Electropolishing stainless steel sculptures. (Installations).
Peter Crownshaw's tree was commissioned by the village of St Michael's near Tenbury Wells to celebrate the millennium and stands on the main road into the village. Made from 316 grade stainless steel, the tree has a three metre trunk and the branches are adorned with 360 plasma cut leaves stamped with the villagers' names. The forged components were first pickled by Anopol to clean them and then electropolished -- to enhance corrosion resistance and the appearance of the tree.
Paul Amey's first sculptures in stainless steel were silvery 'cods' commissioned by Waveney District Council for a historic site in Lowestoft. "I mistakenly used 304 grade stainless. The parts were welded together and then shot blasted to clean the welds and give a uniform 'silk' finish," he says. "What I didn't know was that welding and shot blasting seriously reduced the ability of the surface to resist corrosion. We had to demount the sculptures from the wall an d take them in pieces to Anopol's plant in Birmingham for electropolishing."
Anopol was able to increase the corrosion resistance very considerably. Resistance to rust was particularly important as the sculptures are located downwind from an industrial estate and a mile from the sea. "My choice of stainless as a material has largely been driven by the requirement for public art to be long lasting," Paul Amey explains. "This was a major problem with the initial cod sculptures but electropolishing seems to have saved the day."
Amey's latest work uses stainless steel for the wings of damselflies. A 'flight' of 40 or so damselflies is now located in a woodland setting to create a blue and silver 'river' through the forest. The damselflies are also sold through galleries and sculpture gardens in England and Holland.
The corrosion resistance of stainless steel comes from a thin passive oxide film on the surface which is easily damaged during fabrication by handling, welding, pressing or rolling -- all of which can be involved in the fabrication of a sculpture. Electropolishing removes surface impurities and restores the vital passive film. A highly skilled technique, it uses direct current and chemicals to remove a fine surface layer -- typically 20-40 micro-metres. The result is a smooth, shining finish much less vulnerable to corrosion and with the aesthetic appearance sculptors are seeking.
Apart from works of art, the technique is used for more prosaic construction items such as balustrading or exterior fasteners in seaside or polluted industrial environments as well as other applications where a totally clean, uncontaminated surface is imperative. Surgical implants and instruments, pharmaceutical and hospital equipment, food and drink processing are obvious examples. But the automotive, domestic appliance, printing and fabric making industries also specify electropolishing for both engineering and aesthetic reasons. The use of electropolishing in the UK, however, lags behind continental Europe where it is widely specified for virtually all stain less steel items.
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