In response to Rick Morris question about preservation of a piece of 18th
Century iron with a "polymeric rust converter", I recommend that you not
use it especially if surface detail is important.  This stuff is designed for
rusty spots on automobiles and will provide a relatively stable surface that
can be painted, if done correctly.  What it will not do is address the cause of
the corrosion.  If the iron in question has been in contact with soil or was
under water it probably is contaminated with chlorides which will cause it to
continue to corrode beneath whatever surface the product may give it.
There are methods of chloride removal and corrosion reduction that aren't
very costly for one relatively small piece ( not a cannon) that will truly
stabilize the piece.  There are also available formulae for creating
passivating conditions in solution so you can store your piece at greatly
reduced (non-measurable) corrosion rates until you are able conserve it
properly.
 
With more information, I could be more specific
 
Curt
 
Curtiss Peterson
THE RESCUE COMPANY
Box 88
Rescue, Virginia  23424
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