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| DYNAMIC ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY CHARACTERISTICS OF SENSITIZED STEEL 00Cr12Ti |
| YAN Ruixia, DU Cuiwei, LIU Zhiyong, LI Xiaogang |
| Corrosion and Protection Center, University of Science and Technology Beijing; Key Laboratory for Corrosion and Protection, Beijing 100083 |
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Abstract In this paper, double-loop electrochemical potentiokinetic reactivation (DL-EPR) and dynamic electrochemical impedance spectroscopy (DEIS) by forward and reverse potential scan have been used to investigate sensitized ferritic stainless steel 00Cr12Ti exposed to 0.1 mol/L H2SO4+0.0001 mol/L KSCN solution and fitted with proper equivalent circuits. The results indicated that the region distribution of DEIS is in accordance with that of DL-EPR, including activation region, transition region, passivation region and reactivation region. In the passivation region, the capacity loop shrunk at about 0.2 V, and the real part of EIS curve at the low frequency decreased even became negative. The main reason is that the passive film is not complete and a part of fresh surface is exposed to the solution. In the reactivation region, before occurrence of intergranular corrosion, at about 0.2 V, the capacity loop decreased dramatically, and then gradually increased. At the low frequency the EIS displays a capacitive loop with negative resistance, this implies that the passive film suffers rupture and repair due to depletion of Cr at the grain boundary. An inductive loop which is ascribed to the adsorption of intermediate product on the electrode surface indicates that the diffusion process of the intermediate product predominated the corrosion reaction. The degree of sensitivity (DOS) expressed by the ratio of the reciprocal of the minimum Rct in the reactivation region to activation region on DEIS is the same as the DOS from DL-EPR.
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Received: 03 September 2010
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Corresponding Authors:
DU Cuiwei
E-mail: ducuiwei@yahoo.com
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