Author: Lloyd G. O.
Publisher: Maney Publishing
ISSN: 0007-0599
Source: British Corrosion Journal, Vol.12, Iss.3, 1977-01, pp. : 144-151
Disclaimer: Any content in publications that violate the sovereignty, the constitution or regulations of the PRC is not accepted or approved by CNPIEC.
Abstract
The oxide film formed at 600°c on iron-chromium alloys consists of a thin inner chromium-rich layer with a much thicker outer layer of Fe2 03. The Fe2O3 can be removed from stripped oxide films by etching with solutions of hydrochloric acid in methanol; about 90–95% of the iron is removed, but no chromium. Etching avoids the difficulties in characterising the films introduced by the Fe2O3, which confuses both electron microscopy and X-ray analysis. This technique yields information on the oxidation process which cannot be obtained by other means, and it is particularly useful with oxide features too thick to be characterised directly. Consideration of the kinetics of the etching process suggests that the main factor affecting the rate is the stoichiometry of the Fe2 03, so that etching also indicates changes in stoichiometry as oxidation proceeds. Initiation of etching shows some dependence on the chromium-rich oxide sheet, but the effects are short-lived. The mechanism is discussed with reference to published work on the pitting of stainless steels.
Related content
British Corrosion Journal, Vol. 15, Iss. 2, 1980-01 ,pp. :
Microstructural and corrosion aspects of alloy 690
British Corrosion Journal, Vol. 34, Iss. 3, 1999-03 ,pp. :