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"Finishing a Stainless Steel Tree"
February 5, 2010
I belong to a Blacksmithing group which is well on the way to forging a life size Stainless Steel eucalyptus Tree as a memorial to bushfire victims et al affected by last years devastating bushfires across Victoria, Australia. It's called "The Tree Project". All components of the tree i.e., trunk, branches, twigs and approximately
3000 gumleaves have, or will be, forged from solid 304 or 316 SS stock. It is hoped the finished article will be "shiny" and remain so in its final location out of doors.
Obviously the forging process results in an oxidized surface which must be removed. At present we are finishing leaves which have been sponsored by supporters of the project by first wire brushing with an SS wheel, pickling with a pickle paste and polishing with a rag wheel. In their shiny state these leaves are photographed and a photo sent to the sponsor. Thereafter we have just let them be. Some have oxidised slightly while some remain shiny. There are, however some 2000 leaves which will go straight from the forge to a branch without finishing. Our thinking is that managable branches of leaves and twigs can be finished as a whole and attached to the tree when polished and passivated, leaving only small areas of weld to clean up. These branches will consist of previously polished leaves and untreated leaves at a ratio of about 1 to 2.
How then would be the best way to achieve a permanently shiny surface on a branch of twigs, leaves and gumnuts which is 400 to 500mm in diameter? We have considered chemical polishing or sandblasting which leaves the passivation process but there may be other ways we are unaware of. Having made various enquiries we have various answers to our problems and invite your readers thoughts as well. It's all grist to the mill.
There is one final consideration. There are approximately 500 sponsored copper leaves as well. These are just pickled, polished and photographed and will be left to attain a leafy green patina. Since they form an integral part of the fabricated branches they will be affected by any treatment we apply to the stainless steel. For example a polishing chemical that will shine up the stainless leaves but at the same time eat away the copper leaves is probably not going to serve our purposes well!
I hope readers can shine some light on our dilemma. For more information on the Tree visit http://www.treeproject.abavic.org.au/index.html
Hobbyist Blacksmith - Melbourne, Victoria, Australia
February 9, 2010
This is a typical application for electropolishing.
The combination of copper and stainless steel is no problem.
The copper will come out of the baths with a cleaned red surface and will get its green patina in a short time.
The stainless steel will keep its luster and shine forever with an electropolished endfinish.
- Diksmuide, Belgium, Europe.