GB843426A - Surface treatment of articles composed of an aluminium base alloy - Google Patents

Abstract

A finished or semi-finished article composed of an Al-base alloy containing 0.1-15% Mg is coated with an organic ammonium fluoroborate which yields boron trifluoride when heated to a temperature between 400 DEG F. and 750 DEG F., and heated to a temperature between 400 DEG and 750 DEG F. for a time sufficiently long to cause disappearance of the fluoroborate and the formation of a protectve film on the surface of the article. The Al-base alloy may also contain one or more of Cu 0.1-12%, Si 0.25-14%, Zn 0.1-20% and Mn 0.1-3%, together with not more than 3% in all of one or more of Cr 0.05-0.5%, Ti 0.01-0.5%, Ni 0.25-2.5%, B 0.01-0.5%, Be 0.002-2%, Mo 0.1-0.5%, Zr 0.1-0.5%, Ta 0.1-0.5%, Nb 0.1-0.5% and Co 0.1-0.5%: specific examples are given of the alloy. The fluoroborate may be di-n-butyl ammonium tetrafluoroborate, n-octadecyl N,N,N-trimethyl ammonium tetrafluoroborate or di-n-amyl ammonium tetrafluoroborate, and may be applied to the article in solution (aqueous or alcoholic, with wetting or other surface-active agents if desired), or in a molten state. The article may subsequently be de-gassed by heating at a temperature above 750 DEG F. but below the temperature of incipient fusion. Specification 494,274 and U.S.A. Specification 2,379,467 is referred to.