RE: [DML] Custom Made Gas-Flap door

["PJ Grady" <rob@xxxxxxxxxxx>]

After my post on stainless exhaust studs Martin G. sent me an e-mail
explaining his negative view on combining stainless and aluminum. He
suggested a test which involved soaking a head with our s/s stud installed
for a week in a salt water bath for a week to see if any galvanic action
occurred. I did this test for two weeks in heavily salted water and then
removed the head to dry. There was no trace of rust or galvanic action on
the stud and I unthreaded it by hand after the initial turn to loosen it.
The head however showed a heavy salt buildup suggesting a salinity level
approaching the Great Salt Lake! I did put a dab of high temp Anti-seize on
the installed thread, as we've been doing for twenty odd years on the
original studs when replacing them, and am very confident that this reduces
the chance of galvanic action to a minimum. After about 250 exhaust manifold
jobs I'm looking forward to NOT having to replace the studs every time an
exhaust gasket wears out. BTW we've been changing air cleaner mounting bolts
to stainless for over twenty years and have never had one seize (WITHOUT
using Anti-seize}. This is what led me to believe that, in the real world,
stainless studs (hardened of course) are the way to go in solving the rusted
stud syndrome. I firmly believe that mild steel has a much higher degree of
galvanic action than stainless. Our exhaust kits now feature stainless studs
for those of you interested. I have a number of new products that haven't
made it onto our website yet such as these studs. Unfortunately I'm better
at envisioning and making new products than marketing them. Now....let the
nay Sayers begin!

Robert Grady  

-----Original Message-----
From: tobyp@xxxxxxxxxxxx [mailto:tobyp@xxxxxxxxxxxx] 
Sent: Thursday, March 25, 2004 5:29 PM
To: dmcnews@xxxxxxxxxxxxxxx
Subject: Re: [DML] Custom Made Gas-Flap door

Ed - When you put aluminum and stainless steel (or mild steel for 
that matter) together in close proximity, and add moisture, you get a 
wonderful battery.  The aluminum starts to dissipate, leaving a white 
powdery corrosion product called aluminum oxide.  All European cars 
with aluminum skins attached to steel frames require a isolator ply 
between the two materials to prevent the body skins from 
disappearing.  In the aerospace industry, when we put aluminum and 
stainless steel together (which happens a lot) we apply two coats of 
a chromium-rich epoxy primer to each material, so we have four coats 
of paint for protection.  We also fay seal the pieces together with a 
high-performance sealant so that no moisture can get between the 
layers of dissimilar materials, and install all fasteners with 
sealant as well.  In short, without extensive protection, putting 
them together is a bad idea.


Toby Peterson  VIN 2248 "Winged1"
DeLorean Parts Northwest, LLC
www.delorean-parts.com 


--- In dmcnews@xxxxxxxxxxxxxxx, "Ed Garbade" <edgarbade@xxxx> wrote:

> Can anyone give me a definitive answer with respect to dissimilar 
metal galvanic corrosion between stainless and aluminum?
> 
> Is it a problem or not?





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