a critical pitting corrosion temperature test, a potentiodynamic anodic polarization test, and the microstructure analyses through a SEM-EDS and a SAM. As the solution annealing temperature decreased from 1150℃ to 1050℃, the γ-phase fraction increased whereas the α-phase fraction decreased. The pitting potential and the critical pitting temperature increased with a decrease of solution annealing temperature, thereby increasing the resistance to pitting corrosion. The pitting corrosion of the SDSS was selectively initiated at the α-phases because the PREN (pitting resistance equivalent number, PREN = %Cr+3.3%Mo+30%N) value of the γ-phase is much larger than that of the α-phase, irrespective of the solution annealing temperature. The pitting corrosion was finally propagated from the α-phase to the γ-phase. The decrease of solution annealing temperature enhanced the resistance to pitting corrosion greatly in acidified chloride environments due to a decrease of PREN difference between the γ-phase and the α-phase, that is, a decrease of PRENγ by dilution of N in γ-phase with an increase in the γ-phase volume fraction and an increase of PRENα by enrichment of Cr and Mo in the α-phase with a decrease in the α-phase volume fraction.
- KEYWORDs : super duplex stainless steel, potentiodynamic polarization, critical pitting temperature, SEM-EDS, PREN
- AUTHORs : 김순태†·공경호·이인성·박용수·이종훈·김두현
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Page : 102 - 106
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- Ni-Mn 전착층의 기계적 성질에 미치는 공정조건의 영향
- Nickel electrodeposition from sulfamate bath has several benefits such as low internal stress, high current density and good ductility. In nickel deposited layers, sulfur induces high temperature embrittlement, as Ni-S compound has a low melting temperature. To overcome high temperature embrittlement problem, adding manganese is one of the good methods. Manganese makes Mn-S compound having a high melting temperature above 1500℃. In this work, the mechanical properties of Ni-Mn deposited layers were investigated by using various process variables such as concentration of Mn(NH2SO3)2, current density, and bath temperature. As the Mn content of electrodeposited layers was increased, internal stress and hardness were increased. By increasing current density, internal stress increased, but hardness decreased. With increasing the bath temperature from 55 to 70℃, internal stress of Ni deposit layers decreased, but hardness didn\'t change by bath temperature. It was likely that eutectoid manganese led to lattice deformation, and the lattice deformation increased hardness and internal stress in Ni-Mn layers. Increasing current density and decreasing bath temperature would increase a mount of H2 absorption, which was a cause for the rise of internal stress.
- KEYWORDs : Ni-Mn, electrodeposition, internal stress, hardness, sulfamate bath
- AUTHORs : 신지웅·양승기·황운석†
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Page : 107 - 111
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- 착화제와 pH가 무전해 Ni-Co-P 도금 피막의 석출거동에 미치는 영향
- Electroless plated Ni-Co-P films have been used to suppress the electromagnetic waves from magnetic recording media, and the suppression is known to be achieved with films made with optimized plating composition and plating condition. Effects of complexing agents on the deposition rate and bath stability of Ni-Co-P film were studied using sodium citrate, sodium tartrate and multi-complex agents containing both of them. Deposition of electroless Ni-Co-P platings was dependent upon the complexing agents. Deposition rate was twice when using sodium tartrate compared to that using sodium citrate. And it was slightly slower with multi-complex agents than with sodium tartrate, bath stability being declined in the former. Deposition rate increased with increasing pH until pH 11. Excellent bath stability and good deposition rate were obtained using multi-complex agent as sodium citrate 0.10 mol/L and sodium tartrate 0.15 mol/L in the electroless Ni-Co-P plating films.
- KEYWORDs : electroless plating, Ni-Co-P, deposition behavior, sodium citrate, sodium tartrate
- AUTHORs : 최벽근·양승기·신지웅·황운석†
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Page : 112 - 119
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- 증기발생기 전열관 2차측 응력부식균열의 실험실적 모사 방법
- In this work, it is aimed to develop the fabrication method of axial stress corrosion cracking (SCC) defects having various sizes, on the outer diameter surface of the steam generator (SG) tubings. To control the length of the artificial SCC defect, the specific area of the SG tubing samples was exposed to an acidic solution after a sensitization heat treatment. During the exposure to an acidic solution, a direct current potential drop (DCPD) method was adopted to monitor the crack depth. The size of the SCC defect was first evaluated by an eddy current test (ECT), and then confirmed by a destructive examination. From the comparison, it was found that the actual crack length was well controlled to be similar to the length of the surface exposed to an acidic solution (5, 10, 20 or 30 mm in this work) with small standard deviation. From in-situ monitoring of the crack depth using the DCPD method, it was possible to distinguish a non-through wall crack from a through wall crack, even though the depth of the non-through wall crack was not able to be precisely controlled. The fabrication method established in this work was useful to simulate the SCC defect having similar size and ECT signals as compared to the field cracks in the SG tubings of the operating Korean PWRs.
- KEYWORDs : direct current potential drop method, eddy current test, non-through wall crack, steam generator tubing, stress corrosion cracking, through wall crack
- AUTHORs : 이재민·김성우†·황성식·김홍표·김홍덕
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Page : 125 - 129
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- Investigation of shinning Spot Defect on Hot-Dip Galvanized Steel Sheets
- Shinning spot defects on galvanized steel sheets were studied by optical microscope, scanning electron microscope(SEM), Energy Dispersive Spectrometer (EDS) and Laser-Induced Breakdown Spectroscopy Original Position Statistic Distribution Analysis (LIBSOPA) in this study. The research shows that the coating thickness of shinning spot defects which caused by the substrate defect is much lower than normal area, and when skin passed, the shinning spot defect area can not touch with skin pass roll which result in the surface of shinning spot is flat while normal area is rough. The different coating morphologies have different effects
on the reflection of light, which cause the shinning spot defects more brighter than normal area. - KEYWORDs : shinning spot defect, coating morphologies, coating thickness, substrate defect.
- AUTHORs : LIU Yonggang and CUI Lei
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Page : 130 - 138
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- 고체입자 충돌침식으로 인한 배관 재질의 손상에 관한 연구
- Wall thinning can be classified into three types: flow-accelerated corrosion, cavitation erosion and solid particle erosion. This article presents a study of solid particle erosion, which frequently causes damages to power plants’ pipe system. Unlike previous studies, this study uses a mechanism to make solid particles
in a fluid flow collide with pipe materials in underwater condition. Experiment is conducted in three cases of velocity according to solid-water ratio using the three types of the materials of A106B, SS400, and A6061. The experiments were performed for 30 days, and the surface morphology and hardness of the materials were examined for every 7 days. Based on the velocity change of the solid particles in a fluid flow, the surface changes, the change in the amount of erosion, the erosion rate and the variation in the hardness of carbon steel and aluminum family pipe materials can all be determined. In addition, factorbased erosion rates are verified and a wall-thinning relation function is suggested for the pipe materials. - KEYWORDs : solid particle erosion, loss of pipe material, wall thinning, solid-water ratio, particle content, erosion rate, least squared method
- AUTHORs : 김경훈·최덕현·김형준
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Page : 139 - 144
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- 도장이 필요없는 내후성강 박스거더 상부 플랜지외부면 방식제 주입을 통한 방식공법 연구
- In corrosion-sensitive area of exsisting unpainted weathering steel bridge with closed box girder structure. there are some serious local corrosion problems because of rain water or dew water which can not be solved by conventional maintenance method. These problems must be technically controled because of the
influence on the safety of bridge. This study is the first stage of developing the economic corrosion control manual for these local corrosion problems. Through the injecting experiment of tar sealant into the crevice of mock-up equipment, it was proofed that the corrosive sealant can be useful to corrosion control at crevice
of corrosion sensitive area. - KEYWORDs : weathering steel, splice connection part, corrosion, corrosion sensitive area, multi-function sealant
- AUTHORs : 송 창 영
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Page : 145 - 151
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- 핵연료 피복관 부식생성물 부착에 관한 Ni/Fe 이온 농도비의 영향
- The objectives of this study are to investigate the effect of the concentration ratios of Ni and Fe ions on crud deposition onto the fuel cladding surface in the simulated primary environments of a pressurized water reactor. Crud deposition tests were conducted in the Ni and Fe concentration ratios of 20:20 ppm, 39:1 ppm and 1:39 ppm at 325℃ for 14 days. In the case of the same Ni and Fe ion ratio (20:20), nickel
ferrite with a polyhedral shape was formed. Nickel oxide deposits with a needle shape were formed in the condition of high Ni to Fe ion ratio (39:1), While polyhedral iron oxide and needle-like nickel oxide formed in the condition of low Ni to Fe ion ratio (1:39). The amount of deposits increased, when Fe oxides were formed. This indicates that Fe rich oxides stimulated Ni oxide deposition. - KEYWORDs : axial offset anomaly, ni and fe ion concentration, crud deposition, primary water chemistry
- AUTHORs : 백승헌·김우철·심희상·임경수·허도행†
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Page : 152 - 156
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- 액체급냉법에 의해 제조한 비정질 Co-Nb-B 합금의 전기화학적 부식 특성
- This study was undertaken to examine the electrochemical corrosion properties of an Co80Nb10B10 and Co82Nb8B10 amorphous alloys prepared by melt-spinning method under various conditions. The potentiodynamic polarization responses at various levels of pH (pH 2, pH 7, pH 12) showed that the corrosion current rate of Co80Nb10B10 alloy is lower than that of Co82Nb8B10 alloy in all levels of pH, implying the general corrosion resistance of the alloy with higher Nb content is better than that with higher Co content. The pitting potential of Co80Nb10B10 alloy was also better than that of Co82Nb8B10, evidenced by the higher pitting potential. Nb is thought to be effective in increasing the protectiveness of the passive film and hence to improve the corrosion resistance of Co-Nb-B alloys.
- KEYWORDs : amorphous alloys, Co-Nb-B alloys, potentiodynamic polarization, uniform corrosion, pitting
- AUTHORs : 김은선·김현구·장희진†
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Page : 163 - 169
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- The study on the influence of surface cleanness and water soluble salt on corrosion protection of epoxy resin coated carbon steel
- The corrosion resistance of epoxy-coated carbon steel was evaluated. The carbon steel surface was subjected to different treatment methods such as steel grit blasting and power tool treatment as well as contamination of water soluble salt. To study the effect of the surface treatments and contamination, the topology of the treated surface was observed by confocal microscopy and a pull-off adhesion test was conducted. The corrosion resistance of the epoxy-coated carbon steel was further examined by electrochemical impedance spectroscopy (EIS) combined with immersion test of 3.5 wt% of NaCl solution. Consequently, the surface contamination by sodium chloride with 16 mg/m2, 48 mg/m2 and 96 mg/m2 didn’t affect the adhesion strength for current epoxy coated carbon steel and blister and rust were not observed on the surface of epoxy coating contaminated by various concentration of sodium chloride after 20 weeks of immersion in 3.5 wt% NaCl aqueous solutions. In addition, the results of EIS test showed that the epoxy-coated carbon steel treated
with steel grit blasting and power tool showed similar corrosion protection performance and surface cleanness such as Sa 3 and Sa 2.5 didn’t affect the corrosion protectiveness of epoxy coated carbon steel. - KEYWORDs : EIS, epoxy, blasting, hygrothermal, blister
- AUTHORs : MinYoung Shon†
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