Mac, You can do black oxide coatings on stainless steel. You can also use a PVD (Plasma Vapor Deposition) coating of AlTiN (Aluminum Titanium Nitride - also called TiAlN) - which makes a very nice black shade on steel/stainless steel with fine detail - added benefit is really good abrasion resistance.
Just Google for "PVD" "Black Oxide" "Stainless Steel" and "Black PVD", etc. Most major metropolitan areas have at least one plasma coater. The PVD will tend to be expensive - but not too bad if its a high end custom dial. The bigger problem may be a size limitation - most PVD coaters do smaller parts, like cutting tools. However - they are accustomed to doing a wide variety of special and unique parts / medical parts / etc- so don't be afraid to ask. Black oxide is just not as durable - but probably perfectly adequate - size should not be a limitation. We use it for color only. A third choice is nitriding - We use one called QPQ which means Quench Polish Quench - it may work on Stainless. Its looks about the same as Black Oxide (nicer actually), and costs about the same (perhaps slightly more), and size is not an issue - but it offers a lot more corrosion protection than black oxide. You might want to ask about corrosion, usually these coating have no effect or a positive effect - but just because you have stainless as the base doesn't mean its a given - you might get a counter intuitive result. It may also depend on the exact alloy of Stainless you're using. The stainless might need to be passivated first. Talk to the coater. - Ben Hoffmann Mac Oglesby wrote: > Hello friends, > > Does anyone know a simple, safe, and inexpensive method to > permanently darken stainless steel? > > I'm involved in a project to create a vertical decliner (48 inches > wide by 30 inches high by 1 inch thick cast concrete) sundial for our > town's Municipal Center showing hours until sunset. For the hour > lines we intend to use 1/4 inch square stainless steel bars imbedded > into the concrete. > > Test castings show that, when sunlit, the imbedded bars appear dark > from most viewing angles, but that from some angles reflect light so > as to almost disappear. Although the changing appearance of the hour > lines might be considered a positive feature, I'd rather the hour > lines always looked dark. > > Thanks for any suggestions. > > Mac Oglesby > > --------------------------------------------------- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial
