[SEL] Semi-OT: Engine valve alloys

[John Culp]

> Hi Richard,
>         If you think anything in that article has anything to do with 
> antique stationary engines please contact me off List--I have a bridge 
> for sale in which you may be interested!
>         Dave

Nevertheless it's interesting stuff. If the old engine builders had had 
modern valve metallurgy available to them, they'd've taken advantage of 
it.

That article's got a factual error about lead oxide corroding exhaust 
valves. It's the ethylene dibromide and dichloride scavenging compounds 
mixed in leaded gasoline to get the lead out of the engine. The 
halogens released when they burn form a low-melting-point mixture of 
lead salts instead of hard lead oxide, and that's what makes the 
familiar whitish tailpipe deposit in a clean-burning engine running on 
leaded gas. Some of those halogens will combine with the steel instead 
of the lead, though.

John Culp
Bristol, Tennessee, USA