희생양극 하에서 알루미늄의 해수 부식 거동

김종수(Jongsoo Kim),김희산(Heesan Kim) 한국표면공학회 2006 한국표면공학회지 Vol.39 No.1

Al-Mg alloy, an open rack vaporizer(ORV) material was reported to be corroded in seawater environments though the ORV material was coupled to thermally sprayed Al-Zn alloy functioning a sacrificial anode. In addition, the corrosion behavior based on the calculated corrosion potential did not match the observed corrosion behavior. Hence, the goal of this study is to get better understanding on Al or Al-Mg alloy coupled to Al-Zn alloy and to provide the calculated corrosion potential representing the corrosion behavior of the ORV material by immersion test, electrochemical tests, and calculation of corrosion and galvanic potential. The corrosion potentials of Al and Al alloys also depended on alloying element as well as surface defects. The corrosion potentials of Al and Al-Mg alloy were changed with time. In the meantime, the corrosion potentials of Al-Zn alloys were not. The corrosion rates of Al-Zn alloys were exponentially increased with zinc contents. The phenomena were explained with the stability of passive film proved by passive current density depending on pH and confirmed by the model proposed by McCafferty. Dissimilar material crevice corrosion (DMCC) test shows that higher content of zinc caused Al-Mg alloy corroded more rapidly, which was due to the fact that higher corrosion rate of Al-Zn makes [H?] and [Cl?] more concentrated within pit solution to corrode Al-Mg alloy. Considering electrochemical reactions within pit as well as bulk in the calculation gives better prediction on the corrosion behavior of Al and Al-Mg alloy as well as the capability of Al-Zn alloy for corrosion protection.

Surface Oxide Films Affecting Metallic Corrosion

Sato, Norio 한국부식방식학회 2002 Corrosion Science and Technology Vol.31 No.4

Depending on their ionic and electronic properties, surface oxides influence metallic corrosion in aqueous solutions. The ion-selective property controls the transport of ions through the surface oxide, and the electronic property of the oxide influences the electrode potential of corroding metals. Anion-selective surface oxides accumulate corrosive anions accelerating the metallic corrosion, whereas cation-selective oxides inhibit the corrosion by removing corrosive hydrogen ions fi-om the metal surface. The presence of n-type surface oxides lowers the corrosion potential to decrease the metallic corrosion, while p-type surface oxides raise the corrosion potential accelerating the corrosion. Photoexcitation enhances these electronic effects of semiconducting surface oxides on the corrosion.

철근 콘크리트 구조물용 다기능 멀티센서의 부식 모니터링에 관한 연구: Part 1

진출국 ( Chung Kuk Jin ),정진아 ( A Jeong Jin ),경은진 ( Eun Jin Kyoung ) 한국부식방식학회(구 한국부식학회) 2012 Corrosion Science and Technology Vol.11 No.6

This study represents the result of corrosion monitoring on reinforced concrete specimens by means of multi-functional corrosion monitoring sensors. To confirm the effectiveness of the sensors eight different kinds of condition were adopted. Test factors were corrosion potential current corrosion rate resistivity and temperature which were monitored with the sensors. Through this study judging corrosion of steel in concrete with single corrosion factor such as corrosion potential was difficult because many other factors can have an influence on the reaction of corrosion. By using three different kinds of sensors it could enhance the accuracy of corrosion monitoring.

수종 임플랜트 금속의 내식성에 관한 전기화학적 연구

전진영,김영수,Jeon Jin-Young,Kim Yung-Soo 대한치과보철학회 1993 대한치과보철학회지 Vol.31 No.3

Titanium and its alloys are finding increasing use in medical devices and dental implants. The strong selling point of titanium is its resistance to the highly corrosive body fluids in which an implant must survive. This corrosion resistance is due to a tenacious passive oxide or film which exists on the metal's surface and renders it passive. Potentiodynamic polarization measurement is one of the most commonly used electro-chemical methods that have been applied to measure corrosion rates. And the potentiodynamic polarization test supplies detailed information such as open circuit, rupture, and passivation potential. Furthermore, it indicates the passive range and sensitivity to pitting corrosion. This study was designed to compare the corrosion resistance of the commonly used dental implant materials such as CP Ti, Ti-6A1-4V, Co-Cr-Mo alloy, and 316L stainless steel. And the effects of galvanic couples between titanium and the dental alloys were assessed for their useful-ness-as. materials for superstructure. The working electrode is the specimen , the reference electrode is a saturated calomel electrode (SCE), and the counter electrode is made of carbon. In $N_2-saturated$ 0.9% NaCl solutions, the potential scanning was performed starting from -800mV (SCE) and the scan rate was 1 mV/sec. At least three different polarization measurements were carried out for each material on separate specimen. The galvanic corrosion measurements were conducted in the zero-shunt ammeter with an implant supraconstruction surface ratio of 1:1. The contact current density was recorded over a 24-hour period. The results were as follows : 1. In potential-time curve, all specimens became increasingly more noble after immersion in the test solution and reached between -70mV and 50mV (SCE) respectively after 12 hours. 2. The Ti and Ti alloy in the saline solution were most resistant to corrosion. They showed the typical passive behavior which was exhibited over the entire experimental range. Therefore no breakdown potentials were observed. 3. Comparing the rupture potentials, Ti and Ti alloy had the high(:st value (because their break-down potentials were not observed in this study potential range ) followed by Co-Cr-Mo alloy and stainless steel (316L). So , the corrosion resistance of titanium was cecellent, Co-Cr-Mo alloy slightly inferior and stainless steel (316L) much less. 4. The contact current density sinks faster than any other galvanic couple in the case of Ti/gold alloy. 5. Ag-Pd alloy coupled with Ti yielded high current density in the early stage. Furthermore, Ti became anodic. 6. Ti/Ni-Cr alloy showed a relatively high galvanic current and a tendency to increase.

