[TheForge] buried metal artifacts

[Andrew Vida]

On 6/29/2012 3:01 PM, terry l. ridder wrote:
> hello;
>
> while reading the bbc news i came across an article about a hoard of
> roman and celtic coins found buried in the clay ground of the channel
> island of jersey.
>
> Jersey pair find Celtic and Roman coins worth up to £10m
> http://www.bbc.co.uk/news/world-europe-jersey-18599281
>
> i realize that part of the answer is the very nature of the soil that
> the items are buried in. also the geography of the location. is it
> damp? is it wet? is it well drained? is the soil acidic or caustic? how
> deep were the items buried? what were the layers of soil covering the
> items?
>
> just how does metal last, buried for all those centuries without corrosion?
> just how does metal last, buried for all those centuries without undergoing
> the chemcial changes to either oxidize the metal, combine to make
> nitrates, nitrites, sulfates, sulfites, etc.

Gold will last indefinitely as it is almost perfectly inert.  Silver 
will degrade, but that can take a long-ish time.  Iron would have been 
wrought so the silicate layers protect it for a long time even in 
moderately hostile environments.  I've fished wrought out of the waters 
of NJ, some of which is almost certainly 200+ years old, much of it 
having come out of a very old ship's graveyard in Perth Amboy.  The iron 
in Carteret from the old US Metals site and others might be a century or 
more old in some cases.  Plenty of etching, but plenty of iron remains.