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jeff(at)westcottpress.com
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 Posted: Tue Mar 11, 2008 4:04 pm Post subject: Fuel Tank Corrosion, with visual aid |
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I asked this question over 24 hours ago and so far there have been no
responses. With all that's going on with the list right now I'm
going to repost the question, with the attached picture in the hopes
I might get some feedback. Where's John Cox when you need him?
When I made my tanks... last May and June... I taped off the areas of
the skin that would be mated to the stiffeners and ribs with blue
painters tape. I roughened up the surface with scotch brite, cleaned
with aluma-prep and assembled with pro-seal. I left the baffle off
of the tanks as I was debating the installation of capacitance
senders instead of the floats. Over time (can't quite say how much)
I pulled up the painters tape.
So, I'm now ready to close up the tanks (with the floats) and find
that the right tank has a light corrosion in it... primarily under
the areas and at the edges of where the tape had been. I believe
this is both from the adhesive on the tape as well as my failure to
completely rinse the aluma-prep off in some areas. I can remove this
with a whole lot of elbow grease and a scotch brite pad. It comes up
a bit easier with aluma-prep and a scotch brite pad, but will then
run in to the nooks and crannies of the tank and create a new problem
somewhere else if I don't rinse quickly enough.
Will the presence of fuel in the tank act as corrosion protection and
keep this from progressing? Is this process something that stops
when the corrosive agent (the aluma prep, or the tape) is removed or
"used up," or is this a ball that once rolling won't stop?
Jeff Carpenter
40304
Scoth brite Hell
Awaiting your reply
IMG_0257.JPG
<pre><b><font size color="#000000" face="courier new,courier">
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indigoonlatigo(at)msn.com
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| Posted: Tue Mar 11, 2008 4:35 pm Post subject: Fuel Tank Corrosion, with visual aid |
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I looked at your post yesterday and really thought about it. First, I am not sure why this happened, chemically. I realize that Alodine not rinsed can cause corrosion, but I thought that acid removed corrosion. Are you sure the acid didn't do something to the painters tape, which then made it chemically bind to the aluminum or alter the aluminum?
When aluminum corrodes, does it not make aluminum oxide which is a white powder which easily comes off. Certainly re application of alumi prep should remove it. As long as you rinse the alumprep and don't let it dry, why would there be any problems. They put this stuff on the outside of a planes, nooks and crannies and all before painting.
My question, are you certain this is corrosion????
John G. (not a metalergist)
| Quote: | To: rv10-list(at)matronics.com
From: jeff(at)westcottpress.com
Subject: Fuel Tank Corrosion, with visual aid
Date: Tue, 11 Mar 2008 17:01:05 -0700
I asked this question over 24 hours ago and so far there have been no
responses. With all that's going on with the list right now I'm
going to repost the question, with the attached picture in the hopes
I might get some feedback. Where's John Cox when you need him?
When I made my tanks... last May and June... I taped off the areas of
the skin that would be mated to the stiffeners and ribs with blue
painters tape. I roughened up the surface with scotch brite, cleaned
with aluma-prep and assembled with pro-seal. I left the baffle off
of the tanks as I was debating the installation of capacitance
senders instead of the floats. Over time (can't quite say how much)
I pulled up the painters tape.
So, I'm now ready to close up the tanks (with the floats) and find
that the right tank has a light corrosion in it... primarily under
the areas and at the edges of where the tape had been. I believe
this is both from the adhesive on the tape as well as my failure to
completely rinse the aluma-prep off in some areas. I can remove this
with a whole lot of elbow grease and a scotch brite pad. It comes up
a bit easier with aluma-prep and a scotch brite pad, but will then
run in to the nooks and crannies of the tank and create a new problem
somewhere else if I don't rinse quickly enough.
Will the presence of fuel in the tank act as corrosion protection and
keep this from progressing? Is this process something that stops
when the corrosive agent (the aluma prep, or the tape) is removed or
"used up," or is this a ball that once rolling won't stop?
Jeff Carpenter
40304
Scoth brite Hell
Awaiting your reply
|
[quote][b]
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rnewman(at)tcwtech.com
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| Posted: Tue Mar 11, 2008 5:13 pm Post subject: Fuel Tank Corrosion, with visual aid |
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rnewman(at)tcwtech.com
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| Posted: Tue Mar 11, 2008 5:17 pm Post subject: Fuel Tank Corrosion, with visual aid |
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Jeff, I've had my wings in storage in my unheated hangar for a year now
with some blue painters tape holding some of the blue protective film back
in place. I'll try to get out to the hangar tomorrow and peel some tape
back and report on any corrision due to blue tape alone. The outer skins
were not treated with any chemicals (knowingly)
Bob Newman
TCW Technologies
www.tcwtech.com
---
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AV8ORJWC
Joined: 13 Jul 2006
Posts: 1149
Location: Aurora, Oregon "Home of VANS"
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| Posted: Tue Mar 11, 2008 5:46 pm Post subject: Fuel Tank Corrosion, with visual aid |
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I'm undergoing knee surgery tomorrow and still a bit heavy hearted over
the loss of a fellow member and what I ranked as one of the five
prettiest RV-10s ever completed. Damn it!
