How can I plate stainless steel to give it an antique black finish? One of my customers is asking for this process! S.C.
Stainless steel is blackened using a molten sodium/potassium dichromate bath. While the process sounds nasty, it is fairly widely used. The bath consists of 1 lb each of sodium and potassium dichromate. The bath is operated in the 750-800F range. All the usual precautions must be followed when dealing with concentrated, hot oxidizing materials. In addition you must deal with the environmental issues that go with hexavalent chromium.
I think your best bet is to contact some of the vendors listed in the “Suppliers” section of pfonline by clicking on Plating and Anodizing Processes, then Blackening Processes, Solutions or in the Products Finishing Directory and Technology Guide under Blackening Processes, Solutions. If you only have one customer who needs this finish you might consider out-sourcing the work. The American Electroplaters & Surface Finishers Society, 407-281-6441, publishes a Shop Directory each year that lists many finishing shops. One of the categories is black oxide finishes.