http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
순환동전위 분극실험을 이용한 스테인리스강의 그린데스용액에서 전기화학적 특성에 미치는 온도의 영향
황현규 ( Hyun-kyu Hwang ),김성종 ( Seong-jong Kim ) 한국부식방식학회 2021 Corrosion Science and Technology Vol.20 No.5
Since 2020, the International Maritime Organization (IMO) has updated regulations on the sulfur content to be less than 0.5% in exhaust gas emitted from ships. Accordingly, the exhaust gas post-treatment device for ships, which is SOx/NOx reduction technology, was introduced. However, the exhaust gas post-treatment device is suffering corrosion because of the harsh corrosive environment formed by sulfate and chlorine oxide through the desulfurization process. In this investigation, cyclic potentiodynamic polarization (CPDP) experiment for UNS S31603 and UNS N08367 was performed in a green death solution that simulates the environment of a desulfurization device. The corrosion rate of UNS S31603 at the highest temperature was about 3 times higher than that of UNS N83067. Also, electron microscope scan revealed corrosion type UNS N83067 presents intergranular corrosion tendency. On the other hand, UNS S31603 was observed as general corrosion. The α values of UNS N08367 at 30℃ and 60 ℃ were higher than those of UNS S31603, thus UNS N08367 is considered to have a higher local damage tendency. Whereas, since the α value of UNS S31603 at 90 ℃ is larger than that of UNS N08367, UNS S31603 is considered to have a higher local damage trend.
다구찌 기법을 활용한 통계적·표면 분석에 따른 오스테나이트 스테인리스강의 전해연마조건 최적화 연구
황현규 ( Hyun-kyu Hwang ),김성종 ( Seong-jong Kim ) 한국부식방식학회 2022 Corrosion Science and Technology Vol.21 No.5
Electropolishing has various parameters because an electrochemical reaction is applied. Accordingly, experiments to determine factors and levels of electropolishing conditions are in progress for various materials. The purpose of this investigation was to optimize conditions for electropolishing using the taguchi method for UNS S31603. Factors such as electrolyte composition ratio, electrolyte temperature, and electropolishing process time were selected. Electropolishing was optimized using analysis of variance (ANOVA), signal-to-noise ratio (the smaller the better characteristics), and surface analysis. Results of ANOVA revealed that only the electrolyte composition ratio among factors was effective for surface roughness. As a result of statistical analysis of the signal-to-noise ratio, the highest signal-to-noise ratio was calculated under electropolishing conditions with sulfuric acid and phosphoric acid ratio of 4:6, an electrolyte temperature of 75 ℃, and electropolishing process time of 7 minutes. In addition, the surface roughness after electropolishing under the above conditions was 0.121 μm, which was improved by more than 88% compared to mechanical polishing.
슈퍼오스테나이트 스테인리스강의 해수환경에서 온도에 따른 전기화학적 특성
황현규 ( Hyun-kyu Hwang ),김성종 ( Seong-jong Kim ) 한국부식방식학회 2021 Corrosion Science and Technology Vol.20 No.6
In this investigation, the electrochemical characteristics of superaustenitic and general austenitic stainless steels were compared by conducting potentiodynamic polarization experiment with varying temperatures in natural seawater solution. From the result of the potentiodynamic polarization experiment, the corrosion rate of UNS S31603 was found to be 17 times faster than that of UNS N08367 under the most severe corrosion conditions. The relationship between the corrosion rate by maximum damage depth and the corrosion rate by the corrosion current density was expressed as α value for each stainless steel. The α value of UNS S31603 under all temperature conditions was higher than that of UNS N08367 under similar conditions. This means that UNS S31603 is more prone to localized corrosion than UNS N08367. UNS S31603 expressed pitting type damages under all temperature conditions as shown by SEM analysis results. The pitting damage rapidly grew at the relatively poor grain boundaries. Damage on UNS N08367 was not clearly represented at 30 ℃ and 60 ℃, and slight intergranular corrosion damage was observed on the entire surface at 90 ℃.
Al 6061-T6 합금의 해수 내 캐비테이션 진폭에 따른 캐비테이션-침식 조건하에서 전기화학적 특성
황현규 ( Hyun-kyu Hwang ),김성종 ( Seong-jong Kim ) 한국부식방식학회(구 한국부식학회) 2020 Corrosion Science and Technology Vol.19 No.6
Generally, Al alloys of 5000 and 6000 series show excellent weldability, workability, and specific strength, and are widely used in ship building. A combined experiment via cavitation erosion and corrosion damage involving 6061-T6 Al alloy was performed using potentiodynamic polarization under cavitation erosion (hybrid experiments) with amplitude (cavitation strength). The corrosion current density was approximately 52-fold higher at 30 μm than under static conditions, suggesting that the amplitude greatly affected the damage. The degree of damage increased with increasing cavitation amplitude. After the hybrid experiment, the corrosion rate was compared according to the weight loss and damage depth, and the relationship between the two values was expressed as alpha value. The alpha (α) values at amplitudes of 5 μm, 10 μm and 30 μm were 5.11, 12.81 and 8.74, respectively, suggesting that the α value at 10 μm was greater than at 5 μm, and indicating local corrosion damage. However, the α value at 30 μm was smaller than that of 10 μm, which is attributed to higher damage via uniform corrosion than damage induced by local corrosion.
