corrosion protection - Dupont Products

Charles Skorupa · Post by **Charles Skorupa** » Fri Feb 17, 2012 5:46 pm

I think the main reason for putting the parts together wet is to help
prevent or reduce crevice corrosion since the interfacing surfaces gap will
be filled. Crevice corrosion greatly increases the rate of corrosion. I
think Boeing assembles some joints wet as faying surface seal in certain
locations prone to catch moisture for that reason. Might also help keep any
rain or spray that got past the rivets or wherever from spreading along the
interfacing surfaces via capillary action. Gotta dip those rivets, too! I
also seem to remember a few skin seams on the fuselage that annoy me because
the overlap is facing up vs. down so moisture can naturally drain into the
joint. Chuck Bailey used a marine sealant on his skin joints to prevent
this. I am positive that any adhesive benefits are not included in strength
calculations. At best, some may consider it added margin. If that makes
them feel better, who am I to argue.

Of course, as always, I could be wrong!

- Chuck Skorupa _
(retire in 1 week to finally get serious about finishing Rebel Elite S/N
500)
----- Original Message -----
From: McClary, Terry (GEAE) <Terry.McClary@ae.ge.com>
To: <murphy-rebel@dcsol.com>
Sent: Thursday, April 20, 2000 8:49 AM
Subject: RE: corrosion protection - Dupont Products

<<snip>>
I didn't plan on putting the parts together wet. Having worked in a

production

facility and now supporting an overhaul shop, I know on a production basis

it

would be damn near, if not impossible, to assemble on a "wet" basis. I'm

with

you in hoping the design margins aren't close enough to require the

"adhesive

margin."
<<snip>>

Terry

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McClary, Terry (GEAE) · Post by **McClary, Terry (GEAE)** » Fri Feb 17, 2012 5:46 pm

David,

Thanks for the detailed response. I bought the float attach kit also so I had
decided to prime all interior surfaces. Sure are a lot of opinions on this
matter. What really clinched it for me was an FAA safety meeting at a local
airport that has a fleet of DC-3's based there. They offered the opportunity to
climb through the interior and when I looked at all the primed surfaces I
decided if it was good enough for the DC-3 with all the years they have been
around, it was good enough for me. (Before I get a lot of response, I'll
acknowledge that the aluminum in the DC-3 was probably not 6061 but I like to
error on the conservative side.)

Either primer system requires a breathing system for spray application. I
looked for breathing system ideas at Sun N Fun but only found commercial
products at a minimum of $350 USD. I had read your previous note on the
Canadian Tire hoods, and not having Canadian Tires in the US, I checked the
price of commercial hoods, about $75 USD. I am a member of a volunteer fire
department so I am going ask if they have any old SCBA hoods around. Your
vacuum motor air supply is a good idea though I talked to one fellow who was
using the smog pump from an old car he had as the supply. Might be a little
quieter.

I didn't plan on putting the parts together wet. Having worked in a production
facility and now supporting an overhaul shop, I know on a production basis it
would be damn near, if not impossible, to assemble on a "wet" basis. I'm with
you in hoping the design margins aren't close enough to require the "adhesive
margin."

A friend gave me an old furnace blower and motor. I just need to be home long
enough to build a paint booth. I'm going to build it out of plastic and suspend
it from the ceiling in the garage. I figure I can pull the booth to the ceiling
to get it out of the way if I need the space.

On your workspace comment, my son swears that I built my house around my, at the
time, planned project. I bought the lot my house is on because I could have a
walk out basement. Then I had double opening doors installed to the outside
world.

Terry

-----Original Message-----
From: David A. Ricker [mailto:ricker@dbis.ns.ca]
Sent: Thursday, April 20, 2000 11:11 AM
To: (Murphy Rebel Builders List)
Subject: Re: corrosion protection - Dupont Products

Terry

On Elite #583 we are using Dupont Corlar filling wash primer. This is available
in chromate bearing (820R) and non-chromate formulation (810R), we are using the
chromate version. When you use the chromate version they say you do NOT need to
apply a chromic conversion treatment (Alodyne/Iridite). This is a big plus for
us since we do not want the problems associated with disposing with the
hazardous waste from the process. When I looked into it, being above board (and
convincing raw material suppliers to sell you the material in bulk at a
reasonable price) would have required being certified to handle the material and
using approved disposal services (unless it went down the drain but having a
septic system and a well rules that out even if your concience doesn't). Local
service providers were not capable of providing the irridite service to our
satisfaction either. BTW, Alodyne = Iridite, these are trade names for chromic
conversion treatment chemicals, Alodyne is the name you hear around aircraft &
Iridite is what you hear around elelctronic chassis/sheet metal fab shops.

Back to Corlar, this material is used in local aircraft refinishing and float
manufacturing facilities. I suppose they have a good handle on corrosion issues
in this area due to the proximity of the salty Atlantic Ocean....... I first
got a lead on using this material by reading the RV archives. I guess I should
also mention that we are building with the possibility of putting this plane on
floats at some pooint so we wanted to apply some corrosion protection to all of
the internal surfaces and procuring the Poly F product in that quantity was
going to be a royal pain so we went looking for locally sourced alternatives

As for application, the Murphy instructions say you should assemble the parts
wet implying to "glue" the parts together (with the Poly F product), in our case
that was not consistent with our basement assembly area (fumes) so we assemble
after the parts dry with the exception of dipping the rivets. I call on two
reasons for believing this is adequate, first I cannot believe Murphy would
design the structure so close to the edge that the "adhesive" properties of the
paint would make a pass/fail difference on the strength of the structure and the
fact that I spoke to a tech person at Cessna who told me that they assemble
their aircraft "dry" after all the piece parts are alodyne/iridite treated and
painted.

We contacted the Dupont Tech center (Ontario?) to get advice on this. It is
recommended to follow the Corlar with a high solids urethane primer 1020R
(Ochre) or 1044R (Gray), and a Dupont topcoat like Imron. They also said we
should be able to get good advice from their re-sellers like UAP but we felt
speaking to "the horses mouth" would provide the best information. We got the
requisite data sheets (including application instructions and MSDSs from the
local UAP.

These Dupont products are available at your local UAP auto body supply jobber -
off the shelf, no HAZMAT shipping issues.

Dupont is clear on their direction to use a paint "system" from ONE manufacturer
to avoid incompatibility.

Application of all these products must done with a fresh air supply to the
painter since these days just about every paint you will encounter will have
very nasty chemicals like isocyanates (or chromate in typical zinc chromate) in
them. Normal charcoal etc. masks are NOT adequate for these paints. Your fresh
air system does not need to be expensive, ours is just a shop vac located in a
room
outside the painting area to supply air to the painter and an old furnace blower
which exhausts the paint fumes and maintains the shop at a pressure lower than
ambient. This ensures that fumes won't enter the house attached to the workshop
(that is a description of
priorities isn't it!). You will need a hood/visor to pump the air into, we made
one from a Canadian Tire clear visor and some fabric or you can spend more $ for
an official version.

As we did, you should look at the alternatives and satisfy yourself that the
decisions you make are best for your situation. Our choices were made based on
our needs and imposed restrictions and hopefully we have made good ones!

Hope all this is useful,

Dave R.

McClary, Terry (GEAE) wrote:

Dave R.,

Care to share where you got your recommendations on which DuPont products to
use? Did you use a web site, local dealer, or user recommendations to determine

which is the best product for the application and how to apply.

I've bought a quart of the Poly Fiber primer and the associated pre-prime
chemicals. I also talked to the distributors at Sun N Fun about pre-prime
cleaning and primer application. The Poly Fiber factory was very helpful and
fast about providing MSDS sheets and answering questions by telephone, but, I
didn't ask for any of the details you did.

I know a couple of the fellows in my EAA chapter have talked about using DuPont
products on their projects. I decided to stay with the Murphy recommendation
but I haven't started priming. If DuPont supports their products better, maybe
I'll switch before I get started.