Aluma-prep uses acid to etch and make porous the Alclad finish. (and did
you know there is a top side and bottom side finish with visible grain
direction.) It is important in pursuit of a quality finish job that the
substrate be clean before application of aluma-prep. It is important to
neutralize the acid with de-ionized or distilled water. Think of the
acid as only a catalyst. Once the reaction begins, you need to
remediate and finish the process. The Alodine treatment is chromic acid
which hardens the porous finish. The final step is to wash again with
Non mineralized water. Often, builders use tap water and introduce
contaminants into the chemistry. (Anyone watching all the
pharmaceuticals being found in common tap water?) The porous
characteristic aides in later primer or sealer application with long
term adhesion. Remember that each side of the Alclad only has 5% pure
aluminum to turn whitish with oxidation. (You do the math on 0.016 or
0.032 sheet stock). To sand, scotchbrite or acid etch it too much is to
go right through to the copper hybrid under the pure aluminum. (It
alodines differently). Most Structural Repair Manuals spell out
replacement of base material when corrosion reaches 10% of original
thickness. That is why as the builder, we need to create our own SRM and
know the thickness of all materials we chose to use in assemblage. Just
because it came from VANS does not justify guessing later. When
corrosion is found, it must be 100% removed or just like a cavity, it
just keeps feeding itself. If we have to remediate beyond 10%, its off
for a new part(at the airlines). I don't think that is what you want to
hear. We often use MEK with proper skin protection to remove
contaminates and organics before re-alodining aluminum. Yes we do,
re-alodine. Every exposed piece gets the treatment.
One of the premises yet to be answered is how does "my beloved proseal"
hold up to adulterated corn squeezing inside the fuel tank. I would
love for the discussion to get elevated as to which components need to
be replaced to embrace subsidizing American Farmers instead of
importation of $110+ per barrel crude and amplify our balance of trade
deficit to Third World Tycoons. How about our President opening the US
strategic oil reserves to wipe out all of the US hedge fund investors
who are making this situation worse by pumping up artificial demand.
Fuel in the tank acts to reduce airborne oxidants but does not eliminate
them. That is the old wives tale of keep tanks topped off. The ball
will stop rolling when it is removed from the playing field. It doesn't
stop on its own. Sorry.
Study Intergranular and Exfoliation Corrosion.
"http://aluminium.matter.org.uk/content/html/eng/default.asp?catid=180&p
ageid 144416690" Use at least a 5X loop or 10X loop to view the degree
of corrosion remaining.
John Cox
40600
Pegleg Hell in Portland
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Tim Olson
Joined: 25 Jan 2007
Posts: 2872
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| Posted: Tue Mar 11, 2008 5:46 pm Post subject: Fuel Tank Corrosion, with visual aid |
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Jeff,
I am betting that the reason you don't get lots of replies is
that people are uncertain of their answer because they can't see
the thing for themselves very well. My thought is that the
corrosion was because of moisture under the tape. That tape
is porous....people should not use tape on aluminum for long
periods of time for that very reason. It's also why people
go with sealing primers if they're going to do primers, and
so on.
If it's not a structural issue at all, then I'd think you would
do OK to go either way...scotchbrite alone or with aluma-prep,
but you'll want to do some super rinsing after you're done, and
personally, I'd then treat it with alodine on top of that.
That would add one more rinse cycle, and do a chemical conversion
of that top layer too. And of course, a great rinse again.
Anyway, I doubt the tanks are toast....but you'd do well to
get them cleaned and treated up, and then be good to them
from then on...keep them nice and dry...maybe buy some
dessicant cartridges that you can attach. And then finally
get them full of fuel later.
Without seeing it first hand though, it's tough to say the
answer with any certainty.
Tim Olson - RV-10 N104CD - Flying
do not archive
Jeff Carpenter wrote:
| Quote: | I asked this question over 24 hours ago and so far there have been no
responses. With all that's going on with the list right now I'm going
to repost the question, with the attached picture in the hopes I might
get some feedback. Where's John Cox when you need him?
When I made my tanks... last May and June... I taped off the areas of
the skin that would be mated to the stiffeners and ribs with blue
painters tape. I roughened up the surface with scotch brite, cleaned
with aluma-prep and assembled with pro-seal. I left the baffle off of
the tanks as I was debating the installation of capacitance senders
instead of the floats. Over time (can't quite say how much) I pulled up
the painters tape.
