Masters Theses

Abstract

"The rate of dissolution of aluminum in 2N HF upon the addition of nobler metallic salts was studied. Aluminum corrodes in HF due to the acid's ability to dissolve the protective oxide present on the surface. Rates were measured by the hydrogen evolution method. Salt additions of AgN0₃, CuSO₄, HAuC₄, and PtCl₄ to aluminum dissolving in 2N HF resulted in the electroless deposition of more or less coherent metals (from the salts mentioned) on the aluminum surface. The dissolution rate initially decreased in all of the cases and was attributed to the "blanketing effect" of the deposits. Ensuing increases of rate after the initial decrease was probably due to the uncovering of local cathodes beneath the inhibiting deposit. All experiments involving PtCl₄ were carried out in nitrogen atmospheres which caused a greater dissolution rate due to the absence of strongly protective layers. Additions of the salt solutions of NiCl₂, FeS0₄, and CuS0₄ gave similar rate fluctuations, but no visible deposit. It was suspected that thin invisible layers electrolessly deposited were present on the aluminum surface. Qualitative testing was performed in many of the cases to observe formation of various precipitates. Electropotential measurements of aluminum showed that the anodic potential increased in the salt solutions mentioned above and thus supported the measured rate decreases. Microhardness tests were performed and showed harder surfaces on the aluminum dissolving in HF with added nobler metal salts, because of Ag, Ni and Co layers present on it. These facts substantiated the theory of thin layers electrolessly deposited on the aluminum surface which inhibited the rate of dissolution. Electron microscopy showed a difference in the etching behavior of a sample of aluminum etched in HF and an aluminum sample etched in HG in the presence of NiCl₂"--Abstract, page ii-iii.

Advisor(s)

Straumanis, Martin E., 1898-1973

Committee Member(s)

O'Keefe, T. J. (Thomas J.)
James, William Joseph

Department(s)

Materials Science and Engineering

Degree Name

M.S. in Metallurgical Engineering

Sponsor(s)

United States. Office of Naval Research
Texaco Oil Company

Publisher

University of Missouri at Rolla

Publication Date

1968

Pagination

x, 113 pages

Note about bibliography

Includes bibliographical references (page 42).

Rights

© 1968 Barry L. Basden, All rights reserved.

Document Type

Thesis - Open Access

File Type

text

Language

English

Subject Headings

Aluminum -- Dissolution -- Testing
Aluminum
Precious metals

Thesis Number

T 2080

Print OCLC #

5994889

Electronic OCLC #

802284675

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