"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.
Straumanis, Martin E., 1898-1973
O'Keefe, T. J. (Thomas J.)
James, William Joseph
Materials Science and Engineering
M.S. in Metallurgical Engineering
United States. Office of Naval Research
Texaco Oil Company
University of Missouri at Rolla
x, 113 pages
© 1968 Barry L. Basden, All rights reserved.
Thesis - Open Access
Aluminum -- Dissolution -- Testing
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Link to Catalog Record
Basden, Barry L., "Influence of nobler metal salt additions upon the dissolution rate of aluminum in hydrofluoric acid" (1968). Masters Theses. 5218.