So, I'm now ready to close up the tanks (with the floats) and find that
the right tank has a light corrosion in it... primarily under the areas
and at the edges of where the tape had been. I believe this is both
from the adhesive on the tape as well as my failure to completely rinse
the aluma-prep off in some areas. I can remove this with a whole lot of
elbow grease and a scotch brite pad. It comes up a bit easier with
aluma-prep and a scotch brite pad, but will then run in to the nooks and
crannies of the tank and create a new problem somewhere else if I don't
rinse quickly enough.
Will the presence of fuel in the tank act as corrosion protection and
keep this from progressing? Is this process something that stops when
the corrosive agent (the aluma prep, or the tape) is removed or "used
up," or is this a ball that once rolling won't stop?
Jeff Carpenter
40304
Scoth brite Hell
Awaiting your reply
------------------------------------------------------------------------
IMG_0257.JPG
<pre><b><font size color="#000000" face="courier new,courier">
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href="http://www.matronics.com/contribution">http://www.matronics.com/contribution</a>
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nicholscatoauto(at)aol.co
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| Posted: Wed Mar 12, 2008 7:33 am Post subject: Fuel Tank Corrosion, with visual aid |
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While we are on the fuel tank topic John Cox brings up a good point about alcohol and its effects on proseal. I am about 4 weeks away from starting my fuel tanks and would really like to build the entire fuel system to accept a moderate amount of alcohol, say 10%. Is anybody else taking a proactive approach to possibly using fuel with alcohol in it. Not that I would use it as a general rule but it would always be an option if needed. If anyone has any insight or thoughts fire away.
Jeff Nichols
40648
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jeff(at)westcottpress.com
Guest
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| Posted: Wed Mar 12, 2008 9:10 am Post subject: Fuel Tank Corrosion, with visual aid |
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Thank you John and all who responded. I've bit the bullet. New
right fuel tank parts were ordered this morning and will ship with my
finish kit next week. I can only stand so much work with scotch
brite pads and magnifying glasses. I'm about $460 lighter in the
wallet, but I think starting over will be faster and it's hard to put
a price on peace of mind.
Jeff Carpenter
40304
Do Not Archive
On Mar 11, 2008, at 6:43 PM, John W. Cox wrote:
[quote]
<johnwcox(at)pacificnw.com>
I'm undergoing knee surgery tomorrow and still a bit heavy hearted
over
the loss of a fellow member and what I ranked as one of the five
prettiest RV-10s ever completed. Damn it!
Aluma-prep uses acid to etch and make porous the Alclad finish.
(and did
you know there is a top side and bottom side finish with visible grain
direction.) It is important in pursuit of a quality finish job that
the
substrate be clean before application of aluma-prep. It is
important to
neutralize the acid with de-ionized or distilled water. Think of the
acid as only a catalyst. Once the reaction begins, you need to
remediate and finish the process. The Alodine treatment is chromic
acid
which hardens the porous finish. The final step is to wash again with
Non mineralized water. Often, builders use tap water and introduce
contaminants into the chemistry. (Anyone watching all the
pharmaceuticals being found in common tap water?) The porous
characteristic aides in later primer or sealer application with long
term adhesion. Remember that each side of the Alclad only has 5% pure
aluminum to turn whitish with oxidation. (You do the math on 0.016 or
0.032 sheet stock). To sand, scotchbrite or acid etch it too much
is to
go right through to the copper hybrid under the pure aluminum. (It
alodines differently). Most Structural Repair Manuals spell out
replacement of base material when corrosion reaches 10% of original
thickness. That is why as the builder, we need to create our own
SRM and
know the thickness of all materials we chose to use in assemblage.
Just
because it came from VANS does not justify guessing later. When
corrosion is found, it must be 100% removed or just like a cavity, it
just keeps feeding itself. If we have to remediate beyond 10%, its
off
for a new part(at the airlines). I don't think that is what you
want to
hear. We often use MEK with proper skin protection to remove
contaminates and organics before re-alodining aluminum. Yes we do,
re-alodine. Every exposed piece gets the treatment.
One of the premises yet to be answered is how does "my beloved
proseal"
hold up to adulterated corn squeezing inside the fuel tank. I would
love for the discussion to get elevated as to which components need to
be replaced to embrace subsidizing American Farmers instead of
importation of $110+ per barrel crude and amplify our balance of trade
deficit to Third World Tycoons. How about our President opening
the US
strategic oil reserves to wipe out all of the US hedge fund investors
who are making this situation worse by pumping up artificial demand.
Fuel in the tank acts to reduce airborne oxidants but does not
eliminate
them. That is the old wives tale of keep tanks topped off. The ball
will stop rolling when it is removed from the playing field. It
doesn't
stop on its own. Sorry.
Study Intergranular and Exfoliation Corrosion.
"http://aluminium.matter.org.uk/content/html/eng/default.asp?
catid=180&p
ageid 144416690" Use at least a 5X loop or 10X loop to view the
degree
of corrosion remaining.
John Cox
40600
Pegleg Hell in Portland
--
| | - The Matronics RV10-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?RV10-List |
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