Terry

-----Original Message-----
From: David A. Ricker [ mailto:ricker@dbis.ns.ca <mailto:ricker@dbis.ns.ca> ]
Sent: Thursday, April 20, 2000 9:44 AM
To: (Murphy Rebel Builders List)
Subject: Re: corrosion protection

Ken, Bob

It looks like something changed (before we got our kit, about March '97). Our
package
says nothing about chromate and a quick call to Poly F confirms that there is no

chromate
in the product. The guy I talked to said they had put in some "miracle"
additive called
"hibosil" or" hiboseal". When pressed on how this worked (as in, does it form a

sacrificial anode like zinc chromate or does it simply improve adhesion) the guy

wouldn't
discuss it. Trade secret. For me that just confirms our decision to deal with
Dupont
who are willing to discuss their products and not give you the PR face.

FWIW, we are using a Dupont etching wash primer recommended for aluminum
(Corlar) which
has the option of chromate or not and is availible at your local auto parts
jobber (no
HAZMAT shipping issues). For the chromate version they specifically say
alodine/irridite
chromic conversion treatments are NOT required.

Hope this helps put more info in the hands of those that can use it.

Dave R.

klehman@albedo.net wrote:

Dave

FWIW my old can says "EP-420 Epoxy Chromate Primer". My brand new can says
simply "EP-420 Epoxy Primer". Sounds like something changed.

Ken

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--
David A. Ricker P. Eng.
DARTEC Engineering Inc.
Fall River, Nova Scotia
Canada, B2T 1E8
ricker@dbis.ns.ca

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--
David A. Ricker P. Eng.
DARTEC Engineering Inc.
Fall River, Nova Scotia
Canada, B2T 1E8
ricker@dbis.ns.ca

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David A. Ricker · Post by **David A. Ricker** » Fri Feb 17, 2012 5:46 pm

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> Terry
On Elite #583 we are using Dupont Corlar filling wash primer. This is available in chromate bearing (820R) and non-chromate formulation (810R), we are using the chromate version. When you use the chromate version they say you do NOT need to apply a chromic conversion treatment (Alodyne/Iridite). This is a big plus for us since we do not want the problems associated with disposing with the hazardous waste from the process. When I looked into it, being above board (and convincing raw material suppliers to sell you the material in bulk at a reasonable price) would have required being certified to handle the material and using approved disposal services (unless it went down the drain but having a septic system and a well rules that out even if your concience doesn't). Local service providers were not capable of providing the irridite service to our satisfaction either. BTW, Alodyne = Iridite, these are trade names for chromic conversion treatment chemicals, Alodyne is the name you hear around aircraft & Iridite is what you hear around elelctronic chassis/sheet metal fab shops.
Back to Corlar, this material is used in local aircraft refinishing and float manufacturing facilities. I suppose they have a good handle on corrosion issues in this area due to the proximity of the salty Atlantic Ocean....... I first got a lead on using this material by reading the RV archives. I guess I should also mention that we are building with the possibility of putting this plane on floats at some pooint so we wanted to apply some corrosion protection to all of the internal surfaces and procuring the Poly F product in that quantity was going to be a royal pain so we went looking for locally sourced alternatives
As for application, the Murphy instructions say you should assemble the parts wet implying to "glue" the parts together (with the Poly F product), in our case that was not consistent with our basement assembly area (fumes) so we assemble after the parts dry with the exception of dipping the rivets. I call on two reasons for believing this is adequate, first I cannot believe Murphy would design the structure so close to the edge that the "adhesive" properties of the paint would make a pass/fail difference on the strength of the structure and the fact that I spoke to a tech person at Cessna who told me that they assemble their aircraft "dry" after all the piece parts are alodyne/iridite treated and painted.
We contacted the Dupont Tech center (Ontario?) to get advice on this. It is recommended to follow the Corlar with a high solids urethane primer 1020R (Ochre) or 1044R (Gray), and a Dupont topcoat like Imron. They also said we should be able to get good advice from their re-sellers like UAP but we felt speaking to "the horses mouth" would provide the best information. We got the requisite data sheets (including application instructions and MSDSs from the local UAP.
These Dupont products are available at your local UAP auto body supply jobber - off the shelf, no HAZMAT shipping issues.
Dupont is clear on their direction to use a paint "system" from ONE manufacturer to avoid incompatibility.
Application of all these products must done with a fresh air supply to the painter since these days just about every paint you will encounter will have very nasty chemicals like isocyanates (or chromate in typical zinc chromate) in them. Normal charcoal etc. masks are NOT adequate for these paints. Your fresh air system does not need to be expensive, ours is just a shop vac located in a room
outside the painting area to supply air to the painter and an old furnace blower which exhausts the paint fumes and maintains the shop at a pressure lower than ambient. This ensures that fumes won't enter the house attached to the workshop (that is a description of
priorities isn't it!). You will need a hood/visor to pump the air into, we made one from a Canadian Tire clear visor and some fabric or you can spend more $ for an official version.
As we did, you should look at the alternatives and satisfy yourself that the decisions you make are best for your situation. Our choices were made based on our needs and imposed restrictions and hopefully we have made good ones!
Hope all this is useful,
Dave R.
McClary, Terry (GEAE) wrote:

Dave R.,
Care to share where you got your recommendations on which DuPont products to
use? Did you use a web site, local dealer, or user recommendations to determine
which is the best product for the application and how to apply.
I've bought a quart of the Poly Fiber primer and the associated pre-prime
chemicals. I also talked to the distributors at Sun N Fun about pre-prime
cleaning and primer application. The Poly Fiber factory was very helpful and
fast about providing MSDS sheets and answering questions by telephone, but, I
didn't ask for any of the details you did.
I know a couple of the fellows in my EAA chapter have talked about using DuPont
products on their projects. I decided to stay with the Murphy recommendation
but I haven't started priming. If DuPont supports their products better, maybe
I'll switch before I get started.
Terry
-----Original Message-----
From: David A. Ricker [mailto:ricker@dbis.ns.ca (ricker@dbis.ns.ca)]
Sent: Thursday, April 20, 2000 9:44 AM
To: (Murphy Rebel Builders List)
Subject: Re: corrosion protection
Ken, Bob
It looks like something changed (before we got our kit, about March '97). Our
package
says nothing about chromate and a quick call to Poly F confirms that there is no
chromate
in the product. The guy I talked to said they had put in some "miracle"
additive called
"hibosil" or" hiboseal". When pressed on how this worked (as in, does it form a
sacrificial anode like zinc chromate or does it simply improve adhesion) the guy
wouldn't
discuss it. Trade secret. For me that just confirms our decision to deal with
Dupont
who are willing to discuss their products and not give you the PR face.
FWIW, we are using a Dupont etching wash primer recommended for aluminum
(Corlar) which
has the option of chromate or not and is availible at your local auto parts
jobber (no
HAZMAT shipping issues). For the chromate version they specifically say
alodine/irridite
chromic conversion treatments are NOT required.
Hope this helps put more info in the hands of those that can use it.
Dave R.
klehman@albedo.net wrote:
Dave

FWIW my old can says "EP-420 Epoxy Chromate Primer". My brand new can says
simply "EP-420 Epoxy Primer". Sounds like something changed.

Ken

*-------------------------------------------------------------------------------
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between builders and owners of Murphy Rebel aircraft.
Archives located at:
http://www.dcsol.com/murphy-rebel/lists/default.htm

*-------------------------------------------------------------------------------
----*
--
David A. Ricker P. Eng.
DARTEC Engineering Inc.
Fall River, Nova Scotia
Canada, B2T 1E8
ricker@dbis.ns.ca
*-------------------------------------------------------------------------------
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The Murphy Rebel Builders List is for the discussion
between builders and owners of Murphy Rebel aircraft.
Archives located at:
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*-------------------------------------------------------------------------------
----*
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The Murphy Rebel Builders List is for the discussion
between builders and owners of Murphy Rebel aircraft.
Archives located at:
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*-----------------------------------------------------------------------------------*

--
David A. Ricker P. Eng.
DARTEC Engineering Inc.
Fall River, Nova Scotia
Canada, B2T 1E8
ricker@dbis.ns.ca

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David A. Ricker · Post by **David A. Ricker** » Fri Feb 17, 2012 5:46 pm

Terry

Yeah, you are right about there being many opinions, leaves it up to us to sift through
it all & decide what is best for your case. Hope I haven't added too much confusion!

