Patch and whole of surface mass-transfer rate measurements on a stepped rotating cylinder electrode

Bremhorst, K., Kear, G., Keating, A. J. and Huang, S. H. (2005) Patch and whole of surface mass-transfer rate measurements on a stepped rotating cylinder electrode. Corrosion, 61 10: 968-975. doi:10.5006/1.3280897


Author Bremhorst, K.
Kear, G.
Keating, A. J.
Huang, S. H.
Title Patch and whole of surface mass-transfer rate measurements on a stepped rotating cylinder electrode
Journal name Corrosion   Check publisher's open access policy
ISSN 0010-9312
1938-159X
Publication date 2005-10
Sub-type Article (original research)
DOI 10.5006/1.3280897
Volume 61
Issue 10
Start page 968
End page 975
Total pages 8
Place of publication Houston, TX, United States
Publisher NACE international
Language eng
Subject 291803 Turbulent Flows
780103 Chemical sciences
Abstract A recently developed whole of surface electroplating technique was used to obtain mass-transfer rates in the separated flow region of a stepped rotating cylinder electrode. These data are compared with previously reported mass-transfer rates obtained with a patch electrode. It was found that the two methods yield different results, where at lower Reynolds numbers, the mass-transfer rate enhancement was noticeably higher for the whole of the surface electrode than for the patch electrode. The location of the peak mass transfer behind the step, as measured with a patch electrode, was reported to be independent of the Reynolds number in previous studies, whereas the whole of the surface electrode shows a definite Reynolds number dependence. Large eddy simulation results for the recirculating region behind a step are used in this work to show that this difference in behavior is related to the existence of a much thinner fluid layer at the wall for which the velocity is a linear junction of distance from the wall. Consequently, the diffusion layer no longer lies well within a laminar sublayer. It is concluded that the patch electrode responds to the wall shear stress for smooth wall flow as well as for the disturbed flow region behind the step. When the whole of the surface is electro-active, the response is to mass transfer even when this is not a sole function of wall shear stress. The results demonstrate that the choice of the mass-transfer measurement technique in corrosion studies can have a significant effect on the results obtained from empirical data.
Keyword Corrosion rate
Diffusion-limited current
Erosion-corrosion
Mass transfer
Rotating electrode
Turbulence
Velocity
Backward-facing Step
Turbulent-flow
Erosion-corrosion
Disturbed Flow
Heat-transfer
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status UQ

 
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Created: Wed, 15 Aug 2007, 05:52:13 EST