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lwinger
Joined: 21 Jun 2006
Posts: 229
Location: Tustin, CA
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 Posted: Tue Sep 26, 2006 7:20 am Post subject: Corrosion Protection Answers |
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In my quest for answers to the age-old question about internal corrosion protection, I contacted the folks at PTI (http://www.aircraftspruce.com/menus/cs/pti.html) for answers. As it turns out, my conversations ended with the President, Steven Andrews, actually coming by my office to pick up some scrap 6061-T6, a few actual rudder parts, and a Scotch-Brite pad (7447). After decades of serving the defense and commercial markets, PTI is waking up to the general aviation and homebuilt market. When I mentioned some of my questions (which some on this list seem to share), he was anxious to provide answers.
He took the parts and they applied their zinc chromate and non-zinc chromate primers to perform adhesion tests. These were parts which had normal marks that you get from working aluminum into compound shapes. Half of the parts were scuffed with Scotch-Brite and the rest were not. All parts were solvent cleaned with isopropyl alcohol (talk about inexpensive and easy).
The bottom line is that the tests showed high levels of adhesion, regardless of whether scuffing was done or not. I have pictures available on request. The use of a single, inexpensive solvent was partly in my response to questions about using Alumiprep 33 and Alodine. Their contention is that such time-intensive preparation is not required.
My final question to him was this: “Is adhesion all that matters?” I asked because I know many builders are using the NAPA Self-Etching Primer or similar products and claim that is adheres very well. Here is his response.
“Well, adhesion is not the only issue. Obviously though, the primer has to adhere to protect. I do not know who manufactures the product that NAPA sells so I do not know how it is formulated. If it is a generic zinc chromate primer (which I suspect it is) then there is no telling what the quality of the resin system is, how it will hold up to chemical exposure, changes in climate, exposure to humidity, high heat or extreme cold. Whether it has the flexibility to expand and contract with the metal given altitude changes and the other unique environmental challenges unique to aviation as compared to the automotive environment I cannot say. But I can say that our product is specifically formulated for aircraft -- actually military aircraft. It is made with the highest quality resins available and conforms to the strictest standards as set out in the Military Specification to which it is formulated. So once it adheres -- it will perform.”
My reason for contacting PTI was that I liked what I read on the Aircraft Spruce website about their products and client list. They make the landing gear coatings for all major airlines, and their products are used in the interior and cargo holds of the Space Shuttle Challenger. Their customers since 1947 have a lot higher standards to meet than the project I’m buiding in my garage.
If nothing else, they have saved me lots of time and money in what appears to be unnecessary prep for priming. From now on, I’m using isopropyl alcohol until the rag comes off clean, then I’m priming with an aviation-specific product. My purpose in sending this message is to pass along information in case anyone on the list has been wrestling with similar issues.
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_________________
Larry Winger
Tustin, CA
Plans building 601XL/650 with Corvair
Installing fuel system
www.mykitlog.com/lwinger |
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p.mulwitz(at)worldnet.att
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| Posted: Tue Sep 26, 2006 8:28 am Post subject: Corrosion Protection Answers |
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Hi Larry,
Thanks for the great information.
I wish to add one thought on the fancy priming
issue. You might want to use different
techniques for internal paint vs. external finish
paint. The simple approach is probably overkill
for internal use, but certainly good enough. For
the external finish, I would go the complete
route of alumiprep, alodine, primer, and top
coat. The difference is that the external finish
is subject to heavy sunlight exposure along with
nasty weather and related stuff.
Paul
XL fuselage
At 08:20 AM 9/26/2006, you wrote:
| Quote: |
In my quest for answers to the age-old question
about internal corrosion protection, I contacted
the folks at PTI
(http://www.aircraftspruce.com/menus/cs/pti.html)
for answers. As it turns out, my
conversations ended with the President, Steven
Andrews, actually coming by my office to pick up
some scrap 6061-T6, a few actual rudder parts,
and a Scotch-Brite pad (7447). After decades of
serving the defense and commercial markets, PTI
is waking up to the general aviation and
homebuilt market. When I mentioned some of my
questions (which some on this list seem to
share), he was anxious to provide answers.
He took the parts and they applied their zinc
chromate and non-zinc chromate primers to
perform adhesion tests. These were parts which
had normal marks that you get from working
aluminum into compound shapes. Half of the
parts were scuffed with Scotch-Brite and the
rest were not. All parts were solvent cleaned
with isopropyl alcohol (talk about inexpensive and easy).
The bottom line is that the tests showed high
levels of adhesion, regardless of whether
scuffing was done or not. I have pictures
available on request. The use of a single,
inexpensive solvent was partly in my response to
questions about using Alumiprep 33 and
Alodine. Their contention is that such
time-intensive preparation is not required.
My final question to him was this: “Is
adhesion all that matters?” I asked because I
know many builders are using the NAPA
Self-Etching Primer or similar products and
claim that is adheres very well. Here is his response.
“Well, adhesion is not the only
issue. Obviously though, the primer has to
adhere to protect. I do not know who
manufactures the product that NAPA sells so I do
not know how it is formulated. If it is a
generic zinc chromate primer (which I suspect it
is) then there is no telling what the quality of
the resin system is, how it will hold up to
chemical exposure, changes in climate, exposure
to humidity, high heat or extreme cold. Whether
it has the flexibility to expand and contract
with the metal given altitude changes and the
other unique environmental challenges unique to
aviation as compared to the automotive
environment I cannot say. But I can say that
our product is specifically formulated for
aircraft -- actually military aircraft. It is
made with the highest quality resins available
and conforms to the strictest standards as set
out in the Military Specification to which it is
formulated. So once it adheres -- it will perform.”
My reason for contacting PTI was that I liked
what I read on the Aircraft Spruce website about
their products and client list. They make the
landing gear coatings for all major airlines,
and their products are used in the interior and
cargo holds of the Space Shuttle
Challenger. Their customers since 1947 have a
lot higher standards to meet than the project I’m buiding in my garage.
If nothing else, they have saved me lots of time
and money in what appears to be unnecessary prep
for priming. From now on, I’m using isopropyl
alcohol until the rag comes off clean, then
I’m priming with an aviation-specific
product. My purpose in sending this message is
to pass along information in case anyone on the
list has been wrestling with similar issues.
--------
Larry Winger
Tustin, CA
601XL #6493 from scratch
Stabilizer skeleton ready to rivet
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lwinger
Joined: 21 Jun 2006
Posts: 229
Location: Tustin, CA
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| Posted: Tue Sep 26, 2006 9:07 am Post subject: Corrosion Protection Answers |
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My questions of PTI were about internal corrosion protection only. I know they have completely different answer when priming for external painting. Thanks for highlighting that difference.
On 9/26/06, Paul Mulwitz <p.mulwitz(at)worldnet.att.net (p.mulwitz(at)worldnet.att.net)> wrote: [quote]--> Zenith-List message posted by: Paul Mulwitz p.mulwitz(at)worldnet.att.net (p.mulwitz(at)worldnet.att.net)
You might want to use different
techniques for internal paint vs. external finish
paint. [b]
| | - The Matronics Zenith-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Zenith-List |
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_________________
Larry Winger
Tustin, CA
Plans building 601XL/650 with Corvair
Installing fuel system
www.mykitlog.com/lwinger |
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