I think you are right that the treatment in the DC-3 is a goood example of what you can
have with a bit of care. Last weekend I happened to be at a local aviation museum and
saw the wing of a WW II vintage flying boat, perhaps a Canso? and it was nicely primed
inside and didn't appear to be in bad shape other than being a bit bent. I think it was
landed in a peat bog & left for many years. I think the worst problems will be in the
concealed nooks & crannies where moisture can collect & cause problems, it certainly is
that way with steel cars so doing things that are a bit conservative probably is a good
thing.

The shield I mentioned from Canadian Tire is just a flip up plastic safety shield to keep
things out of your eyes when you are grinding or turning things on a wood lathe or things
like that. It looks somrthing like an arc welding mask/shield. We just built a hood to
enclose your head & contain the fresh air, makeshift but it works OK until we come up
with something better.

On assembling wet, I can just picture trying to put a wing skin on wet without having it
dry before you get it in place and put a few riets in but then I haven't tried that
either.

OK, gotta run

Dave R.

McClary, Terry (GEAE) wrote:

David,

Thanks for the detailed response. I bought the float attach kit also so I had
decided to prime all interior surfaces. Sure are a lot of opinions on this
matter. What really clinched it for me was an FAA safety meeting at a local
airport that has a fleet of DC-3's based there. They offered the opportunity to
climb through the interior and when I looked at all the primed surfaces I
decided if it was good enough for the DC-3 with all the years they have been
around, it was good enough for me. (Before I get a lot of response, I'll
acknowledge that the aluminum in the DC-3 was probably not 6061 but I like to
error on the conservative side.)

Either primer system requires a breathing system for spray application. I
looked for breathing system ideas at Sun N Fun but only found commercial
products at a minimum of $350 USD. I had read your previous note on the
Canadian Tire hoods, and not having Canadian Tires in the US, I checked the
price of commercial hoods, about $75 USD. I am a member of a volunteer fire
department so I am going ask if they have any old SCBA hoods around. Your
vacuum motor air supply is a good idea though I talked to one fellow who was
using the smog pump from an old car he had as the supply. Might be a little
quieter.

I didn't plan on putting the parts together wet. Having worked in a production
facility and now supporting an overhaul shop, I know on a production basis it
would be damn near, if not impossible, to assemble on a "wet" basis. I'm with
you in hoping the design margins aren't close enough to require the "adhesive
margin."

A friend gave me an old furnace blower and motor. I just need to be home long
enough to build a paint booth. I'm going to build it out of plastic and suspend
it from the ceiling in the garage. I figure I can pull the booth to the ceiling
to get it out of the way if I need the space.

On your workspace comment, my son swears that I built my house around my, at the
time, planned project. I bought the lot my house is on because I could have a
walk out basement. Then I had double opening doors installed to the outside
world.

Terry

-----Original Message-----
From: David A. Ricker [mailto:ricker@dbis.ns.ca]
Sent: Thursday, April 20, 2000 11:11 AM
To: (Murphy Rebel Builders List)
Subject: Re: corrosion protection - Dupont Products

Terry

On Elite #583 we are using Dupont Corlar filling wash primer. This is available
in chromate bearing (820R) and non-chromate formulation (810R), we are using the
chromate version. When you use the chromate version they say you do NOT need to
apply a chromic conversion treatment (Alodyne/Iridite). This is a big plus for

SNIP!

--
David A. Ricker P. Eng.
DARTEC Engineering Inc.
Fall River, Nova Scotia
Canada, B2T 1E8
ricker@dbis.ns.ca

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Bob Patterson · Post by **Bob Patterson** » Fri Feb 17, 2012 5:46 pm

Dave,
Not sure what quantity of PolyFibre Primer you envisioned needing,
but <2 quarts> is sufficient to coat all of the interior surfaces of a
Rebel (just ask Jim Albright - his is finished !). A thin coat is all
that is needed/desirable. Alodyne treatment is not required before the
application of the primer.

The idea of putting parts together wet was partly to gain bonding
strength (which was NOT a part of stress calculations, but Nice To Have),
but mostly to ensure that the gap between pieces was filled, to prevent
capillary action from pulling water in. PolyFiber should give at least a
couple of hours working time in a cool shop - lots of time to drop a wing
skin into place & insert a few clecoes....

Corlar sounds like it might be an interesting solution. I assume
it is an epoxy or enamel product... How long has it been used in aircraft
(and float) applications ? How much weight will it add to a finished
Rebel ?

I'm surprised that they recommend a Urethane top coat, as the
paint shops I've spoken to all say that Urethane looks nice, but is POROUS,
so water goes right through & produces corrosion. (That's why nobody here
uses Urethane paint on floats anymore - at least, not without a good coat
of epoxy primer first...) This would mean that the Corlar is really all
the protection you get .....

.....bobp

-----------------------------orig.-----------------------------------------
At 12:10 PM 4/20/00 -0300, you wrote:

Terry

On Elite #583 we are using Dupont Corlar filling wash primer. This is

available in

chromate bearing (820R) and non-chromate formulation (810R), we are using

the chromate

version. When you use the chromate version they say you do NOT need to

apply a chromic

conversion treatment (Alodyne/Iridite). This is a big plus for us since we

do not want

the problems associated with disposing with the hazardous waste from the

process. When I

looked into it, being above board (and convincing raw material suppliers to

sell you the

material in bulk at a reasonable price) would have required being certified

to handle the

material and using approved disposal services (unless it went down the

drain but having a

septic system and a well rules that out even if your concience doesn't).

Local service

providers were not capable of providing the irridite service to our

satisfaction either.

BTW, Alodyne = Iridite, these are trade names for chromic conversion treatment
chemicals, Alodyne is the name you hear around aircraft & Iridite is what

you hear around

elelctronic chassis/sheet metal fab shops.

Back to Corlar, this material is used in local aircraft refinishing and float
manufacturing facilities. I suppose they have a good handle on corrosion

issues in this

area due to the proximity of the salty Atlantic Ocean....... I first got a

lead on using

this material by reading the RV archives. I guess I should also mention

that we are

building with the possibility of putting this plane on floats at some

pooint so we wanted

to apply some corrosion protection to all of the internal surfaces and

procuring the Poly

F product in that quantity was going to be a royal pain so we went looking

for locally

sourced alternatives

As for application, the Murphy instructions say you should assemble the

parts wet

implying to "glue" the parts together (with the Poly F product), in our

case that was not

consistent with our basement assembly area (fumes) so we assemble after the

parts dry

with the exception of dipping the rivets. I call on two reasons for

believing this is

adequate, first I cannot believe Murphy would design the structure so close

to the edge

that the "adhesive" properties of the paint would make a pass/fail

difference on the

strength of the structure and the fact that I spoke to a tech person at

Cessna who told

me that they assemble their aircraft "dry" after all the piece parts are

alodyne/iridite

treated and painted.

We contacted the Dupont Tech center (Ontario?) to get advice on this. It

is recommended

to follow the Corlar with a high solids urethane primer 1020R (Ochre) or

1044R (Gray),

and a Dupont topcoat like Imron. They also said we should be able to get

good advice

from their re-sellers like UAP but we felt speaking to "the horses mouth"

would provide

the best information. We got the requisite data sheets (including application
instructions and MSDSs from the local UAP.

These Dupont products are available at your local UAP auto body supply

jobber - off the

shelf, no HAZMAT shipping issues.

