Wa. Badawy et al., Electrochemical behaviour and corrosion inhibition of Al, Al-6061 and Al-Cu in neutral aqueous solutions, CORROS SCI, 41(4), 1999, pp. 709-727
The electrochemical behaviour of Al and two of its widely used alloys, Al-6
061 and Al-Cu, was investigated in neutral solutions at pH 7. The corrosion
inhibition of these materials was studied in neutral solutions using sulph
ates, molybdates and dichromates as passivators. The effectiveness of dichr
omates as passivators for Al and its alloys in these solutions was discusse
d. X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy
(SEM) were used to explain the role of the passivating anion in the corrosi
on inhibition process. It was found that Cr and Mo are incorporated in the
barrier film on Al or its alloys after immersion in neutral solutions conta
ining these anions. Sulphate ions are adsorbed on the barrier film surface
or present in the film in a very low concentration compared to dichromates
and molybdates. The inhibition efficiency increases as the concentration of
the passivating anion in the solution increases. Scanning electron microsc
opy (SEM) has shown that the Al-Cu ahoy has remarkable flawed regions which
are due to the presence of Cu on the alloy surface, as was confirmed by XP
S. The flawed regions completely disappear after immersion in solutions con
taining dichromates and partially disappear after immersion in solutions co
ntaining molybdates. (C) 1999 Elsevier Science Ltd. All rights reserved.