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, 鈥測ou
want something that is pore and defect-free鈥�.
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.
Advertisement
The Los Alamos technique sprays the sculpture鈥檚 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. 鈥淚t鈥檚 analogous to paint spraying,鈥� says Rich
Castro, who helped develop the process at Los Alamos. 鈥淚ndividual molten
particles hit a surface, splat, and solidify.鈥�
Because the droplets are so tiny, they carry little heat, and cool quickly.
Castro says: 鈥淵ou can pretty much coat any surface,鈥� 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.