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인공 수돗물 분위기에서 저탄소강의 부식특성에 미치는 합금원소(Cr, Co, W, Cu, Ni, Ca)의 영향에 관한 연구
심재주,최윤석,김정구 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.9
This paper presents the corrosion behavior of the low alloy steel contained alloying elements such as Cr, Co, W, Cu, Ni and Ca in synthetic tap water using potentiodynamic polarization tests, electrochemical impedance spectroscopy (EIS), XPS and EPMA. Potentiodynamic poalrization curves indicated that all the specimens had active corrosion behavior. Corrosion rate tended to reduce as the result of the alloying. Also, EIS test results showed that the more the content of element, the larger the polarization resistance. It can be seen that these results were caused from the formation of a coherent, protective film contained alloying elements. Actually, XPS results showed that Cr, Cu, and Ca were formed as protective metal oxides at the surface of rust film under the stagnant condition. The results of EPMA indicated that Cr, Cu, and Ca were distributed densely at the inner layer of the rust film, while Co, W, and Ni were distributed at the whole layer under the flow condition. Consequently, alloying elements improved corrosion resistance of low alloy steel in synthetic tap water. Especially, Cr, Cu, Ni, and Ca-containing specimen had the lowest corrosion rate due to the inner rust film formation during the initial stage of corrosion, which suggested a potential substitute for carbon steel in potable water system.
심재주,신동호,최윤석,김정구,유승재 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.12
The corrosion behavior of copper in neutral aerated synthetic tap water was investigated using electrochemical methods, SEM and XPS. All potentiodynamic polarization curves showed active corrosion behavior, and the corrosion rate was more sensitive to flow velocity than Cl^(-) ion concentration and temperature. The result of potentiostatic test indicated that the current density decreased with increasing time regardless of Cl^(-) ion concentration and temperature in stagnant condition because copper compounds were formed uniformly on the surface. The EIS plot was changed from two time constants to three time constants with the formation of Cu₂O, and the charge transfer resistance (R_(ct)) was very large and increased with increasing immersion time. From all results, copper had good corrosion resistance in this potable water system.
인공 해수분위기에서 저탄소강의 부식특성에 미치는 합금원소 Cr, Co 및 W의 효과
심재주,유승재,최윤석,김정구,유장용 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.12
The aqueous corrosion characteristics of 1% Cr-steel alloyed with small amounts of Co and W, in synthetic seawater was studied by using immersion weight-loss tests, electrochemical corrosion tests (potentiodynamic test and electrochemical impedance spectroscopy (EIS) measurements) and analytical techniques. 1% Cr steels containing Co or W from 0.2 to 0.4 wt.% showed higher corrosion resistance than the 1% Cr steel in the immersion and potentiodynamic tests. EIS measurements showed that the Nyquist plot presented one time constant. Furthermore, the Co- and W-bearing steels present higher Rp values than the 1% Cr steel through all the test period. The better corrosion resistance of the Co-and W-bearing steels is attributed to protectiveness of the surface layer. The corrosion products were examined using electron probe microanalysis (EPMA) and X-ray photoelectron spectroscopy (XPS). The results of EPMA indicated that Cr was concentrated in the inner region of the rust layer, while Co and W were distributed all over the rust layer. XPS results showed that Co existed as a trivalent oxide in the rust layer and W in the rust appeared in the form of a WO₄ compound.
희생양극을 이용한 자동차 소음기의 음극방식에 관한 연구
신동호,심재주,최윤석,김정구 대한금속재료학회 2004 대한금속·재료학회지 Vol.42 No.12
In order to apply a sacrificial anode cathodic protection system for automotive muffler materials, determination of reliable sacrificial anode and its protection ability were evaluated by laboratory tests in synthetic condensed water. Three kinds of sacrificial anodes were selected: aluminum (AI), zinc (Zn) and magnesium (Mg), and the muffler materials were Al-coated steel and uncoated steel. The corrosion behavior in synthetic condensed water for the muffler materials and sacrificial anodes was investigated by potentiodynamic tests. The cathodic protection ability was evaluated by galvanic corrosion test and weight-loss test. The results of the potentiodynamic test indicated that Al was less suitable for sacrificial anode because it became passive. Mg was also unqualified due to the high dissolution rate. However, Zn was adequate for sacrificial anode because of its low dissolution rate, high stability and suitable potential difference. Results of weight-loss test demonstrated that the corrosion rate of Al-coated steel was reduced from 0.028 to 0.018 mm/year, and that of uncoated steel was 0.08 to 0.002 mm/year by coupling with Zn anode. In addition, the proper area ratio of anode to cathode was 1 : 10. From these results, it can be concluded that Zn anode can protect both the Al-coating with passivation, and steel substrate with low dissolution rate. (Received January 8, 2004)
Cr, Co, Cu, Ni와 Ca의 첨가에 따른 지하매설배관의 전기화학적 특성에 관한 연구
최윤석,신동호,심재주,김정구 대한금속재료학회 2005 대한금속·재료학회지 Vol.43 No.1
Aqueous corrosion characteristics of low carbon steel with small amounts of Cr, Co, Cu, Ni and Ca, in synthetic groundwater was studied by electrochemical corrosion tests (potentiodynamic test and electrochemical impedance spectroscopy (EIS) measurements) and analytical techniques. Neither carbon steel nor newly alloyed steels showed passive behavior in this synthetic groundwater. Newly alloyed steels, containing Cr-Co, Cr-Cu-Ni and Cr-Cu-Ni-Ca showed higher corrosion resistance than carbon steel in the potentiodynamic tests. EIS measurements showed that the Nyquist plot presented two time constants. The high frequency resistance component (R_(rsut)) and low frequency resistance component (R_(et)) were affected by the alloying elements. The polarization resistance (RP= R_(et) +Ra) of steels could be clearly ranked as Cr-Cu-Ni-Ca steel >> Cr-Cu-Ni steel > Cr-Co steel > carbon steel. Results of surface analyses (XPS and EPMA) showed that Cr and Cu were concentrated in the inner region of rust. However, Co and Ni were uniformly distributed all over the rust layer. These alloying elements improved corrosion resistance of low alloy steel in synthetic groundwater. Especially, Cr-Cu-Ni-Ca steel had the lowest corrosion rate due to the inner rust film formation during the initial stage of corrosion, which suggested a potential for substituting carbon steel in soil environment (Received October 29, 2004)