슈퍼오스테나이트 스테인리스강의 순환동전위 분극특성에 미치는 해수온도의 영향과 손상 거동에 관한 미시적 분석
황현규 ( Hyun-kyu Hwang ),김성종 ( Seong-jong Kim ) 한국부식방식학회 2021 Corrosion Science and Technology Vol.20 No.6
Because austenitic stainless steel causes localized corrosion such as pitting and crevice corrosion in environments containing chlorine, corrosion resistance is improved by surface treatment or changes of the alloy element content. Accordingly, research using cyclic potentiodynamic polarization experiment to evaluate the properties of the passivation film of super austenitic stainless steel that improved corrosion resistance is being actively conducted. In this investigation, the electrochemical properties of austenitic stainless steel and super austenitic stainless steel were compared and analyzed through cyclic potentiodynamic polarization experiment with varying temperatures. Repassivation properties were not observed in austenitic stainless steels at all temperature conditions, but super austenitic stainless steels exhibited repassivation behaviors at all temperatures. This is expressed as α values using a relational formula comparing the localized corrosion rate and general corrosion rate. As the α values of UNS S31603 decreased with temperature, the tendency of general corrosion was expected to be higher, and the α value of UNS N08367 increased with increasing temperatures, so it is considered that the tendency of localized corrosion was dominant.
배관의 부식 상태 진단에 사용되는 ER 부식센서의 가속부식환경에서의 신뢰성 평가
황현규 ( Hyun-kyu Hwang ),신동호 ( Dong-ho Shin ),김헌희 ( Heon-hui Kim ),이정형 ( Jung-hyung Lee ) 한국부식방식학회 2021 Corrosion Science and Technology Vol.20 No.6
In this study, the reliability of a commercial ER-type corrosion sensor was evaluated under an accelerated corrosion environment to verify its suitability for application in monitoring of ship’s seawater piping system. A closed-loop pump piping testbed was designed and constructed to compare the wall thickness reduction of the pipe and the response from the sensor. The sensor was attached inside the pipe near the outlet of the pump that was exposed to a 3.5% NaCl solution with or without copper accelerated acetic acid (CASS). The results demonstrated that the presence of CASS significantly increased the corrosivity of the solution as well as the thickness reduction of the pipe, as expected. On the other hand, the corrosion products formed by the solution with CASS were thicker compared with those without CASS. The sensor response to temperature variation was found to be a clear linear relationship for the solution without CASS but there was a non-linear relationship where CASS was present.
전해연마한 슈퍼오스테나이트 스테인리스강의 해수온도에 따른 전기화학적 특성 연구
황현규 ( Hyun-kyu Hwang ),김성종 ( Seong-jong Kim ) 한국부식방식학회 2023 Corrosion Science and Technology Vol.22 No.3
Electropolishing technology uses an electrochemical reaction and improves surface roughness, glossiness, and corrosion resistance. In this investigation, electropolishing was performed to improve the corrosion resistance of super austenitic stainless steel. As a result of electropolishing, surface roughness (0.16 μm) was improved by about 76.5% compared to mechanical polishing (0.68 μm). In addition, the electropolished surface was smooth because the average and variance values of the depth histogram were small. Tafel analysis was performed after a potentiodynamic polarization experiment with seawater temperature, and the microstructure was compared and analyzed. The corrosion current density at 30 ℃, 60 ℃, and 90 ℃ was reduced by 0.083 μA/cm<sup>2</sup>, 0.296 μA/cm<sup>2</sup>, and 0.341 μA/cm<sup>2</sup>, respectively. Pitting occurred in the mechanical polished specimen at 30 °C, but partial intergranular corrosion was observed in the electropolished specimen, and pitting occurred predominantly at both 60 ℃ and 90 ℃. In addition, the damage depths of the electropolished specimen were shallower than those of mechanical polishing at 30 ℃ and 60 ℃, but the opposite result was seen at 90 ℃.
부산도시철도 2호선 VVVF 인버터 개량 연구 (A study on refurbishing VVVF Inverter for train of Busan metro line 2)
황현규(Hyun-Gyu Hwang),박희철(Hee-Chul Park),이은규(Eun-Kyu Lee),권선범(Sun-Bum Kwon) 한국철도학회 2011 한국철도학회 학술발표대회논문집 Vol.2011 No.5
This paper studied on the VVVF Inverter for 1C4M propulsion system of railway traction. The paper includes the comparsion along a VVVF Inverter electric power conversion element for an electric railcar(GTO, IGBT). These inverters are composed of high power IGBTs and controlled by compact control units. The stack is simplified and optimized by using plate bus and IGBT driver units of hybrid-type.
알루미늄 6061-T6 합금에 대한 양극산화층이 해수 내 부식 및 응력부식균열에 미치는 영향
신동호(Dong-Ho Shin),황현규(Hyun-kyu Hwang),정광후(Kwang-Hu Jung),김성종(Seong-Jong Kim) 한국표면공학회 2020 한국표면공학회지 Vol.53 No.5
This paper investigated the characteristics of anodized aluminum 6061-T6 alloy for corrosion and stress corrosion cracking(SCC) under natural seawater. The hard anodizing oxide film formed on the 6061-T6 was a uniform thickness of about 25 μm. The corrosion characteristics were performed with a potentiodynamic polarization test. SCC was characterized by a slow strain rate tensile test under 0.005mm/min rate. As a result, the anodizing film showed no significant effect on SCC in the slow strain rate test. However, the corrosion current density of base metal was measured to be approximately 13 times higher than that of the anodized specimen. Therefore, the anodizing film significantly improved the corrosion resistance of 6061-T6 alloy in natural seawater.