Date: Tue, 22 Jul 2008 18:14:51 -0400
Reply-To: Mike <mbucchino@CHARTER.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Mike <mbucchino@CHARTER.NET>
Subject: Re: The DEEP, DARK secret of fiberglass exhaust wrap discovered
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Rust is a form of corrosion; corrosion is not neccessarily
related only to rust (breakdown of a ferrous metal due oxidation).
I've held FAA Airframe & Powerplant mech licenses for 27 years, so I do
have formal training and years of hands-on experience. Aviation mechanics
frequently replace stainless steel exhaust sytem components on aircraft due
to corrosion, not rust. The high temps and gas flow cause erosion of
materal, eventually thinning things enough to cause a hole to blow out
(usually on the bends where concentration is highest). This corrosion
process happens many years later than rusting would happen on a mild steel
system, so the benefits of using an all-stainless system is obvious.
My question is;
How long does the average expensive OEM Vanagon mild steel system last,
versus a very expensive aftermarket stainless Vanagon exhaust sytem, if all
factors are the same? The added cost of the stainless system must greatly
outweigh the shorter life of the stock system. How many stock set-ups would
you have to replace, to equal the cost of the more expensive one?
I'm not factoring in replacement labor here, just parts.
Mike B.
---- Original Message -----
From: "BenT Syncro" <syncro@GMAIL.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Tuesday, July 22, 2008 5:11 PM
Subject: Re: The DEEP, DARK secret of fiberglass exhaust wrap discovered
> 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
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