Heat coloring or lead dipping stainless steel
I have access to some stainless steel (or Chrome iron?) sheets which I want to use for roofing. I need to color them a dark color. The Chromate/ sulphuric acid process looks too hazardous. Does anyone have any experience of heating to change color or a way of hot dipping to coat with lead.John Sewell
Hi, John. I'd suggest trying to find out exactly what the metal is (because coloring processes react with the base metal and the same chemicals will give different color or no color to different metals), then consulting the Metal Finishing Guidebook, which has a chapter on Coloring of Metals.
As an aside, our society's paranoia over metal finishing chemicals has gone sublime as we see people now wanting to abandon simple proven aqueous processes in favor of dipping into molten lead -- a chronic cumulative poison and source of toxic red lead oxide -- not to mention the thermal and explosion hazards of molten metal. In other words, don't dip it in lead :-)
Ted Mooney, P.E. RET
Pine Beach, New Jersey
I am using a copper/silver anode charged with 24 volts at 10amp/20 volts. The anode is inside a stainless steel cylinder immersed in corrosive water, sodium hypochloride. I removed the cylinder from the water and as it dried appeared to give off a toxic gas, not visible, no smell, but causing severe irritation to the eyes. Exposure time about 15 minutes, however the irritation remained some 5-6 hours. The irritation caused extreme eye redness. An observer also experienced the same difficulties. No other leakages or mixture of any surrounding chemicals was detected.John Haeata
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