한국부식방식학회

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Page : 147 - 152 DOWNLOAD
부식전위 기준에 의한 철근콘크리트 구조물의 부식진단의 위험성에 관한 고찰
Corrosion of steel reinforcement is a major factor in the deterioration of harbour and bridge structure. Steel corrosion in concrete must be checked for assessing the condition of a reinforced concrete structure. There are several ways how to measure the corrosion condition of reinforced concrete, but the corrosion potential
measurement is a very simple, rapid, cost-effective and non-destructive technique to evaluate the severity of corrosion in reinforced concrete structure, therefore commonly used by engineers. However some particular situations may not relate to the reinforcement corrosion probability and a simple comparison of the corrosion
potential data with the ASTM C876 Standard on steel reinforcement corrosion probability could be meaningless and not give reliable informations because of environment factors as oxygen concentration, chloride content, concrete resistance. Therefore this paper explains the risk of corrosion assessment in reinforced concrete
structure and how many factors can affect the reliability of the corrosion potential data.
KEYWORDs : steel reinforcement, corrosion potential, oxygen, chloride, concrete resistance
AUTHORs : 정진아†

Page : 140 - 147 DOWNLOAD
캐비테이션 특성에 미치는 알루미늄 합금의 양극 산화 용액 온도의 영향
The commercialization of aluminum had been delayed than other metals because of its high oxygen affinity. Anodizing is a process in which oxide film is formed on the surface of a valve metal in an electrolyte solution by anodic oxidation reaction. Aluminum has thin oxide film on surface but the oxide film is inhomogeneous having a thickness only in the range of several nanometers. Anodizing process increases
the thickness of the oxide film significantly. In this study, porous type oxide film was produced on the surface of aluminum in sulfuric acid as a function of electrolyte temperature, and the optimum condition were determined for anodizing film to exhibit excellent cavitation resistance in seawater environment. The result revealed that the oxide film formed at 10 ℃ represented the highest cavitation resistance, while
the oxide film formed at 15 ℃ showed the lowest resistance to cavitation in spite of its high hardness.
KEYWORDs : aluminum, anodizing, oxide film, cavitation, seawater
AUTHORs : 이승준·이정형, 김성종†

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분말야금법과 주조법으로 제조한 자동차 터보차져강의 고온산화
Turbocharger steels were manufactured by the powder metallurgical and casting method. They consisted primarily of a large amount of γ-Fe, a small amount of α-Fe, and fine Nb6C5 precipitates. The casting method was better than the powder metallurgical method, because a sound matrix with little oxides were obtained. When turbocharger steels were oxidized at 900 ℃ for 50 h, Mn₂VO₂and (Mn,Si)-oxides were formed along grain boundaries, while Mn2O3 and CrMn₂O₂ were formed intragranularly. Fe, Nb, and Ni were depleted in the oxide scale.
KEYWORDs : turbocharger, oxidation, powder metallurgy, casting
AUTHORs : 박순용·이동복†

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Effect of Si on Corrosion of Fe-Cr and Fe-Cr-Ni Alloys in wet CO₂Gas
Model alloys Fe-9Cr, Fe-20Cr and Fe-20Cr-20Ni (wt. %) with 0.1 and 0.2 % Si were exposed to Ar-20CO₂-20H₂O gas at 818 oC. The undoped alloys formed a thick iron-rich oxide scale. The additions of Si reduced scaling rates of Fe-9Cr to some extent but significantly suppressed the formation of iron oxide scales on Fe-20Cr
and Fe-20Cr-20Ni. Carburisation also occurred in all undoped alloys, but not in Si-containing Fe-20Cr and Fe-20Cr-20Ni. Protection against carburisation was a result of the formation of an inner scale layer of silica.
KEYWORDs : steel, silicon, high temperature corrosion
AUTHORs : T. D. Nguyen, J. Zhang, and D. J. Young†

Page : 120 - 126 DOWNLOAD
Effects of Induction Heat Bending Process on Microstructure and Corrosion Properties of ASME SA312 Gr.TP304 Stainless Steel Pipes
The usage of bending products recently have increased since many industries such as automobile, aerospace, shipbuilding, and chemical plants need the application of pipings. Bending process is one of the inevitable steps to fabricate the facilities. Induction heat bending is composed of compressive bending process by local heating and cooling. This work focused on the effect of induction heat bending process on the properties of ASME SA312 Gr. TP304 stainless steel pipes. Tests were performed for base metal and bended area including extrados, intrados, crown up, and down parts. Microstructure was analyzed using an optical microscope
and SEM. In order to determine intergranular corrosion resistance, Double Loop Electrochemical Potentiokinetic Reactivation (DL-EPR) test and ASTM A262 practice A and C tests were done. Every specimen revealed non-metallic inclusion free under the criteria of 1.5i of the standard and the induction heat bending process
did not affect the non-metallic inclusion in the alloys. Also, all the bended specimens had finer grain size than ASTM grain size number 5 corresponding to the grain sizes of the base metal and thus the grain size of the pipe bended by induction heat bending process is acceptable. Hardness of transition start, bend,
and transition end areas of ASME SA312 TP304 stainless steel was a little higher than that of base metal. Intergranular corrosion behavior was determined by ASTM A262 practice A and C and DL-EPR test, and respectively step structure, corrosion rate under 0.3 mm/y, and Degree of Sensitization (DOS) of 0.001 ~ 0.075 %
were obtained. That is, the induction heat bending process didn’t affect the intergranular corrosion behavior of ASME SA312 TP304 stainless steel.
KEYWORDs : induction heat bending, 304 stainless steel, microstructure, intergranular corrosion
AUTHORs : Nam In Kim, Young Sik Kim†, Kyung Soo Kim, Hyun Young Chang,Heung Bae Park, and Gi Ho Sung

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Effects of Hydrogen on the PWSCC Initiation Behaviours of Alloy 182 Weld in PWR Environments
Alloy 82/182 weld metals had been extensively used in joining the components of the PWR primary system. Unfortunately, there have been a number of incidents of cracking caused by PWSCC in Alloy 82/182 welds during the operation of PWR worldwide. To mitigate PWSCC, optimization of water-chemistry conditions,
especially dissolved hydrogen (DH) and Zn contents, is considered as the most promising and effective remedial method. In this study, the PWSCC behaviours of Alloy 182 weld were investigated in simulated PWR environments with various DH content. Both in-situ and ex-situ oxide characterizations as well as PWSCC initiation tests were performed. The results showed that PWSCC crack initiation time was shortest in PWR water (DH: 30 cc/kg). Also, high stress reduced crack initiation time. Oxide layer showed multi-layered structures consisted of the outer needle-like Ni-rich oxide layer, Fe-rich crystalline oxide, and inner Cr-rich
inner oxide layers, which was not altered by the level of applied stress. To analyse the multi-layer structure of oxides, EIS measurement were fitted into an equivalent circuit model. Further analyses including TEM and EDS are underway to verify appropriateness of the equivalent circuit model.
KEYWORDs : PWSCC, oxide, in-situ EIS, initiation, alloy 182
AUTHORs : H.-S. Kim, J.-D. Hong, J. Lee, O. S. Gokul, and C. Jang†

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