Coolant Leakage Solved- BUT now BOOST

[Phil Rose]

At 4:51 PM -0700 8/4/05, Bernie Benz wrote:
>  > From: Phil and Judy Rose <pjrose at frontiernet.net>
>>
>>  At 9:02 AM -0700 8/4/05, Bernie Benz wrote:
>>>>  From: Taka Mizutani <t44tqtro at gmail.com>
>>>>
>>>>  Bernie-
>>>>  Isn't the stock system stainless? I never checked to see if it was
>>>>  magnetic or not, but the piping definitely looked like stainless.
>>>  I don't believe so, just well protected mild steel.  They do rust out, I'm
>>>  on #2.
>>>>
>>  Bernie,
>>  Taka is correct, as certainly the stock Audi exhaust pipes are
>>  stainless and it's  widely accepted as fact (except possibly by you)
>>  that the exhaust system is predominately made of stainless steel
>>  components. I'm surprised that you think that "well protected mild
>>  steel" could survive 15 rust-belt winters (both my '91 200q cars
>>  still have their original exhaust systems, although some muffler
>>  perforation has occurred). Even stainless steel cannot avoid eventual
>  > corrosion by calcium chloride.



>Painless Stainless comes in all degrees of corrosion resistance under high
>temp exhaust conditions.  Only the austenitic (high chrom/nickel) alloys are
>non or only slightly magnetic.

Yeh, but so what? Anyway that should be "austentitic".

>Using the magnetic test,
>the down and back pipes are nonmagnetic.
>The cat's outer skin is magnetic, as is that of both mufflers.
>The intermediate and rear piping are also magnetic.

Magnetic or not...stainless steel nevertheless

>CaCO4?

No, calcium chloride is CaCl2.  It's used, along with ordinary sodium 
chloride, to salt the roadways here in the east.

>  I've not seen an exhaust system deteriate, loose its functional
>effectiveness, from outside contaminates, always corrosion from the inside
>out.

Once again, so what? Your previous post implied that you didn't 
believe the Audi exhaust to be stainless because they did not last 
forever (or no more than 10 or 12 years?). So my comment (about 
"eventual corrosion" of stainless steel) was merely to emphasize that 
use of stainless steel is no guarantee that corrosion will not occur 
and also that salt will accelerate that process.  My specific mention 
of calcium chloride (a component of road salt) was largely motivated 
by recalling the years when I ran a laboratory that was equipped 
stainless-steel countertops and sinks and in which we routinely 
prepared large volumes of a calcium chloride solution.  If stray 
droplets of the salt solution (or the solid salt particles) were not 
carefully cleaned up, it required only a matter of hours (overnight) 
until you could see dark rust stains, and-- after additional time 
--there would be severe pitting in the stainless steel surfaces. We 
could not use stainless steel tubing or fittings to transport those 
salt solutions--only plastic.

As to internal corrosion being the main source of exhaust system 
perforation--yes, perhaps that's true as I've heard that claim often 
enough. What I do know is that ordinary (non-stainless) exhaust 
systems here in the heavily salted northeast frequently (usually?) 
rust away within a few years; whereas the Audi systems last at least 
10-12 years.  Where I grew up (Arizona) an *ordinary* steel exhaust 
generally lasted the life of the car. Perhaps we got very little 
"internal" corrosion driving around Tucson, I don't know; but I sure 
as heck _do_ know that our cars never saw any exposure to road salt.

Phil
-- 

Phil Rose
Rochester, NY
mailto:pjrose at frontiernet.net