Metal spraying

From New Scientist, 24 January 1998

    A brilliant way to protect outdoor art

    Metal sculptures that have lost their lustre after years in the
    open air can now be given a bright new sheen, thanks to a
    technique for spraying metals developed by weapons researchers
    in New Mexico. The process was originally designed to prevent
    corrosion in the containers that store nuclear weapons. Ideally,
    for a surface that is shiny and resists corrosion, says Kendall
    Hollis, a metallurgist who works at the Los Alamos National
    Laboratory, "you want something that is pore and defect-free".
    However, corrosion-resistant metals, such as stainless steel,
    are hard for sculptors to cast or machine, and techniques such
    as electroplating lay down a coating that is too thin for much
    mechanical polishing or shaping. The Los Alamos technique sprays
    the sculpture's surface with tiny droplets of molten metal. The
    metal is melted by an electric arc and then blown at the object
    with high-pressure gas. "It's analogous to paint spraying," says
    Rich Castro, who helped develop the process at Los Alamos.
    "Individual molten particles hit a surface, splat, and
    solidify." Because the droplets are so tiny, they carry little
    heat, and cool quickly. Castro says: "You can pretty much coat
    any surface," including wood, rock and cement. And with metals
    that have a low melting point you can even coat fabric or paper.
    The process works for any conductive metal, and can deposit
    layers ranging from just 1 millimetre thick to a couple of
    centimetres. One of the advantages is that artists can shape
    their sculptures in familiar metals such as aluminium or bronze,
    then coat them with a corrosion-resistant finish, such as
    nickel. The nickel coating can be thick enough to cover welding
    joints and withstand final polishing by the artist, while
    recoating covers surface damage.

Ton Cremers

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                  Conservation DistList Instance 11:67
                 Distributed: Friday, February 6, 1998
                       Message Id: cdl-11-67-004
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