The Murphy Builders Site

What are the thoughts of you good folks on preparation for painting? My
FBO says there are steps:

1) Scotchbrite with an acid etch, wash off thoroughly
2) Alodine, wash off
3) Primer wash
4) Epoxy primer

At least steps 1-3 have to be completed without undue delay.

I wonder if the acid etch will go for the steel mandrels on the Avex
rivets? I'm thinking about filling the rivets with a drop of automotive
filler (Dupont 30S) to close them off anyway, but that'll be a fair bit
of work. I'm concerned the steel will rust and stain the exterior
paint.

Al Hepburn



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Hi Alan,

Used the scotchbrite with acid etch and alodine, then a self etching primer,
Dura-prime (I think) on my CH 701 with avex rivets. I painted it in '91. It
was sold in '00 and the Dupont base coat clear coat looked like the day I
shot it, perfect. No sign of any problems with the rivets Zenair supplied. I
have not heard the new owner having any problems and we touch base once in a
while.

Hope this helps,
Don B.

From: Alan Hepburn <ahepburn@renc.igs.net>
Reply-To: murphy-rebel@dcsol.com
Date: Thu, 22 Apr 2004 23:02:02 -0400
To: murphy-rebel@dcsol.com
Subject: Paint Prep.

What are the thoughts of you good folks on preparation for painting? My
FBO says there are steps:

1) Scotchbrite with an acid etch, wash off thoroughly
2) Alodine, wash off
3) Primer wash
4) Epoxy primer

At least steps 1-3 have to be completed without undue delay.

I wonder if the acid etch will go for the steel mandrels on the Avex
rivets? I'm thinking about filling the rivets with a drop of automotive
filler (Dupont 30S) to close them off anyway, but that'll be a fair bit
of work. I'm concerned the steel will rust and stain the exterior
paint.

Al Hepburn



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I'm prepping my rebel for seaplane duty. Clean with MEK or acetone,
alumiprep and alodine (while wet), self-etching primer, epoxy primer (I used mil
spec), top coat. Steel rivets will corrode, both on the inside where mandrel
pulled out and on the back side. Rivets come with slight manufacturing oil which
repels coatings/primer if left uncleaned. I fill rivets with epoxy primer
using a syringe (mil spec epoxy primer has corrosion inhibitors). Work best if
mating surfaces are epoxy primed and rivets are cleaned and dipped in epoxy
primer before riveting (epoxy primer won't completely get between mated surfaces
after riveting).

Tony



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There are lots of comments in the archives that seem to say that mandrel
rusting is simply not a problem even with no extra attention. I believe
the same is true for the larger 5/32 rivets on Zeniths.

I also concluded that unlike the 2000 series Cessna aluminum that your
FBO is probably used to, there is little point in exposing myself or the
environment to alodine chemicals for 6061 on a Rebel.

So I degreased with MEK/acetone, scotchbrited with alumniprep, then
applied epoxy primer to my fuselage several years ago. Adhesion has been
very good. The paint manufacturers say that I should re-prime with their
own primer before painting so if you use epoxy primer make sure it
matches whatever topcoat you are going to use. Some also have a time
limit for recoating.

Is "primer wash" a self etching primer? If so I thought that was the
only primer normally used?

Ken

Alan Hepburn wrote:

What are the thoughts of you good folks on preparation for painting? My
FBO says there are steps:

1) Scotchbrite with an acid etch, wash off thoroughly
2) Alodine, wash off
3) Primer wash
4) Epoxy primer

At least steps 1-3 have to be completed without undue delay.

I wonder if the acid etch will go for the steel mandrels on the Avex
rivets? I'm thinking about filling the rivets with a drop of automotive
filler (Dupont 30S) to close them off anyway, but that'll be a fair bit
of work. I'm concerned the steel will rust and stain the exterior
paint.

Al Hepburn

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Hi Al !

