Vapour phase corrosion inhibitors

[The following appeared on Museum-l and is reproduced here with the
permission of the authors]

My college George Bailey has the following points about the use of
VCI's. Kate is not I think talking primarily about archeological
materials. In Australasia our main concerns are modern materials and
technological items. I feel our approach may be a bit more scientific
than many when it comes to these items Anyway here is Georges comment.

    Hello Kate.

    Re: VPI's. I did some studies on VPI's at UCan in 1990. There are
    several things you need to consider when using VPI's, such as
    frequency of access to storage, air tightness of the storage system,
    organic materials and/or other metals in contact or proximity with
    the object, and of  course temperature and RH.  The studies that I
    did included mild steel, not iron, but I would expect that the
    behaviour of iron to VPI's would be pretty much the same. VPI's can
    be expensive & I wouldn't recommend them as the main means of
    protection in storage, but there are situations where the very
    nature of an object, makes the use of VPI's more attractive than
    other forms of storage. Metallic objects of intricate and complex
    construction, where the application of a protective coating is not
    feasible, are ideal candidates.  Note that VPI's need to be
    replenished or replaced after 2 years or less, depending on how air
    tight the storage system is. I suggest that you also look into
    dehumidified storage, as that may be a more efficient system for a
    large number of ferrous objects.

    At the Australian War Memorial we occasionally use VPI's for storage
    or display. We have found Cortec VCI-560 and Shell VPI 260 to be the
    best for ferrous objects, and Cortec VCI-307 the best for general
    protection of other metals. The Cortec products are fairly safe as
    far as toxicity goes, but I am not sure about Shell VPI 260, which
    is based on Dicyclohexylammonium nitrite (DICHAN). I would treat it
    as toxic. Also note that Shell VPI 260 will stain organic materials
    within its' atmosphere. Mary Gissing (Museum of Applied Arts &
    Science, Sydney) did some study on such effects, so I suggest you
    try to contact her. We have not, as yet, tested the Senson range of
    VPI's, but they look promising from their literature. Senson's Fax
    No. in Australia is +61 9 478 2076.

    Feel free to contact me if you need any more information. Nice to
    see you at the NZPCG/AICCM conference.

    Cheers,

    George Bailey.
    Conservator of Objects
    John Treloar Centre for Conservation Science
    Australian War Memorial
    +61 6 243 4534
    Fax: +61 6 241 7998

David Hallam
Senior Conservator of Objects
John Treloar Centre for Conservation Science
Australian War Memorial
+61 6 243 4534
Fax: +61 6 241 7998

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                  Conservation DistList Instance 8:31
                 Distributed: Monday, October 31, 1994
                        Message Id: cdl-8-31-005
                                  ***