This chapter presents a study in which the effects of lead (Pb) on passivity of Alloy 600 surface were investigated in mild acidic aqueous solutions at 90°C using polarization, electrochemical impedance spectroscopy (EIS), Auger electron spectroscopy (AES), and X-ray photoelectron spectroscopy (XPS). The tests were performed in a three electrode cell, which was purged with high-purity argon gas during the test, and the temperature was controlled at 90±2o C. A Gamry PC4/750 potentiostat, Solatron 1287 potentiostat, and a Solatron 1252A frequency response analyzer were used for electrochemical testing. The polarization curves were performed at a scan rate of 0.1 mV/sec, from open circuit potential (OCP) to +0.4 V/SHE in the anodic direction and from OCP to -0.6 V/SHE in the cathodic direction. The results indicate that Alloy 600 surface consists of an inner oxide layer and outer hydroxide layer, containing Cr3+ and Ni2+. Pb2+ inhibits the oxidation of Ni, and consequently, the growth of a Ni oxide layer is retarded. In addition, the incorporation of Pb2+ into Cr oxide enhances its electronic conductivity by increasing the concentration of the electron holes.
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The submitted manuscript has been created by the University of Chicago as Operator of Argonne National Laboratory (“Argonne”) under Contract No. W-31-109-ENG-38 with the U.S. Department of Energy. The U.S. Government retains for itself, and others acting on its behalf, a paid-up, nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government
The AES and XPS were performed at the Center for Microanalysis of Materials, University of Illinois, which is partially supported by the U.S. Department of Energy under grant DEFG02-91-ER45439.
This work was performed at Argonne National Laboratory, with support by the Division of Engineering Technology, Office of Nuclear Regulatory Research, U.S. Nuclear Regulator Commission. Argonne is operated by the University of Chicago for the Department of Energy under contract W-31-109-ENG-38.