Hello Dave,

Thank you for your informative posting.  There is a conflicting information
out there, and I am one of those people in the field charged with caring
for iron objects (kitchenware, militaria).  Can you give an example of
non-ionic as opposed to an organic oil? For example, I have a few iron
kettles that got rusty in the bottom (inside).  Should these just be
brushed out, or treated with oil?

Thanks

Chris Robinson





                      David Harvey
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                      Sent by: Museum            Subject:  Re: rusty tools
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                      01/08/2004 12:47 AM
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As an objects conservator who spent many years devoted to metals
conservation let me correct a few assumptions here. One must be able to
distinguish between a stable oxidized patina and active corrosion. The term
"rust" can mean both! If one leaves active or potenitally active corrosion
on a ferrous object it will continue to corrode. Ferrous corrosion erodes
under the surface of the object or artifact in the form of pits and it also
can leach ferrous ions outward forming a corrosion crust. Corrosion is an
electochemical phenomenon and is driven by moisture, the presence of acids
and salts and pollutants, and oxygen. Also contact with dissimilar metals
such as brass will cause galvanic corrosion. So if you wanted to preseve an
artifact by leaving the rust in situ then keep it really, really dry and in
an anoxic environment. To simply wax over a rusted or dirty surafce will
certainly do more harm than good. So some sort of cleaning might be in
order. if an oil is used then it should be a non-ionic oil (never orgainc)
and should be formulated to lossen and stabilize corrosion products. That
being said the current standard in terms of historic tool conservation is
to carefully remove dirt and active corrosion but to leave a stable patina
alone - so folks, put away your wire brushes and naval jelly. You also need
to take care to protect any wooden components from and cleaning products
used on the ferrous part of the tool.

That is about as specific as I can get without actually seeing the object.
By the way, make sure you examine iron objects under very strong direct
light - there may be more extensive corrosion than you thin if you are just
seeing it under ambient room lights.

Cheers!
Dave

David Harvey
Artifacts
Denver, Colorado

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