Mansfield, C. and Chen, F. and Breslin, Carmel B. and Dull, D. (1998) Sealing of Anodised Aluminium Alloys with Rare Earth Metal Salt Solutions. Journal of the Electrochemical Society, 145 (8). pp. 2792-2798. ISSN 0013-4651

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Abstract

Boric‐sulfuric acid anodized (BSAA) aluminum alloys have been sealed in hot solutions of cerium or yttrium salts. For comparison, sealing has also been performed in the presently used dilute chromate solution, boiling water, and a cold nickel fluoride solution. The corrosion resistance of the sealed BSAA Al alloys Al 2024, Al 6061, and Al 7075 has been evaluated by recording impedance spectra during exposure in 0.5 N NaCl for 7 days. Shorter or longer exposure times have also been used depending on the corrosion resistance obtained by different sealing processes. From the impedance spectra the time dependence of the pore resistance, R po, and the specific admittance, A s, has been determined. At the end of the exposure the pitted area, A pit, was calculated. The relationship between A s and R po has been evaluated. Two different sealing mechanisms were detected. For sealing in dilute chromate the pores in the outer oxide layer stayed open, while for hot water sealing or sealing in cold nickel fluoride the pores were closed by an oxide/hydroxide. Sealing of BSAA Al alloys in cerium or yttrium salt solutions occurred according to one of these two mechanisms depending on alloy type and solution composition. Based on the experimental values of R po, A s, and A pit it was concluded that sealing in cerium nitrate and yttrium sulfate solutions provided corrosion resistance similar to that of chromate‐sealed BSAA Al alloys.

Item Type:	Article
Keywords:	aluminium alloys; anodised layers; surface treatment; corrosion resistance; electric impedance;
Academic Unit:	Faculty of Science and Engineering > Chemistry
Item ID:	7949
Identification Number:	https://doi.org/10.1149/1.1838716
Depositing User:	Dr. Carmel Breslin
Date Deposited:	21 Feb 2017 16:16
Journal or Publication Title:	Journal of the Electrochemical Society
Publisher:	Electrochemical Society
Refereed:	Yes
Funders:	Boeing Information, Space and Defence Systems
URI:	http://jes.ecsdl.org
Use Licence:	This item is available under a Creative Commons Attribution Non Commercial Share Alike Licence (CC BY-NC-SA). Details of this licence are available here

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