Dupont is clear on their direction to use a paint "system" from ONE

manufacturer to avoid

incompatibility.

Application of all these products must done with a fresh air supply to the

painter since

these days just about every paint you will encounter will have very nasty

chemicals like

isocyanates (or chromate in typical zinc chromate) in them. Normal

charcoal etc. masks

are NOT adequate for these paints. Your fresh air system does not need to

be expensive,

ours is just a shop vac located in a room
outside the painting area to supply air to the painter and an old furnace

blower which

exhausts the paint fumes and maintains the shop at a pressure lower than

ambient. This

ensures that fumes won't enter the house attached to the workshop (that is

a description

of
priorities isn't it!). You will need a hood/visor to pump the air into, we

made one from

a Canadian Tire clear visor and some fabric or you can spend more $ for an

official

version.

As we did, you should look at the alternatives and satisfy yourself that

the decisions

you make are best for your situation. Our choices were made based on our

needs and

imposed restrictions and hopefully we have made good ones!

Hope all this is useful,

Dave R.

McClary, Terry (GEAE) wrote:

Dave R.,

Care to share where you got your recommendations on which DuPont products to
use? Did you use a web site, local dealer, or user recommendations to

determine

which is the best product for the application and how to apply.

I've bought a quart of the Poly Fiber primer and the associated pre-prime
chemicals. I also talked to the distributors at Sun N Fun about pre-prime
cleaning and primer application. The Poly Fiber factory was very helpful and
fast about providing MSDS sheets and answering questions by telephone, but, I
didn't ask for any of the details you did.

I know a couple of the fellows in my EAA chapter have talked about using

DuPont

products on their projects. I decided to stay with the Murphy recommendation
but I haven't started priming. If DuPont supports their products better,

maybe

I'll switch before I get started.

Terry

-----Original Message-----
From: David A. Ricker [mailto:ricker@dbis.ns.ca]
Sent: Thursday, April 20, 2000 9:44 AM
To: (Murphy Rebel Builders List)
Subject: Re: corrosion protection

Ken, Bob

It looks like something changed (before we got our kit, about March '97).

Our

package
says nothing about chromate and a quick call to Poly F confirms that

there is no

chromate
in the product. The guy I talked to said they had put in some "miracle"
additive called
"hibosil" or" hiboseal". When pressed on how this worked (as in, does it

form a

sacrificial anode like zinc chromate or does it simply improve adhesion)

the guy

wouldn't
discuss it. Trade secret. For me that just confirms our decision to

deal with

Dupont
who are willing to discuss their products and not give you the PR face.

FWIW, we are using a Dupont etching wash primer recommended for aluminum
(Corlar) which
has the option of chromate or not and is availible at your local auto parts
jobber (no
HAZMAT shipping issues). For the chromate version they specifically say
alodine/irridite
chromic conversion treatments are NOT required.

Hope this helps put more info in the hands of those that can use it.

Dave R.

klehman@albedo.net wrote:

Dave

FWIW my old can says "EP-420 Epoxy Chromate Primer". My brand new can says
simply "EP-420 Epoxy Primer". Sounds like something changed.

Ken

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DARTEC Engineering Inc.
Fall River, Nova Scotia
Canada, B2T 1E8
ricker@dbis.ns.ca

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DARTEC Engineering Inc.
Fall River, Nova Scotia
Canada, B2T 1E8
ricker@dbis.ns.ca

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML>
Terry
On Elite #583 we are using Dupont Corlar filling wash primer. 
This is available in chromate bearing (820R) and non-chromate formulation
(810R), we are using the chromate version. When you use the chromate version
they say you do NOT need to apply a chromic conversion treatment

(Alodyne/Iridite). 

This is a big plus for us since we do not want the problems associated
with disposing with the hazardous waste from the process.  When I
looked into it, being above board (and convincing raw material suppliers
to sell you the material in bulk at a reasonable price) would have required
being certified to handle the material and using approved disposal services
(unless it went down the drain but having a septic system and a well rules
that out even if your concience doesn't).  Local service providers
were not capable of providing the irridite service to our satisfaction
either.  BTW, Alodyne =  Iridite, these are trade names for chromic
conversion treatment chemicals, Alodyne is the name you hear around aircraft
& Iridite is what you hear around elelctronic chassis/sheet metal fab
shops.
Back to Corlar, this material is used in local aircraft refinishing
and float manufacturing facilities.  I suppose they have a good handle
on corrosion issues in this area due to the proximity of the salty Atlantic
Ocean.......  I first got a lead on using this material by reading
the RV archives.  I guess I should also mention that we are building
with the possibility of putting this plane on floats at some pooint so
we wanted to apply some corrosion protection to all of the internal surfaces
and procuring the Poly F product in that quantity was going to be a royal
pain so we went looking for locally sourced alternatives
As for application, the Murphy instructions say you should assemble
the parts wet implying to "glue" the parts together (with the Poly F product),
in our case that was not consistent with our basement assembly area (fumes)
so we assemble after the parts dry with the exception of dipping the

rivets. 

I call on two reasons for believing this is adequate, first I cannot believe
Murphy would design the structure so close to the edge that the "adhesive"
properties of the paint would make a pass/fail difference on the strength
of the structure and the fact that I spoke to a tech person at Cessna who
told me that they assemble their aircraft "dry" after all the piece parts
are alodyne/iridite treated and painted.
We contacted the Dupont Tech center (Ontario?) to get advice on this. 
It is recommended to follow the Corlar with a high solids urethane primer
1020R (Ochre) or 1044R (Gray), and a Dupont topcoat like Imron.  They
also said we should be able to get good advice from their re-sellers like
UAP but we felt speaking to "the horses mouth" would provide the best

information. 

We got the requisite data sheets (including application instructions and
MSDSs from the local UAP.
These Dupont products are available at your local UAP auto body supply
jobber - off the shelf, no HAZMAT shipping issues.
Dupont is clear on their direction to use a paint "system" from ONE
manufacturer to avoid incompatibility.
Application of all these products must done with a fresh air
supply to the painter since these days just about every paint you
will encounter will have very nasty chemicals like isocyanates (or chromate
in typical zinc chromate) in them.  Normal charcoal etc. masks are
NOT adequate for these paints.  Your fresh air system does not need
to be expensive, ours is just a shop vac located in a room
 outside the painting area to supply air to the painter and an old furnace
blower which exhausts the paint fumes and maintains the shop at a pressure
lower than ambient.  This ensures that fumes won't enter the house
attached to the workshop (that is a description of
 priorities isn't it!).  You will need a hood/visor to pump the
air into, we made one from a Canadian Tire clear visor and some fabric
or you can spend more $ for an official version.
As we did, you should look at the alternatives and satisfy yourself
that the decisions you make are best for your situation.  Our choices
were made based on our needs and imposed restrictions and hopefully we
have made good ones!
Hope all this is useful,
Dave R.
McClary, Terry (GEAE) wrote:
<BLOCKQUOTE TYPE=CITE>Dave R.,
Care to share where you got your recommendations on which DuPont products
to
 use?  Did you use a web site, local dealer, or user recommendations
to determine
 which is the best product for the application and how to apply.
I've bought a quart of the Poly Fiber primer and the associated pre-prime
 chemicals.  I also talked to the distributors at Sun N Fun about
pre-prime
 cleaning and primer application.  The Poly Fiber factory was very
helpful and
 fast about providing MSDS sheets and answering questions by telephone,
but, I
 didn't ask for any of the details you did.
I know a couple of the fellows in my EAA chapter have talked about using
DuPont
 products on their projects.  I decided to stay with the Murphy
recommendation
 but I haven't started priming.  If DuPont supports their products
better, maybe
 I'll switch before I get started.
Terry
-----Original Message-----
 From: David A. Ricker [<A

HREF="mailto:ricker@dbis.ns.ca">mailto:ricker@dbis.ns.ca</A>]