Your FBO has given you the standard process...
The Alodine is a corrosion prevention layer - in MHO it is not strictly
necessary. Some shops go straight to primer after etch - have had 2 Rebels
done that way. Etch & alodine are toxic, and require proper haz-mat
disposal techniques - and be sure to flush the etch VERY thoroughly.
It will keep on etching in cracks & joints ! (This is why I'm not
a big fan of 'self-etching' primers !)

You will find that prep & paint are VERY controversial topics,
and everyone has their own preferences !! ;-) Take all the advice,
then make your own choice - as i know you will. ;-)

One VERY important consideration is to use ONE "paint system"
throughout - that is, ALL from one manufacturer, in a combination that
was designed to work together, from wash coat (if required), to primer,
to finish paint. You may remember cars that had peeling paint & clear
coat a few years back - this was caused by using primer from one company,
paint from another, and clear coat from the next lowest bidder ! :-(

I have had good luck with R-M Epoxy Enamel (brand name UNA),
which is a 2 part paint that is the middle grade in R-M's product lineup.
R-M is a professional-level automotive paint, and only available through
auto wholesalers or body shops. It is quite glossy, retains its shine,
and flexible enough for years of aircraft use without adding flex agents.

As for the rivets - save your energy ! Filling them will take lots
of effort, add weight, and possibly end up with the filler cracking & falling
out later. If you paint with a High Volume/Low Pressure system, there will
be plenty of paint to flow into the rivet heads. The OLD spray systems did
often blow so hard the paint didn't get into the heads, but HVLP solves this.

The original Rebel prototype has spent most of its 14 years outside,
and, last I saw of it, there might have been 2 or 3 rivets that you could see
a bit of rust inside, if you peered into them - NO staining of the rest of
the paint. I believe there is a chemical (phosporous ??) in the steel
rivet mandrels that prevents/delays corrosion over the area of the shear.

My latest Rebel is in the shop now for paint - I've chosen to
have John Goris at Purple Hill Air, near London do the prep and paint.
John is an AME, and has a complete paint shop setup on his own airfield,
so prices are reasonable, and the work I've seen is excellent.

I don't have the facilities for paint, don't care to risk what
little health I have left, and certainly don't have the skills to risk
messing up my airplane, sooooooo .... John gets the job !

Just my choices & reasons - YMMD !! ;-) :-)

......bobp

----------------------------orig.-------------------
On Thursday 22 April 2004 11:02 pm, you wrote:

What are the thoughts of you good folks on preparation for painting? My
FBO says there are steps:

1) Scotchbrite with an acid etch, wash off thoroughly
2) Alodine, wash off
3) Primer wash
4) Epoxy primer

At least steps 1-3 have to be completed without undue delay.

I wonder if the acid etch will go for the steel mandrels on the Avex
rivets? I'm thinking about filling the rivets with a drop of automotive
filler (Dupont 30S) to close them off anyway, but that'll be a fair bit
of work. I'm concerned the steel will rust and stain the exterior
paint.

Al Hepburn



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Paint hasn't fallen off my airplane yet (9 years this week!), except where
someone had picked up a gear cover with bare hands and put back on the rack
we where painting on. Mine was rubbed down all over with medium scotchbrite,
cleaned off with cleaner/wax remover ...that any car gets cleaned off with
prior to paint. Then shot with self etching epoxy primer and immediately
followed up with colour coats. All PPG two part epoxy urethane
product...start to finish. All colours had to be on top of the primer within
72 hours .....or you have to sand between coats (and that would be no fun
with all those bumps sticking up on the skins!). No etching, and especially
no alodine! You don't need a coversion coating on 6061. It's not 2024-T3
alcad that you just removed the protective layer on by scrubbing.....our
6061-T6 is "bare" (top to bottom!)

If you don't have a fresh air hood....don't do it yourself (at least have
someone around to drag your carcass out of the booth...just kidding!!)!

