Generally, the test failed what it was intended
to show. It was hoped that the aluminium
that melted in rich nitrogen would show a
different oxidation level than that melted in
rich oxygen. But aluminium oxidizes so
rapidly that under the conditions in the test or
in the aircraft, it was and would be impossible
to tell the difference. Even in seawater,
there is sufficient oxygen to oxidize the
freshly exposed layers. If I remember my
elementary chemistry correctly, aluminium tends
to oxidize very rapidly to a thin layer of
aluminium oxide. The difference between it
and iron is that the aluminium layer remains
intact and retains roughly the same properties
as the non-oxide aluminium. It protects
the underlying layers, forming a barrier to
further oxidation. What we are used to
seeing on aluminium foil, etc., is actually
aluminium oxide. Iron works differently in
that we call the oxide layer rust, and it falls
off without protecting the underlying layer of
iron. It certainly was worth the effort to
do the test, but one cannot always be successful
in these endeavours.
However, a by-product of the tests was that AES
was used for some of the analysis and very high
levels of magnesium were found in the
environmental layer of the molten aluminium
drops. This matter was discussed on
00-05-25 in a meeting with TSB, and my notes for
that date apply. It was determined at that
time (having been suggested by Larry VANCE) that
the cause of the high levels was the
contaminated fin plate on which they were
dropped. What was not known at that time
and has never been mentioned, but what tends to
confirm the theory is that relatively high
levels of carbon were also found in the AES
readings. But there was no carbon present
to burn, as these were aluminium alloy coupons
from Boeing without paint or anything else
containing carbon. So I certainly feel
confident that the high magnesium readings were
from the contamination on the fin plate that had
been selected
from the crash debris.