Sent: Thursday, April 20, 2000 9:44 AM
 To: (Murphy Rebel Builders List)
 Subject: Re: corrosion protection
Ken, Bob
It looks like something changed (before we got our kit, about March
'97).  Our
 package
 says nothing about chromate and a quick call to Poly F confirms that
there is no
 chromate
 in the product.  The guy I talked to said they had put in some
"miracle"
 additive called
 "hibosil" or" hiboseal".  When pressed on how this worked (as
in, does it form a
 sacrificial anode like zinc chromate or does it simply improve adhesion)
the guy
 wouldn't
 discuss it.  Trade secret.  For me that just confirms our
decision to deal with
 Dupont
 who are willing to discuss their products and not give you the PR face.
FWIW, we are using a Dupont etching wash primer recommended for aluminum
 (Corlar) which
 has the option of chromate or not and is availible at your local auto
parts
 jobber (no
 HAZMAT shipping issues).  For the chromate version they specifically
say
 alodine/irridite
 chromic conversion treatments are NOT required.
Hope this helps put more info in the hands of those that can use it.
Dave R.
klehman@albedo.net wrote:
> Dave
 >
 > FWIW my old can says "EP-420 Epoxy Chromate Primer". My brand new
can says
 > simply "EP-420 Epoxy Primer". Sounds like something changed.
 >
 > Ken
 >
 *----------------------------------------------------------------------

---------

----*
 >  The Murphy Rebel Builders List is for the discussion
 >  between builders and owners of Murphy Rebel aircraft.
 >  Archives located at:
 >  <A

HREF="http://www.dcsol.com/murphy-rebel/lists ... /www.dcsol.
com/murphy-rebel/lists/default.htm</A>

>
 *----------------------------------------------------------------------

---------

----*
--
 David A. Ricker P. Eng.
 DARTEC Engineering Inc.
 Fall River, Nova Scotia
 Canada, B2T 1E8
 ricker@dbis.ns.ca
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  The Murphy Rebel Builders List is for the discussion
  between builders and owners of Murphy Rebel aircraft.
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*----------------------------------------------------------------------

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--
 David A. Ricker P. Eng.
 DARTEC Engineering Inc.
 Fall River, Nova Scotia
 Canada, B2T 1E8
 ricker@dbis.ns.ca
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David A. Ricker · Post by **David A. Ricker** » Fri Feb 17, 2012 5:46 pm

Chuck, group

Having a crevice will increase the risk of corrosion, I am not 100% certain of the
correct approach to avoid this though. If you assemble wet and you have any relative
movement of the joint to the extent that the paint layer between the metal delaminates
(from flexing of the joined structure, a distinct possibility) then you will have an
unprotected crevice for corrosion to start in. On the other hand if you paint and
assemble dry then you have a crevice but with both surfaces protected by their paint
layers.

I'm not sure which is better but for my circumstances we have gone with the latter since
we do not apply paint in our assembly area due to the fumes. Another justification if I
have to make a case is that Cessna does this also, for what that is worth.......

As for keeping water out of the structure, for the fuselage seams at least, we are
looking at using some sort of flexible sealing compound such as the much maligned proseal
or automotive seam sealer. The auto seam sealer looks like a good bet since it is
tenaciously sticky, remains flexible and is available off the shelf at your local
autobody jobber like UAP, no HAZMAT problems. It comes in caulking gun type tubes that
let you apply as little or as much as you want.

Well, there is my take on it, your mileage may vary :>)

Dave R.

PS Good to hear the Elite is progressing well, ours #583 is moving ahead slowly, been
hindered by this consulting thing.

Charles Skorupa wrote:

I think the main reason for putting the parts together wet is to help
prevent or reduce crevice corrosion since the interfacing surfaces gap will
be filled. Crevice corrosion greatly increases the rate of corrosion. I
think Boeing assembles some joints wet as faying surface seal in certain
locations prone to catch moisture for that reason. Might also help keep any
rain or spray that got past the rivets or wherever from spreading along the
interfacing surfaces via capillary action. Gotta dip those rivets, too! I
also seem to remember a few skin seams on the fuselage that annoy me because
the overlap is facing up vs. down so moisture can naturally drain into the
joint. Chuck Bailey used a marine sealant on his skin joints to prevent
this. I am positive that any adhesive benefits are not included in strength
calculations. At best, some may consider it added margin. If that makes
them feel better, who am I to argue.

Of course, as always, I could be wrong!

- Chuck Skorupa _
(retire in 1 week to finally get serious about finishing Rebel Elite S/N
500)
----- Original Message -----
From: McClary, Terry (GEAE) <Terry.McClary@ae.ge.com>
To: <murphy-rebel@dcsol.com>
Sent: Thursday, April 20, 2000 8:49 AM
Subject: RE: corrosion protection - Dupont Products

<<snip>>
I didn't plan on putting the parts together wet. Having worked in a
production
facility and now supporting an overhaul shop, I know on a production basis
it
would be damn near, if not impossible, to assemble on a "wet" basis. I'm
with
you in hoping the design margins aren't close enough to require the
"adhesive
margin."
<<snip>>

Terry

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David A. Ricker P. Eng.
DARTEC Engineering Inc.
Fall River, Nova Scotia
Canada, B2T 1E8
ricker@dbis.ns.ca

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David A. Ricker · Post by **David A. Ricker** » Fri Feb 17, 2012 5:46 pm

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> Bob
We looked at the merits of Poly F before getting deeply into the project and decided that for us, something sourced locally made more sense, we wanted one system for application to the inside and outside and at that point the explanation I had from Poly F about the constituents of their product didn't give me the same level of confidence as Duponts'. At that point PolyF had said the product was simply an epoxy primer without any other anti-corrosion properties. Recently I was advised they include something they call "hibosil" or "hiboseal" but they would not discuss the anti-corrosion mechanism - whether it was chemical or just made the paint stick, that didn't give me any more confidence in their product.
I have commented on the gap bonding/sealing issues in another posting today responding to Chuck S. so I'll refer you there for my take on that.
Corlar is a 2 part wash primer with the option of a zinc chromate constituent, I expect by definition that makes it an epoxy from the point of view that it comprises a "resin" (the paint) and an activator. It has the side benefit that it has a relatively long pot life, up to 72 hours. As far as how long it has been used on aircraft, that is a question I can't answer but I found a reference in the RV list archive dating back to 16 May 1995.
I don't have an official answer about the weight it adds to an airframe but it would depend really on how thick you apply it. In the literature I have, Dupont does not quote a weight or an application thickness, rather it states the thinning and air pressure rates. Prior to top coating, they recommend application of a high solids polyurethane primer (such as 1044R) following this with Imron polyurethane topcoat. It is important to use a system of compatible products for the prime/paint process to ensure correct adhesion - this from Dupont & other sources.
On the question of polyurethane porosity, I hadn't heard that before. It flies in the face of the advice I received from a multinational military aircraft R & O facility here which I consulted. They use an epoxy primer (MIL-P-23377) and polyurethane topcoat system made by Tempo Paint & Varnish in Weston , Ont. Tempo says "The Dura-Thane system is a Canadian manufactured and designed series of products engineered to provide the ultimate in the Aircraft coating field". I don't know more than that other than anecdotal information that Imron is really tough and used frequently on aircraft for that reason. Again we chose the Dupont product over Tempo because of availability issues but on the basis of similarity between the product descriptions.
Well, I hope this has added worth while information for the Rebel building community, this is a great forum to share what we learn during the building process.
Dave R.
Bob Patterson wrote:

Dave,
Not sure what quantity of PolyFibre Primer you envisioned needing,
but <2 quarts> is sufficient to coat all of the interior surfaces of a
Rebel (just ask Jim Albright - his is finished !). A thin coat is all
that is needed/desirable. Alodyne treatment is not required before the
application of the primer.
The idea of putting parts together wet was partly to gain bonding
strength (which was NOT a part of stress calculations, but Nice To Have),
but mostly to ensure that the gap between pieces was filled, to prevent
capillary action from pulling water in. PolyFiber should give at least a
couple of hours working time in a cool shop - lots of time to drop a wing
skin into place & insert a few clecoes....
Corlar sounds like it might be an interesting solution. I assume
it is an epoxy or enamel product... How long has it been used in aircraft
(and float) applications ? How much weight will it add to a finished
Rebel ?
I'm surprised that they recommend a Urethane top coat, as the
paint shops I've spoken to all say that Urethane looks nice, but is POROUS,
so water goes right through & produces corrosion. (That's why nobody here
uses Urethane paint on floats anymore - at least, not without a good coat
of epoxy primer first...) This would mean that the Corlar is really all
the protection you get .....
.....bobp

SNIP!
--
David A. Ricker P. Eng.
DARTEC Engineering Inc.
Fall River, Nova Scotia
Canada, B2T 1E8
ricker@dbis.ns.ca

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Bob Patterson · Post by **Bob Patterson** » Fri Feb 17, 2012 5:46 pm

Dave,
Sounds like we're both getting the same information. The paint
shops said that they will only use polyurethane paint IF they put a
solid, non-porous layer of epoxy primer UNDER IT.

You are absolutely correct in insisting on using a complete
paint "system" !! Wayne showed us a sample of the results of combining
primer & finishes from different manufacturers (and meant for different
uses) at our last Rebel Builders Meeting !! The finish on his sample
aileron covering just cracked and fell off in chunks, while the sample
done with the Stits (PolyFiber) system thoughout stayed tough and
solid, even when bent, folded, and mutilated !!! This mis-use of
combinations of finishes is what caused Steve Wittman's crash .....

One bit of useful information for the group - there is a good
sealant that should be safe for aircraft use:

It is an RTV Silicone that stays flexible, has good adhesion,
and DOESN'T produce corrosive acids when curing.
This IS NOT 'hardware store' stuff ! It is used to seal the
wire windings in electric motors, electrical connections, and automotive,
truck and trailer bodies, among other things.

It is part # SU 5007 RTV Silicone, from Silicones Unlimited Inc.,
in Marietta,GA (404) 578-1274. It comes in clear, white, gray/aluminum,
black, limestone, and bronze, in caulking gun type tubes. I have a full
data sheet here if anyone wants me to fax a copy. (or call me at
(905)457-5238)

Canadian distributor: Electro-Pulse Enterprises,
Burlington, Ontario L7P 3A7
Tel. (905) 336-7393 Fax: (905) 335-6462

Usually sold in case lots, at about $8-9/tube - might be able to
get a few tubes for folks if there is interest .....

......bobp

--------------------------------orig.------------------------------------------
At 01:43 PM 4/21/00 -0300, you wrote:

Bob

We looked at the merits of Poly F before getting deeply into the project

and decided that

for us, something sourced locally made more sense, we wanted one system for

application

to the inside and outside and at that point the explanation I had from Poly

F about the

constituents of their product didn't give me the same level of confidence

as Duponts'.

At that point PolyF had said the product was simply an epoxy primer without

any other

anti-corrosion properties. Recently I was advised they include something

they call

"hibosil" or "hiboseal" but they would not discuss the anti-corrosion

mechanism - whether

it was chemical or just made the paint stick, that didn't give me any more

confidence in

their product.

I have commented on the gap bonding/sealing issues in another posting today

responding to

Chuck S. so I'll refer you there for my take on that.

Corlar is a 2 part wash primer with the option of a zinc chromate

constituent, I expect

by definition that makes it an epoxy from the point of view that it

comprises a "resin"

(the paint) and an activator. It has the side benefit that it has a

relatively long pot

life, up to 72 hours. As far as how long it has been used on aircraft, that

is a question

I can't answer but I found a reference in the RV list archive dating back

to 16 May 1995.

I don't have an official answer about the weight it adds to an airframe but

it would

depend really on how thick you apply it. In the literature I have, Dupont

does not quote

a weight or an application thickness, rather it states the thinning and air

pressure

rates. Prior to top coating, they recommend application of a high solids

polyurethane

primer (such as 1044R) following this with Imron polyurethane topcoat. It

is important

to use a system of compatible products for the prime/paint process to

ensure correct

adhesion - this from Dupont & other sources.

On the question of polyurethane porosity, I hadn't heard that before. It

flies in the

face of the advice I received from a multinational military aircraft R & O

facility here

which I consulted. They use an epoxy primer (MIL-P-23377) and polyurethane

topcoat

system made by Tempo Paint & Varnish in Weston , Ont. Tempo says "The

Dura-Thane system

is a Canadian manufactured and designed series of products engineered to

provide the

ultimate in the Aircraft coating field". I don't know more than that other

than

anecdotal information that Imron is really tough and used frequently on

aircraft for that

reason. Again we chose the Dupont product over Tempo because of

availability issues but

on the basis of similarity between the product descriptions.

Well, I hope this has added worth while information for the Rebel building

community,

this is a great forum to share what we learn during the building process.

Dave R.

Bob Patterson wrote:

Dave,
Not sure what quantity of PolyFibre Primer you envisioned needing,
but <2 quarts> is sufficient to coat all of the interior surfaces of a
Rebel (just ask Jim Albright - his is finished !). A thin coat is all
that is needed/desirable. Alodyne treatment is not required before the
application of the primer.

The idea of putting parts together wet was partly to gain bonding
strength (which was NOT a part of stress calculations, but Nice To Have),
but mostly to ensure that the gap between pieces was filled, to prevent
capillary action from pulling water in. PolyFiber should give at least a
couple of hours working time in a cool shop - lots of time to drop a wing
skin into place & insert a few clecoes....

Corlar sounds like it might be an interesting solution. I assume
it is an epoxy or enamel product... How long has it been used in aircraft
(and float) applications ? How much weight will it add to a finished
Rebel ?

I'm surprised that they recommend a Urethane top coat, as the
paint shops I've spoken to all say that Urethane looks nice, but is POROUS,
so water goes right through & produces corrosion. (That's why nobody here
uses Urethane paint on floats anymore - at least, not without a good coat
of epoxy primer first...) This would mean that the Corlar is really all
the protection you get .....

.....bobp

SNIP!

--
David A. Ricker P. Eng.
DARTEC Engineering Inc.
Fall River, Nova Scotia
Canada, B2T 1E8
ricker@dbis.ns.ca

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML>
Bob
We looked at the merits of Poly F before getting deeply into the project
and decided that for us, something sourced locally made more sense, we
wanted one system for application to the inside and outside and at that
point the explanation I had from Poly F about the constituents of their
product didn't give me the same level of confidence as Duponts'. 
At that point PolyF had said the product was simply an epoxy primer without
any other anti-corrosion properties.  Recently I was advised they
include something they call "hibosil" or "hiboseal" but they would not
discuss the anti-corrosion mechanism - whether it was chemical or just
made the paint stick, that didn't give me any more confidence in their
product.
I have commented on the gap bonding/sealing issues in another posting
today responding to Chuck S. so I'll refer you there for my take on that.
Corlar is a 2 part wash primer with the option of a zinc chromate