Wayne

----- Original Message -----
From: "David Ricker" <ricker@inherentsys.ca>
To: <murphy-rebel@dcsol.com>
Sent: Friday, April 23, 2004 7:01 PM
Subject: Re: Paint Prep.

Hi Bob

Well, as you say there are many opinions on this and I would like to toss

in my

two cents worth for the sake of completeness ;^)

Bob Patterson wrote:

Hi Al !

Your FBO has given you the standard process...
The Alodine is a corrosion prevention layer - in MHO it is not strictly
necessary. Some shops go straight to primer after etch - have had 2

Rebels

done that way. Etch & alodine are toxic, and require proper haz-mat
disposal techniques - and be sure to flush the etch VERY thoroughly.
It will keep on etching in cracks & joints ! (This is why I'm not
a big fan of 'self-etching' primers !)

I'm not so sure about the etching continuing for ever. From my first year
chemistry I recall the need for there to be an adequate supply of all the
reactants to be present for a reaction to continue, I expect that there is

only

enough of the etching chemical in either the etch solution or the primer

to treat

a very thin layer of the surface of the material before it is used up and

the

chemical reaction stops.

If it went on continuously I think there would be aluminum structures

falling

apart everywhere. In either case the wet film is very thin so there is

not much

volume to carry the reactive chemical so after treatment and a good wash

off for

the etch solution or curing of the epoxy primer I would not worry about

the

reaction continuing. In any case we aren't and we are using Dupont Corlar

which

is an etching epoxy primer with chromate and recommended for the

application by

the Dupont tech staff.

You will find that prep & paint are VERY controversial topics,
and everyone has their own preferences !! ;-) Take all the advice,
then make your own choice - as i know you will. ;-)

One VERY important consideration is to use ONE "paint system"
throughout - that is, ALL from one manufacturer, in a combination that
was designed to work together, from wash coat (if required), to primer,
to finish paint. SNIP!

Good advice here!

Cheers,

Dave R
www.elite583.cjb.net


--
David A. Ricker
Fall River, Nova Scotia
Canada

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Hi Bob

Well, as you say there are many opinions on this and I would like to toss in my
two cents worth for the sake of completeness ;^)

Bob Patterson wrote:

Hi Al !

Your FBO has given you the standard process...
The Alodine is a corrosion prevention layer - in MHO it is not strictly
necessary. Some shops go straight to primer after etch - have had 2 Rebels
done that way. Etch & alodine are toxic, and require proper haz-mat
disposal techniques - and be sure to flush the etch VERY thoroughly.
It will keep on etching in cracks & joints ! (This is why I'm not
a big fan of 'self-etching' primers !)

I'm not so sure about the etching continuing for ever. From my first year
chemistry I recall the need for there to be an adequate supply of all the
reactants to be present for a reaction to continue, I expect that there is only
enough of the etching chemical in either the etch solution or the primer to treat
a very thin layer of the surface of the material before it is used up and the
chemical reaction stops.

If it went on continuously I think there would be aluminum structures falling
apart everywhere. In either case the wet film is very thin so there is not much
volume to carry the reactive chemical so after treatment and a good wash off for
the etch solution or curing of the epoxy primer I would not worry about the
reaction continuing. In any case we aren't and we are using Dupont Corlar which
is an etching epoxy primer with chromate and recommended for the application by
the Dupont tech staff.

You will find that prep & paint are VERY controversial topics,
and everyone has their own preferences !! ;-) Take all the advice,
then make your own choice - as i know you will. ;-)

One VERY important consideration is to use ONE "paint system"
throughout - that is, ALL from one manufacturer, in a combination that
was designed to work together, from wash coat (if required), to primer,
to finish paint. SNIP!

Good advice here!

Cheers,

Dave R
www.elite583.cjb.net


--
David A. Ricker
Fall River, Nova Scotia
Canada





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Thanks Wayne and all others who responded . I was pretty sure I'd get a
variety of opinions , and will consider all of them.

Regards, Al



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