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Letter 42020 Black oxide and skin burns [Michigan]August 25, 2006 I have a customer who is reporting burns and skin irritation from
parts that have been black oxide finished. There is a white soda type
material that is leeching from weld gaps and cracks. Is this normal?
Is there something that can be appied to the metal to neutralize the
white soda material, remove it or render is harmless to the
skin?
Daniel Richards
August 25, 2006 The plating shop, whether it be in-house or a subcontractor, must fix this problem, Daniel. Black oxiding is done in a solution that is extremely high in caustic content and must be thoroughly rinsed! This is a matter of bad execution, not bad selection of finish. It is very common that a useful process requires noxious chemicals to accomplish; for example, food processing equipment is electropolished in very highly concentrated acids, which obviously must be thoroughly rinsed, just as your parts must be.
September 1, 2006 I would also address this problem with the welding contractor, have hime make sure his welds are free of voids, which will entrap the solution. Its very nice when both a manufacturer, and coater of a part work together to solve a problem. I couldnt tell from the picture, but if that part is hollow, it would be unreasonable to expect the plating contractor to thoroughly rinse out any processing fluids that have become entrapped in a hollow part that has been sealed by poor welds.
September 7, 2006 You're certainly correct, Marc, and I completely missed the fact that that tube is probably hollow! Better wake up the engineer, too. There probably could and should be large holes somewhere.
Dear Reader: please choose what you want to do--
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