constituent,

I expect by definition that makes it an epoxy from the point of view that
it comprises a "resin" (the paint) and an activator.  It has the side
benefit that it has a relatively long pot life, up to 72 hours. As far
as how long it has been used on aircraft, that is a question I can't answer
but I found a reference in the RV list archive dating back to 16 May 1995.
I don't have an official answer about the weight it adds to an airframe
but it would depend really on how thick you apply it.  In the literature
I have, Dupont does not quote a weight or an application thickness, rather
it states the thinning and air pressure rates.  Prior to top coating,
they recommend application of a high solids polyurethane primer (such as
1044R) following this with Imron polyurethane topcoat.  It is important
to use a system of compatible products for the prime/paint process to ensure
correct adhesion - this from Dupont & other sources.
On the question of polyurethane porosity, I hadn't heard that before. 
It flies in the face of the advice I received from a multinational military
aircraft R & O facility here which I consulted.  They use an epoxy
primer (MIL-P-23377) and polyurethane topcoat system made by Tempo
Paint & Varnish in Weston , Ont.  Tempo says "The Dura-Thane
system is a Canadian manufactured and designed series of products engineered
to provide the ultimate in the Aircraft coating field".  I don't
know more than that other than anecdotal information that Imron is really
tough and used frequently on aircraft for that reason.  Again we chose
the Dupont product over Tempo because of availability issues but on the
basis of similarity between the product descriptions.
Well, I hope this has added worth while information for the Rebel building
community, this is a great forum to share what we learn during the building
process.
Dave R.
Bob Patterson wrote:
<BLOCKQUOTE TYPE=CITE>Dave,
         Not sure what quantity of
PolyFibre Primer you envisioned needing,
 but <2 quarts> is sufficient to coat all of the interior surfaces
of a
 Rebel (just ask Jim Albright - his is finished !). A thin coat is all
 that is needed/desirable. Alodyne treatment is not required before
the
 application of the primer.
       The idea of putting parts together
wet was partly to gain bonding
 strength (which was NOT a part of stress calculations, but Nice To
Have),
 but mostly to ensure that the gap between pieces was filled, to prevent
 capillary action from pulling water in. PolyFiber should give at least
a
 couple of hours working time in a cool shop - lots of time to drop
a wing
 skin into place & insert a few clecoes....
        Corlar sounds like it might
be an interesting solution. I assume
 it is an epoxy or enamel product... How long has it been used in aircraft
 (and float) applications ?  How much weight will it add to a finished
 Rebel ?
        I'm surprised that they recommend
a Urethane top coat, as the
 paint shops I've spoken to all say that Urethane looks nice, but is
POROUS,
 so water goes right through & produces corrosion. (That's why nobody
here
 uses Urethane paint on floats anymore - at least, not without a good
coat
 of epoxy primer first...) This would mean that the Corlar is really
all
 the protection you get .....

            &nbs
p;            &n
bsp;         

.....bobp
  
  </BLOCKQUOTE>
SNIP!
--
 David A. Ricker P. Eng.
 DARTEC Engineering Inc.
 Fall River, Nova Scotia
 Canada, B2T 1E8
 ricker@dbis.ns.ca
  
  </HTML>

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Charles Skorupa · Post by **Charles Skorupa** » Fri Feb 17, 2012 5:46 pm

Dave,
Good food for thought. I wonder if we are missing the obvious. My boat is
submerged in salt water with all kinds of galvanic action going on due to
stray current (electrical type) at the moorage. Boat owners add zinc plates
to protect the submerged metal surfaces since zinc is more anodic that the
material it is protecting. So even if moisture got in the crevice, the zinc
in the zinc chromate primer would provide substantial level of protection.
Galvanic corrosion, crevice corrosion, oxygen depletion, lions and tigers
and bears, oh my! I'm getting scared to new levels of inactivity. Think
I'll just prime the surfaces, dip the rivets and call it good. If I can do
it wet, great. If not, oh well. I'll build another one in 30 years on my
85th birthday to replace the corroding hulk! Bet I forget about the whole
subject within 10 minutes of the first flight, though. Thanks for the great
suggestions.
- Chuck -

Having a crevice will increase the risk of corrosion, I am not 100%

certain of the

correct approach to avoid this though. If you assemble wet and you have

any relative

movement of the joint to the extent that the paint layer between the metal

delaminates

(from flexing of the joined structure, a distinct possibility) then you

will have an

unprotected crevice for corrosion to start in. On the other hand if you

paint and

assemble dry then you have a crevice but with both surfaces protected by

their paint

layers.

I'm not sure which is better but for my circumstances we have gone with

the latter since

we do not apply paint in our assembly area due to the fumes. Another

justification if I

have to make a case is that Cessna does this also, for what that is

worth.......

As for keeping water out of the structure, for the fuselage seams at

least, we are

looking at using some sort of flexible sealing compound such as the much

maligned proseal

or automotive seam sealer. The auto seam sealer looks like a good bet

since it is

tenaciously sticky, remains flexible and is available off the shelf at

your local

autobody jobber like UAP, no HAZMAT problems. It comes in caulking gun

type tubes that

let you apply as little or as much as you want.

Well, there is my take on it, your mileage may vary :>)

Dave R.

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Charles Skorupa · Post by **Charles Skorupa** » Fri Feb 17, 2012 5:46 pm

Dave,
Good food for thought. I wonder if we are missing the obvious. My boat is
submerged in salt water with all kinds of galvanic action going on due to
stray current (electrical type) at the moorage. Boat owners add zinc plates
to protect the submerged metal surfaces since zinc is more anodic that the
material it is protecting. So even if moisture got in the crevice, the zinc
in the zinc chromate primer would provide substantial level of protection.
Galvanic corrosion, crevice corrosion, oxygen depletion, lions and tigers
and bears, oh my! I'm getting scared to new levels of inactivity. Think
I'll just prime the surfaces, dip the rivets and call it good. If I can do
it wet, great. If not, oh well. I'll build another one in 30 years on my
85th birthday to replace the corroding hulk! Bet I forget about the whole
subject within 10 minutes of the first flight, though. Thanks for the great
suggestions.
- Chuck -

Having a crevice will increase the risk of corrosion, I am not 100%

certain of the

correct approach to avoid this though. If you assemble wet and you have

any relative

movement of the joint to the extent that the paint layer between the metal

delaminates

(from flexing of the joined structure, a distinct possibility) then you

will have an

unprotected crevice for corrosion to start in. On the other hand if you

paint and

assemble dry then you have a crevice but with both surfaces protected by

their paint

layers.

I'm not sure which is better but for my circumstances we have gone with

the latter since

we do not apply paint in our assembly area due to the fumes. Another

justification if I

have to make a case is that Cessna does this also, for what that is

worth.......

As for keeping water out of the structure, for the fuselage seams at

least, we are

looking at using some sort of flexible sealing compound such as the much

maligned proseal

or automotive seam sealer. The auto seam sealer looks like a good bet

since it is

tenaciously sticky, remains flexible and is available off the shelf at

your local

autobody jobber like UAP, no HAZMAT problems. It comes in caulking gun

type tubes that

let you apply as little or as much as you want.

Well, there is my take on it, your mileage may vary :>)

Dave R.

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Bob Patterson · Post by **Bob Patterson** » Fri Feb 17, 2012 5:46 pm

Thanks !! This thread has certainly added to the knowledge base !!

More choices !! :-)

....bobp

--------------------------------------orig.------------------------------------
At 07:15 PM 4/26/00 -0300, you wrote:

Hi Bob

Finally had some time to look into the Imron/Polyurethane question you

raised, I spoke to

Dupont on this today.

The tech rep says that Polyurethane paint by nature is not porous and the

only place they

do not recommend it would be on the bottom of boats because of its

immersion and the

beating it takes can damage it and let moisture through (cracks) but that

is not the

issue here except perhaps for the bottom of floats. The long story of what

he said was

that following their system of materials from start to topcoat (i.e.. metal

prep, Corlar,

primer & Imron) will yield a reliable result for aircraft.

He went on to say that Imron is used on aircraft from small to large with

the exception

of passenger carrying heavies. That exception is intriguing because the

same airframe

could be used for freight and Imron could be used on it. The difference is

that

according to certification standards for commercial passenger aircraft, the

passenger

heavies paint must withstand Skydrol (hydraulic fluid if I am not mistaken)

where the

freighters don't! He also said that they supply the Imron that Fed - Ex

put on their

aircraft.

OK, so much for Dupont's opinion on the subject.

