Date:         Tue, 22 Jul 2008 14:11:32 -0700
Reply-To:     BenT Syncro <syncro@GMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         BenT Syncro <syncro@GMAIL.COM>
Subject:      Re: The DEEP, DARK secret of fiberglass exhaust wrap discovered
In-Reply-To:  <0b4201c8ec34$f66ad470$6401a8c0@PROSPERITY>
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On 7/22/08, Scott Daniel - Turbovans <scottdaniel@turbovans.com> wrote:


   stainless has a lot of properties that make it not as good as steel in
many applications.

I just want to interject something. Stainless steel is still steel. You must
mean mild or carbon steel.
As I understand it, stainless steel is nothing more than carbon steel with
some chromium added to
mix. As the chromium oxidizes, it forms a protective layer onto
the iron/steel in the alloy in a similar
way that zinc coated steel (galvanized) forms a protective layer over the
steel when the zinc turns
into zinc oxide. The difference, of course, is the chromium is 'throughout'
the material. It's in the
alloy.  My best non-metal comparison I can think of are countertops. In
Corian (and similar types) the
coloring is throughout the material vs. laminated tops such as Formica (and
similar types) which only
has coloring close to the surface. Corian would be similar in wear
characteristics as stainless steel.
Surface wears (chromium turns to chromium oxide) but it's still Corian
through and through. Formica
wears out (zinc in galvanized steel turns to zinc oxide) and eventually the
material of the countertop
is no longer protected. Same case with the metals. Stainless steel just
keeps going in going but not
forever. Eventually the material gets thin enough and as some have pointed
out - rusts through.

The amount of chromium content will determine at what rate the stainless
steel will deteriorate. Why not
dump more chromium in the mix? Well, chromium is not as strong as carbon in
steel. The more chromium,
the weaker the material. Like anything else, it's a balancing act of
anti-corrosive properties vs. strength.
Which brings me to the Vanagon application. Vendors offer not just different
alloys of stainless steel but
different gauge as well. Since there is no independent testing of the
durability of these products, it would
be good for someone to start tracking how well these commercially available
systems are holding out. You
know... more chromium wears longer from a corrosion point of view. But they
wear faster as in from cracks
due to metal fatigue, etc.

Aw, what do I know. I'm no metallurgist. English isn't even my first
language. Steel, steal, sounds the same
to me.



BenT  P. Ipez