Martin:
Who is the person and what are they doing?  Can you summarize?

Suzanne
----- Original Message -----
From: "Martin Read" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, January 07, 2003 11:22 AM
Subject: Rates of Encrustation of Submerged Artifacts


> This came up in the SUB_ARCH discussion group and thought some of you
might be interested or have something to add. Let me know and I'll post it
back to them.
>
> Date:    Mon, 30 Dec 2002 13:58:00 -0700
> From:    "Keith V. Littleton" <[log in to unmask]>
> Subject: Question About Rates of Encrustation of Submerged Artifacts
>
> Dear Fellow List Members;
>
> Does anyone know where I can find in the published
> literature, the results of research about how fast
> organisms encrust submerged artifacts or wreckage
> lying exposed on the bottom?  I am interested in
> how the rates of encrustation vary with depth and
> between fresh and salt water.
>
> Yours,
>
> Keith
> New Orleans, LA
>
> ------------------------------
>
> Date:    Sat, 4 Jan 2003 09:31:53 -0500
> From:    [log in to unmask]
> Subject: Re: Question About Rates of Encrustation of Submerged Artifacts
>
> In a message dated 1/3/2003 1:39:34 PM Eastern Standard Time,
[log in to unmask]
> writes:
>
> > No reply yet to your inquiry from anyone with a knowledge of the
> > archaeological literature.
> >
> > You may find something of use to you in the marine-biological sections
> > of the library. There is an extensive literature on marine fouling (tied
> > in to research on antifouling paints, schedules for cleaning the legs of
> > oil rigs and so forth). That is likely to focus on the first weeks and
> > months of immersion, rather than the following decades and centuries,
> > but it might be of some use to you. I regret that it is not my field and
..
> >
>
> I agree with Trevor that there are no book sources that I know of
detailing
> what you are looking for. I would like to add that any rates would have to
be
> specific for each material. From my wreck diving along the Northeast US &
> Canadian coast and in the Great Lakes I have seen steel develop over 1/2
inch
> of encrustation in 40 years or less (Rhode Island Coast) or only have
surface
> rusting after 100 years (Lake Erie).
>
> I would also say that the rate of crust growth will be very quick for the
> first few years and then drop off to almost zero after the object is fully
> encapsulated.
>
> As I know steel and iron the best, here are some observations.
>
> One of the biggest problem with modern steels are tramp metals if it was
made
> from scrap - almost 100% of all steel since W.W.II will have some scrap.
The
> exception is for aerospace steels that have to be from virgin melts by
> specification just because of the scrap contamination problems. These
tramp
> metals will really speed up the corrosion process. Next, the hardness of a
> steel will directly effect the corrosion rates. Harden steel has an
internal
> stress that promotes corrosion and some of these steels are classified as
> "Active steels" just because of this want to corrode.
>
> Getting away from steel, materials like iron develop corrosion products
much
> slower then steels. Perhaps John Broadwater can give you some thickness
from
> the USS Monitor on wrought and cast iron and perhaps some steel.
>
> Finally, in salt water if the wreck is in an area where corals can grow
> quickly they will survive much longer then other areas. Think about the
> Titanic and her corrosion rates vs. some of the W.W.I wrecks in Guam and
the
> Med that are covered by organic growth. This growth encapsulates the
metals
> locking out the salts and oxygen. You still have galvanic effects but they
> are much less then ordinary salt water corrosion.
>
> So I would think that any definitive study would be almost impossible due
to
> variables such as alloy, organic growth, galvanic effects, salinity, water
> temp,.....
>
> Good luck with you research and let me know if I can help in any way.
>
> Pete Johnson
>
>