It's water, *air* and steel. Rust is formally known as oxidisation, i.e.
from the oxygen in air. Not sure about steel but I know wooden fence posts,
for example, usually only rot at ground level. Not further below ground
where it is permanently wet and there is no air, and not above ground where
it spends much more time dry than wet from rain. In Henry VIII's day ships
timbers were buried in rivers and mud for many years to 'pickle' them which
makes them largely impervious to rotting at sea. Dig up a rotted fence post
stump and you will see what I mean.
As far as steel goes I did read many years ago that one quality motor
manufacture placed a section of steel from each new delivery in a brine
(salt water) bath for some time, and if any rust developed they rejected the
whole delivery. Most steel is made with a certain proportion of scrap metal
much of which will be heavily corroded. It is the melting process that
allows this oxidised material to rise to the surface, being less dense than
good steel, and is poured off as slag. Poor quality steel rusts because it
wasn't heated to a high enough temperature for long enough to get rid of it
all, so the finished product contains pockets of oxidised material embedded
in the rolled strip long before it is even pressed into panels! This causes
corrosion to develop from within the steel no matter what paint and
protection is applied to its surface. This became a major problem in the UK
in the 70s and 80s as manufacturers tried to cut costs by buying cheaper
steel to offset massive wage rises. Eventually things got so bad they had
to revert to quality steel and were able to give 5-year or more
anti-perforation guarantees, which was a guarantee against corrosion
starting from inside the metal, not from the surface due to weather
conditions and salt on the roads.
PaulH.
----- Original Message -----
From: <BarrMark262@aol.com>
To: <mgs@Autox.Team.Net>
Sent: Thursday, November 11, 2004 4:11 PM
Subject: Water+steel=rust?
> We all know when moisture and steel mix, the result on our cars is rust.
>
> Question is, what causes this to happen?
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