Influence of Corrosion Potential and Current Density on Polarization Curve Variations using Polycarbonate[III]

Park, Chil-Nam,Yang, Hyo-Kyung,Kim, Sun-Kyu,Kim, Myung-Sun,Cheong, Kyung-Hoon The Korean Environmental Sciences Society 2000 Environmental sciences Vol.4 No.1

In this study, experiments were carried out to measure the variations in the corrosion potential and current density of polarization curves using polycarbonate. The results were particularly examined to identify the influences affecting the corrosion potential including various conditions such as temperature, pH, catalytic enzyme, and salt. The lines representing the active anodic dissolution were only slightly shifted in the potential direction by temperature, pH, enzyme, and salt. The tafel slope for the anodic dissolution was determined based on the polarization effect with various conditions. The slope of the polarization curves describing the active-to-passive transition region were noticeably shifted in direction. Also, from the variation in the conditions, the optimum conditions were established for the most rapid transformation, including temperature, pH, corrosion rate, and resistance of corrosion potential. The second anodic current density peak and maximum passive current density were designated as the critical corrosion sensitivity(Ir/If). The value of Ir/If was then used in measuring the extent of the critical corrosion sensitivity of the polycarbonate. The potentiodynamic parameters of the corrosion were obtained using a Tafel plot.

치과 임플란트용 순 Ti의 접촉부식 거동

김교한,허만수,김형일,황운석,高田 雄京,奧野 攻 대한치과기재학회 1999 대한치과재료학회지 Vol.26 No.4

One of the fields in which titanium(Ti) is becoming increasingly valuable is the field of biomaterials. Ti had shown its good corrosion resistance, high strength to weight ratio, and compatibility with human tissues. Such applications of Ti in this area involve replacing stainless steel and cobalt-chromium alloy implant which are used in skull, shoulder joint, spine, and dental implant. In dental field, titanium has been used as dental implant, so it becomes necessary to examine and estimate the anti-corrosion ability of Ti and its alloys at the severe conditions such as crevice corrosion and galvanic corrosion. The purposes of this study was to examine the corrosion mechanisms of the pure Ti showing good corrosion resistance under an oral corrosion environment when it is coupled with dental casting Type Ⅱ and Type Ⅳ gold alloys. These coupling corrosion mechanisms were studied in three conditions. First was by measuring the resting potential of pure Ti, when it was uncoupled and coupled with Type Ⅱ and Type Ⅳ alloys. Second was by measuring anode polarization behavior of pure Ti, Type Ⅱ and Type Ⅳ alloys, and third was by detecting dissolved ions from the pure Ti, uncoupled and coupled with Type Ⅱ and Type Ⅳ gold alloys which were immersed in 0.9% NaCl solution for 7 days. The resting potential showed a low potential value at the initial stage but increasing into a high value (to 0.18 V) with time elapse and reached a stable value. On the contrary, the potentials of Type Ⅱ and Type Ⅳ gold alloys were in their values at the initial stage of immersion, then decreased with the time and reached stable values, being higher than the value of pure Ti. When pure Ti coupled with Type Ⅱ and Type Ⅳ gold alloys, the resting potential of coupled one was between the values of each one. When Type Ⅱ and Type Ⅳ gold alloys were coupled with pure Ti, there was an increase in Ag, Cu, and Zn. Also, Zn ions released the high potential precious metal alloys, compared to the uncoupled case. Ti ion was not detected at any cases of pure Ti or coupled with gold alloys. It was thought that one of the causes of the increase in Ag, Zn, and Cu ions when Ti was coupled with dental gold alloys was that Ag, Zn, and Cu ions were selectively dissoluted from the Ag rich regions around grain boundary and the casting defects. In conclusions, the results of this study suggest that the pure Ti was very stable when coupled with the gold alloys in oral cavity.

orrosion Mitigation Strategies for Ni-based Alloy in NaCl-MgCl2 Melts at 973 K

Younghwan Jeon,Hyeongjin Byeon,Yeojin Kim,Jaeyeong Park 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.1

