|
Vol.43, No.1, 37 ~ 44, 2005
|
| Title |
| Effect of Cr, Co, Cu, Ni and Ca on the Electrochemical Behavior of Buried Pipeline |
| 최윤석 Yoon Seok Choi , 신동호 Dong Ho Shin , 심재주 Jae Joo Shim , 김정구 Jung Gu Kim |
|
|
|
| Abstract |
| 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) |
|
|
| Key Words |
| Aqueous environments, Carbon steel, Alloying effect, Rust Layer, EIS |
|
|
 |
|
