EFFECT OF AMBIENT VACUUM PRESSURE ON THE CORROSION PROPERTIES OF PUREIRON FILMS FORMED BY THE ION-BEAM DEPOSITION METHOD

High purity iron films deposited on Si substrates by the low-energy, m ass-separated ion beam deposition (IBD) method showed the highest corr osion resistance against NaCl solution than any other iron materials. The corrosion properties of the films depend on the ambient vacuum con ditions during film formation. High pressure surroundings seem to brin g gaseous compounds into the films, which make the surfaces unstable o wing to a high density of defects in the films. Surface observations b y transmission electron microscopy indicate the presence of a stable i ron oxide layer on the IBD iron film which had formed under suitable v acuum conditions. The presence of fewer defects in IBD iron film seems to be a prerequisite of this protective oxide layer. (C) 1998 Elsevie r Science S.A. All rights reserved.