A molten salt reactor (MSR) is a conceptual nuclear reactor that uses molten salt with liquid fuel as its primary coolant. Based on the thermophysical and neutronic properties, MSR has advantages such as high efficiency, safety, combustion of transuranic (TRU) elements, and availability of miniaturization and on-power refueling. Various research on MSR such as system development, neutronic analysis, material development, and molten salt property analysis has been conducted, but the biggest problem is the molten salt corrosion. The molten salt corrosion on structural materials can be explained by two processes; electrochemical and chemical reactions. The reduction of oxidative ions such as fuel and TRU elements is one of the major causes of molten salt corrosion. Contamination by humidity and oxygen is also known as the accelerating factor of molten salt corrosion. Also, molten salt corrosion behaviors on structural material deteriorate when dissimilar alloys are introduced in the molten salt system. Various techniques to mitigate molten salt corrosion in fluoride system has been developed, but these are not well-verified in chloride system. In this research, various methodologies to mitigate molten salt corrosion are studied. The corrosion behaviors of 80Ni-20Cr alloy in molten eutectic NaCl-MgCl2 salt at 973 K are analyzed with various applications such as salt purification, sacrificial metal injection, and salt redox potential control. Oxygen and water impurities that can accelerate molten salt corrosion have been removed by electrochemical and chemical methods; Applying the reduction potential for H+/H2 and oxidation potential for O2-/O2, introducing HCl and CCl4 gas, and introducing the metallic Cr and recovering the ionized Cr. Corrosion acceleration/deceleration effects were analyzed when introducing the reducing reagent such as Mg and Nb or oxidizing reagent such as metallic Mo and the effect of inert metallic element (W) was also investigated. The salt potential was controlled by applying the potential to the salt and adjusting the Eu3+/Eu2+ ratio.

Effects of Chloride and Crevice on Corrosion Resistance of Stainless Steels Buried in Soil within Seoul Metropolitan

현영민,Heesan Kim,김영호 대한금속·재료학회 2014 METALS AND MATERIALS International Vol.20 No.2

Field and laboratory tests were conducted to find the factors affecting corrosion of stainless steels in soil. During one-year exposure, corrosion occurred within a joint and on the surface of type 304 pipe with thejoint, which was buried at the site with a high chloride concentration of about 3680 ppm; however, corrosionwas not observed at any of the other sites independent of the stainless steel grade and the presence of joints. At some sites, a seasonal fluctuation of corrosion potential was observed in the soil though corrosion didnot occur. This observation may be due to the activity of sulfate reducing bacteria because a decrease ofcorrosion potential with the inoculated bacteria did not cause corrosion of stainless steels. These resultsindicate that both the level of chloride and the presence of crevices are the main factors affecting corrosionof stainless steels in soil but that the activity of bacteria is not. From measurements of pitting potential, aguideline for stainless steel use in soil is drawn as follows: Corrosion of stainless steels in soil occurs when thepitting potential of stainless steel under crevices in synthetic ground water that contains the same chlorideconcentration as the soil is less than the saddle potential. Finally, the guideline for stainless steels applicationswas provided in this paper according to this criterion.

Anti-corrosive Effects of Multi-Walled Carbon Nano Tube and Zinc Particle Shapes on Zinc Ethyl Silicate Coated Carbon Steel

( Jiman Jang ),( Minyoung Shon ),( Samtak Kwak ) 한국부식방식학회(구 한국부식학회) 2016 Corrosion Science and Technology Vol.15 No.1

Zinc ethyl silicate coatings containing multi walled carbon nanotubes (MWCNTs) were prepared, to which we added spherical and flake shaped zinc particles. The anti-corrosive effects of MWCNTs and zinc shapes on the zinc ethyl silicate coated carbon steel was examined, using electrochemical impedance spectroscopy and corrosion potential measurement. The results of EIS and corrosion potential measurement showed that the zinc ethyl silicate coated with flake shaped zinc particles and MWCNT showed lesser protection to corrosion. These outcomes were in agreement with previous results of corrosion potential and corrosion occurrence.

Affect of Corrosion Potential and Current Density on Polarization Curves Variations of Polyvinylchloride[II]

Park, Chil-Nam,Yang, Hyo-Kyung,Kim, Sun-Kyu The Korean Environmental Sciences Society 1999 Environmental sciences Vol.3 No.3

This study performed experiments for measuring corrosion potential and current density variations in the polarzation curves of polyvinylchloride. The results were examined to identify particular influences affectingthe corrosion potential such as temperature, pH, enzyme, and salt. The lines representing active anodic dissolution were only slightly shifted in the potential direction by temperature, pH, enzyme and salt. The Tafel slope for the anodic dissolution was determined using the polarization effect with varying conditions. The slope of the polarization curves describing the active-to-passive transition region was noticeably shifted in the potential direction. In addition, using the variation in conditions, the best temperature and pH were determined for the corrosion rate, and resistance of corrosion. The second anodic current density peak and maximum passive current density were designated as degraded(IP/I0). The value of IP/I0 was used in measuring the extent of the degradation of the polyvinychloride. The potentiodynamic parameters of the corrosion were obtained using a Tafel plot.