On the RTV you mentioned, it is likely the sort that doesn't contain acetic

acid. Common

RTVs use acetic acid as part of their curing mechanism but it attacks some

materials

including electronics so alternatives have been developed. One company

where I worked

found this out the hard way after sealing some electronics in a housing

using it and all

of a sudden they had failures..... Their choice for a substitute was a Dow

Corning

product, 3145RTV which, like the product you mention is available in tubes

for $8 or 9 a

tube and sold in case lots. My experience with it is that it is a very

good RTV and

makes a fine gasket.......

I haven't made a decision yet but I am still tempted by the automotive seam

sealer since

it sticks like the devil, is readily available, is low cost and is designed

to be painted

over. The last point is important since RTV Silicone typically doesn't

seem to hold

paint well. I am not suggesting to leave a sizable bead of the sealer

showing but where

it does come out of the seam and doesn't get cleaned off perfectly (lacquer

thinner for

the auto product) there will be the question of paint adhesion.

Well, hope this answers a few questions....

Dave R.

Bob Patterson wrote:

Dave,
Sounds like we're both getting the same information. The paint
shops said that they will only use polyurethane paint IF they put a
solid, non-porous layer of epoxy primer UNDER IT.

You are absolutely correct in insisting on using a complete
paint "system" !! Wayne showed us a sample of the results of combining
primer & finishes from different manufacturers (and meant for different
uses) at our last Rebel Builders Meeting !! The finish on his sample
aileron covering just cracked and fell off in chunks, while the sample
done with the Stits (PolyFiber) system thoughout stayed tough and
solid, even when bent, folded, and mutilated !!! This mis-use of
combinations of finishes is what caused Steve Wittman's crash .....

One bit of useful information for the group - there is a good
sealant that should be safe for aircraft use:

It is an RTV Silicone that stays flexible, has good adhesion,
and DOESN'T produce corrosive acids when curing.
This IS NOT 'hardware store' stuff ! It is used to seal the
wire windings in electric motors, electrical connections, and automotive,
truck and trailer bodies, among other things.

It is part # SU 5007 RTV Silicone, from Silicones Unlimited Inc.,
in Marietta,GA (404) 578-1274. It comes in clear, white, gray/aluminum,
black, limestone, and bronze, in caulking gun type tubes. I have a full
data sheet here if anyone wants me to fax a copy. (or call me at
(905)457-5238)

Canadian distributor: Electro-Pulse Enterprises,
Burlington, Ontario L7P 3A7
Tel. (905) 336-7393 Fax: (905) 335-6462

Usually sold in case lots, at about $8-9/tube - might be able to
get a few tubes for folks if there is interest .....

......bobp

--------------------------------orig.------------------------------------------

SNIP!
--
David A. Ricker P. Eng.
DARTEC Engineering Inc.
Fall River, Nova Scotia
Canada
ricker@dbis.ns.ca

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klehman · Post by **klehman** » Fri Feb 17, 2012 5:46 pm

David

Thanks for sharing the paint info.

Unless things have improved lately, I would be wary of auto seam sealer. Any
older vehicles I have worked on always have moisture and rust under those
sealers. And it easily peels off those vehicles of course. Maybe the metal
wasn't cleaned properly before application. Those cars go together pretty
quickly. I haven't found the need for such sealers myself.

Ken

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David A. Ricker · Post by **David A. Ricker** » Fri Feb 17, 2012 5:46 pm

Hi Bob

Finally had some time to look into the Imron/Polyurethane question you raised, I spoke to
Dupont on this today.

The tech rep says that Polyurethane paint by nature is not porous and the only place they
do not recommend it would be on the bottom of boats because of its immersion and the
beating it takes can damage it and let moisture through (cracks) but that is not the
issue here except perhaps for the bottom of floats. The long story of what he said was
that following their system of materials from start to topcoat (i.e.. metal prep, Corlar,
primer & Imron) will yield a reliable result for aircraft.

He went on to say that Imron is used on aircraft from small to large with the exception
of passenger carrying heavies. That exception is intriguing because the same airframe
could be used for freight and Imron could be used on it. The difference is that
according to certification standards for commercial passenger aircraft, the passenger
heavies paint must withstand Skydrol (hydraulic fluid if I am not mistaken) where the
freighters don't! He also said that they supply the Imron that Fed - Ex put on their
aircraft.

OK, so much for Dupont's opinion on the subject.

On the RTV you mentioned, it is likely the sort that doesn't contain acetic acid. Common
RTVs use acetic acid as part of their curing mechanism but it attacks some materials
including electronics so alternatives have been developed. One company where I worked
found this out the hard way after sealing some electronics in a housing using it and all
of a sudden they had failures..... Their choice for a substitute was a Dow Corning
product, 3145RTV which, like the product you mention is available in tubes for $8 or 9 a
tube and sold in case lots. My experience with it is that it is a very good RTV and
makes a fine gasket.......

I haven't made a decision yet but I am still tempted by the automotive seam sealer since
it sticks like the devil, is readily available, is low cost and is designed to be painted
over. The last point is important since RTV Silicone typically doesn't seem to hold
paint well. I am not suggesting to leave a sizable bead of the sealer showing but where
it does come out of the seam and doesn't get cleaned off perfectly (lacquer thinner for
the auto product) there will be the question of paint adhesion.

Well, hope this answers a few questions....

Dave R.

Bob Patterson wrote:

Dave,
Sounds like we're both getting the same information. The paint
shops said that they will only use polyurethane paint IF they put a
solid, non-porous layer of epoxy primer UNDER IT.

You are absolutely correct in insisting on using a complete
paint "system" !! Wayne showed us a sample of the results of combining
primer & finishes from different manufacturers (and meant for different
uses) at our last Rebel Builders Meeting !! The finish on his sample
aileron covering just cracked and fell off in chunks, while the sample
done with the Stits (PolyFiber) system thoughout stayed tough and
solid, even when bent, folded, and mutilated !!! This mis-use of
combinations of finishes is what caused Steve Wittman's crash .....

One bit of useful information for the group - there is a good
sealant that should be safe for aircraft use:

It is an RTV Silicone that stays flexible, has good adhesion,
and DOESN'T produce corrosive acids when curing.
This IS NOT 'hardware store' stuff ! It is used to seal the
wire windings in electric motors, electrical connections, and automotive,
truck and trailer bodies, among other things.

It is part # SU 5007 RTV Silicone, from Silicones Unlimited Inc.,
in Marietta,GA (404) 578-1274. It comes in clear, white, gray/aluminum,
black, limestone, and bronze, in caulking gun type tubes. I have a full
data sheet here if anyone wants me to fax a copy. (or call me at
(905)457-5238)

Canadian distributor: Electro-Pulse Enterprises,
Burlington, Ontario L7P 3A7
Tel. (905) 336-7393 Fax: (905) 335-6462

Usually sold in case lots, at about $8-9/tube - might be able to
get a few tubes for folks if there is interest .....

......bobp

--------------------------------orig.------------------------------------------

SNIP!
--
David A. Ricker P. Eng.
DARTEC Engineering Inc.
Fall River, Nova Scotia
Canada
ricker@dbis.ns.ca

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Bob Patterson · Post by **Bob Patterson** » Fri Feb 17, 2012 5:46 pm

Ken,
Good point ! Neither of our Rebels leaks at the seams - they
were both put together with the PolyFiber Epoxy Primer, WET, in all the
joints. There is NO problem with water leaking in - and FINR has been
outside for most of her 10 years, and she now has about 980 hours of
trouble-free FUN flying on her !!

I haven't heard of ANYONE here having to re-seal their seams !

....bobp

------------------------------orig.----------------------------------------
At 07:19 PM 4/26/00 -0400, you wrote:

David

Thanks for sharing the paint info.

Unless things have improved lately, I would be wary of auto seam sealer. Any
older vehicles I have worked on always have moisture and rust under those
sealers. And it easily peels off those vehicles of course. Maybe the metal
wasn't cleaned properly before application. Those cars go together pretty
quickly. I haven't found the need for such sealers myself.

Ken

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