A Study of the Behavior of Bromide in Artificial Pits Using in Situ X-Ray Microprobe Analysis Page: 1 of 11
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A STUDY OF THE BEHAVIOR OF BROMIDE IN ARTIFICIAL PITS
USING IN SITU X-RAY MICROPROBE ANALYSIS
H. S. Isaacs+ and M. Kaneko'
+ Department of Applied Science,
Brookhaven National Laboratory, Upton NY 11973, USA..
*Nippon Steel Corp.,
2-6-3 Otemachi Chiyoda-Ku,
Tokyo 100-71, Japan.
ABSTRACT
An in situ x-ray microprobe analysis of Type 316 stainless steel artificial
pits has been carried out with bromide/chloride solution. A high intensity 8
pm diameter polychromatic x-ray beam was scanned across the
steel/solution interface within the artificial pit. The resulting x-ray
fluorescence was analyzed using an energy dispersive x-ray detector. In
contrast to the light CI atom, Br could be detected, making it possible to
monitor the behavior of halides in the artificial pits and in the salt layer at the
interface. It was found that Br was more active than Cl. At high potentials,
elemental Br was produced as an oxidation product, whereas without added
bromide, chloride only formed a salt layer. Br also concentrated at the
salt/steel interface at potentials below where it was oxidized.
INTRODUCTION
Major changes in solution composition occurs when pits and pores are produced. It is
the purpose of this paper is to describe an in situ x-ray fluorescence technique for solution
analysis that has been used to measure changes taking place during pitting of stainless
steels.(1,2) The technique has many similarities to scanning electron microprobe analysis,
but uses x-rays rather than electrons, to excite the elements. The particular advantage of the
technique was the in situ electrochemical control maintained during measurements. The
technique offers a method for determining, in detail, the concentration or depletion of
3-. elements at the metal/solution interface with a sensitivity difficult to achieve using other
techniques.
X-ray fluorescence has been used for many decades. (3,4) With the advent of light
CZ) sources and high intensity x-rays, collimated beams, micrometers in size, have been
C developed for the spatial resolution of elemental distributions.(5) In this electrochemical
(3) study of artificial pits, bromide is introduced to test if it could be used to trace the behavior
3) of chloride ions. CI is a relatively light element with a low x-ray florescence energy that is
too weak to penetrate about 0.25 mm of plastic used for windows in the cell construction.
(1,2) This work demonstrated that there were limitations in attempting to substitute Br for
Cl under conditions associated with pitting.
There have been few direct investigations of the solution in pits and cracks mainly
owing to difficulties in analyzing the small volumes of solution involved (1,2,6-9).
Consequently, few models take into consideration the importance of the solution chemistry
DISTR3BUT1ONV OF ThI D UMN '.AaF '
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Isaacs, H. S. & Kaneko, M. A Study of the Behavior of Bromide in Artificial Pits Using in Situ X-Ray Microprobe Analysis, report, December 31, 1997; Upton, New York. (https://digital.library.unt.edu/ark:/67531/metadc710479/m1/1/: accessed April 19, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.