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    Volume 5, Issue 1

    Investigation of Mott–Schottky Analysis Test Parameters to Study the Semiconductive Properties of Passive Films of Carbon Steel in Highly Alkaline Environments

    (Received 2 September 2015; accepted 18 February 2016)

    Published Online: 18 March 2016

    CODEN: ACEMF9

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    Abstract

    A testing methodology for using Mott–Schottky (M-S) analysis to study the semiconductive properties of passive films that form on carbon steel in simulated concrete pores solutions (pH > 12.5) is presented. The development of the methodology includes determining the proper M-S potential sweep range, rate, and frequency for the passive steel, which were found to be −0.5 to 0.5 V, 18 mV/s, and 1000 Hz, respectively. The methodology was then applied to steel rebar in a saturated calcium hydroxide passivating solution (pH 12.6) to simulate the highly alkaline environments seen in concrete. Potentiostatically formed passive film was different from the film formed under open-circuit conditions. The passive film on steel rebar was found to be n-type with two discrete donor species. A donor density on the order of 1021 cm−3, a flatband potential of −0.53 V, and a maximum space charge layer thickness of 0.4 nm at full passivation were reported.

    Author Information:

    Williamson, J.
    Graduate Student, Oregon State Univ., Materials Science Program, Corvallis, OR

    Isgor, O. B.
    Associate Professor, Oregon State Univ., School of Civil and Construction Engineering, and Materials Science Program, Corvallis, OR


    Stock #: ACEM20150031

    ISSN:2165-3984

    DOI: 10.1520/ACEM20150031

    Author
    Title Investigation of Mott–Schottky Analysis Test Parameters to Study the Semiconductive Properties of Passive Films of Carbon Steel in Highly Alkaline Environments
    Symposium ,
    Committee G01