question about ceramic coatings

[nluker]

Kurek, Larry wrote:
> 

> 
> Yes, it is a good idea to coat the inside of the pipes...probably more
> so than the outside. Reason being, the heat contained in the exhaust
> goes as far as the coating, and is then retained. If you only coat the
> outside...it will look pretty, and reduce your underhood temps, but the
> pipe will burn out quickly.

I know this thread is a bit old but one of my mates is a head mech at a
repair shop and we were talking about the thermal insulating tape you 
can wrap around your exhaust sytem.He first saw it on customer cars
about 2 years ago and was very impressed about how cool it made the
engine bay and how much easier it was to work on the cars; until he
slipped with a screw driver hit the exhaust manifold with the tip of his
screw driver and went straight thru !
Luckily he had a spare manifold in stock. When he took the old one off
he found that the manifold (which was cast) was not rotted but had gone
brittle and that he could punch holes in it quite easily with his screw
driver. A while later another mechanic at his work did the same thing on
another car that had thermal insulating tape on it. There thoughts were
that the extra high temp that the manifold was know sitting at for
prolonged periods of time had crystalised the metal and had turned it
brittle and weak.
was now subject to