WINDHOVER is a dramatic stainless steel sculpture created by the late Lenton Parr, located on the eastern foreshore of Port Phillip Bay, in Sandringham, Melbourne.
Unveiled in December 2001, the sculpture's vertical lines and arcs are evocative of the yachts often seen sailing out on the bay.
However, two-and-a-half years of exposure to salt spray from the bay had taken its toll, turning the surface of the stainless steel a blotchy brown.
Called tea staining, it's caused by deposition of salt on the surface which is then trapped in the crevices of the brushed finish. Regular reactivation by rain has perpetuated a corrosion cycle leading to quite rapid and severe deterioration.
The problem was how to clean the sculpture. Conventional products containing hydrofluoric acid are too aggressive, risking damage or discolouration to the surface and creating an environmental and safety hazard when used in such a public place.
To avoid these problems, two products from Bio-Chem, represented by Revolution Advanced Metals & Materials , were chosen -- INOX-Clean and INOX-Protect.
INOX-Clean is based on a low concentration of phosphoric acid, and is safe to handle - skin contact does not cause the burning associated with hydrofluoric or nitric acid preparations. Brushed on and left to react for 3-4 hours, the brown tea-staining gradually disappeared. The residue was simply washed away with water.
Because it is also biodegradable (in accordance with current EU guidelines), run-off into the surrounding ground was not a concern. In some particularly bad sections a second application was necessary to completely remove all traces of the staining, but left a completely blemish-free surface.
One of the problems with washing stainless steel with water is the streaking caused by drying - this was very noticeable on the sculpture. However, an application of INOX-Protect solved this.
Simply sprayed on, wiped over, then polished with a dry cloth, all streaking vanished. The INOX-Protect (a water-based product, also biodegradable) left an invisible film that stopped further streaking and fingermarks.
Best of all, it brought up the lustre of the brushed finish, and left Windhover looking as good as the day it was made. Regular re-application should maintain the finish and help prevent tea staining in future.
With the increasing usage of stainless steel in public infrastructure on our coastal fringes, keeping it clean and looking good should no longer be a problem.