Surface Film of Aluminium

Abstract

IT is generally believed that the surface of aluminium is normally covered with a thin layer of aluminium oxide or hydroxide, and that the metal possesses the property of forming this film on freshly cleaned surfaces. Bengough and Hudson (Jour. Inst. Metals, 21, P. 143) state, “the metal is normally covered with a layer of oxide,” and Seligman and Williams(Jour. Inst. Metals, 23, P. 169), “It is generally assumed that aluminium exposed to air is covered by a film of oxide or hydroxide which preventsthe complete oxidation of the metal. The film is invisible and, so far as the writers are aware, no direct evidence of its existence on aluminium ordinarily treated has been adduced.”