Influence of aeration on the passivation characteristics of AS/NZS 3679.1-300 mild steel in high-ternperature Bayer liquor under conditions of disturbed flow

Kear, G. and Bremhorst, K. (2008) Influence of aeration on the passivation characteristics of AS/NZS 3679.1-300 mild steel in high-ternperature Bayer liquor under conditions of disturbed flow. Corrosion, 64 4: 289-300. doi:10.5006/1.3278473


Author Kear, G.
Bremhorst, K.
Title Influence of aeration on the passivation characteristics of AS/NZS 3679.1-300 mild steel in high-ternperature Bayer liquor under conditions of disturbed flow
Journal name Corrosion   Check publisher's open access policy
ISSN 0010-9312
Publication date 2008-04-01
Year available 2008
Sub-type Article (original research)
DOI 10.5006/1.3278473
Open Access Status
Volume 64
Issue 4
Start page 289
End page 300
Total pages 11
Editor I. Perry
Place of publication Houston, Texas, USA
Publisher NACE International
Language eng
Subject C1
0913 Mechanical Engineering
970102 Expanding Knowledge in the Physical Sciences
Abstract The flow-enhanced corrosion of mild steel has been examined in high-temperature spent Bayer liquor as a function of Reynolds number, fluid flow disturbance, and electrolyte aeration. ne electrochemical characteristics of the steel in this electrolyte was derived using a high-pressure nickel flow loop at 160 degrees C (total gauge pressure = 0. 7 MPa to 0.9 MPa). The influence of both a sudden pipe expansion and a pipe contraction on both corrosion rate and polarization behavior was quantified. Considering the mechanism of the corrosion reaction, electrolyte mass transfer did not directly control the electrochemical rates of either the cathodic or anodic currents at the corrosion potential. It is concluded that chemical modification and/or dissolution/erosion of passivating layers may have a strong influence over the metal loss of the steel observed in some alumina plants. Aeration of the liquor was found to be a significant factor regarding passivation rates and the corrosion characteristics of acid-treated steel, and it caused an overall increase in the rate of active and. passive steel dissolution relative to the deoxygenated state for all but one electrode. However, the time to passivation was relatively low at high fluid velocities (Re congruent to 141,500), which led to a 27016 to 509,6 reduction in metal loss over a caustic exposure time of 19 h. At low velocities (Re congruent to 50,900), time to passivation in the aerated liquor was also lowered, but not to the same order as that observed in the high-velocity area. Therefore, as a result of elevated reaction rates in the presence of oxygen, total corrosive losses over this short operating period were up to 37%, higher than that of the deoxygenated electrolyte. The results were essentially independent of the level off low disturbance.
Keyword Bayer liquor
caustic
disturbed flow
erosion-corrosion
flow-affected corrosion
mass transfer
pipe flow
Q-Index Code C1
Q-Index Status Confirmed Code

Document type: Journal Article
Sub-type: Article (original research)
Collections: 2009 Higher Education Research Data Collection
School of Mechanical & Mining Engineering Publications
 
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Created: Thu, 09 Apr 2009, 20:37:45 EST by Rose Clements on behalf of School of Mechanical and Mining Engineering