Here's the scoop on the black coating on my valves...
It's a PVD (Physical Vapor
Deposition) black nitrate containing trace elements of chromium & titanium
in an inert ceramic plasma. It's designed to prevent
wear, decrease friction and rapidly dissipate heat thru migration out of the
treated part. It's the latest high-tech thing in valve coatings and supposedly
outlives the valve... even the exhaust valves. Additionally it prevents carbon
build-up from forming on it's surfaces by some
high-temp (3,000+F) Teflon/Silverstone-like qualities within the inert ceramic
plasma that repel combustion by-products giving them nothing to adhere/cling
to. Apparently the stainless steel valve inside would melt before the coating
could fail.
I was told this originally when I dropped the valves off but couldn't remember
but a few snippets of it. Someone asked the other day and curiosity got the
best of me so I called the plating/coating company I used and thats what they told me.