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Need Help Painting Aluminum

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Robert Schieck

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Jan 28, 2002, 2:24:01 PM1/28/02
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Hi:

I must be doing something wrong after 24 hours of drying I can scrape
the primer off with my thumb nail.

I am trying to paint aluminum. I use the following steps:

1) clean with acetone
2) remove outer layer of oxide with scotch brite pad
3) clean with acetone
4) place in Alumiprep 33 for 3 - 5 minutes
5) rinse with water
6) place in alodine 1201 (the gold stuff)
7) rinse with water
8) dry
9) paint (within 8 hours) with zinc Chromate primer (Tempo 5605C).
10) let dry.

It has been 24 hours since the zinc chromate primer was put on and I can
scrape it off with my thumb nail.

Any suggestions on how to get it to stick better ?

thanks

Rob

Kyle Boatright

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Jan 28, 2002, 6:05:10 PM1/28/02
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Rob,

My experience is that Zinc Chromate from the Tempo spray cans is extremely slow
to harden. If you'll leave it alone for a few weeks before trying the
thumbnail test, you'll get much better results.

KB

Jim Vandervort

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Jan 28, 2002, 8:29:11 PM1/28/02
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There has never been any paint in a spray can that was worth a rats ass.

assa9

Kyle Boatright <kboat...@aol.comnobs> wrote in message
news:20020128180510...@mb-dd.aol.com...

Jim

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Jan 28, 2002, 1:01:23 PM1/28/02
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If the paint peels off you are appling a too heavy coat. The coat should be
transparent. Full coverage but just enough to cover and no more. Again you
should easily see through to the painted surface.
Just an opinion mindya
Jim

Robert Schieck wrote in message <3C55A551...@mers.com>...

Rip

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Jan 28, 2002, 10:26:59 PM1/28/02
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Aside from the fact that Temco chromate takes a LONG time to dry:
1) skip the acetone. Wash the parts with Dawn dishwashing detergent,
rinse well, and go straight to the Alumiprep, diluted 3:1 with water.
Apply it with a maroon scotchbrite pad until you get a continuous sheet
of water on the part (no beading). Rinse well, and apply the alodine
with a mop, rag, or foam brush. Keep the part wet for 2-3 minutes. DON'T
soak the part in either the alumiprep or alodine. Too much alumiprep
leaves a "smut" film on the part, and too much exposure to alodine makes
a thick poorly adhered chromate film. Rinse well, and let dry
thoroughly. A new alodine (chromate) film is very soft, and takes a good
24 hours to harden. Now paint, preferably with a good chromate epoxy if
your part won't see sunlight, or Tempco if you've got to. Be patient. It
will dry.

Richard Lamb

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Jan 28, 2002, 11:13:19 PM1/28/02
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That was a keeper, Rip.
Thanks

c hinds

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Jan 28, 2002, 11:32:11 PM1/28/02
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kboat...@aol.comnobs (Kyle Boatright) wrote in message news:<20020128180510...@mb-dd.aol.com>...

Rob,
I had a similar experience and was guided by an old pro who had
designed and built many metal aircraft. His suggestion was to clean,
alumiprep, rinse well and then coat with a two part etch primer
followed by zinc chromate.
I did just this and the results are great. The etch primer gives the
much needed tooth for the zinc chromate and provides a molecular bond
with the aluminum. Whatever you top it with will stay put.
Good Luck,
CH

Scrappman

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Jan 29, 2002, 10:40:03 PM1/29/02
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Best to clean it,( soap and water),,, hit it with phosphoric acid,, seal
with cromic acid, coat it with a light coat of TWO PART zinc cromate,, don't
let it dry for two many days before top-coating. Or you'll have to re-prime
it. Most two part zink primers shell out after a few days, making break'n
the surface pretty tough.
Iff'n ya don't want to go thru all that, go to your nearest boat
dealer,,,, get some undercoats,( they all have their line of product) and
top coats,, follow their steps to a T. Valspar has a great alum boat
finishing system, and their under coats are latex,, weight is a little
higher than aircraft finishes. Holds up on floats surprisingly well.
Scrappman

Robert Schieck

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Jan 30, 2002, 1:49:56 PM1/30/02
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To every one who answered, many thanks.

My problems are quite simple, no patience, no patience and too much
primer....

Many thanks

Rob from Ontario Canada

Bobby Hester

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Jan 31, 2002, 8:13:04 PM1/31/02
to Kyle Boatright
Jim Vandervort wrote:

I am priming my RV7A wing ribs and it is sticking great.

1. scuff with scotch brite
2. clean with a paint prep
3. prime with NAPA part#7220 self etching primer (grey) out of a spray can $5 a
can

Wait 30 min. dry to the touch wait an hour and do what ever you want to it.

I had the tip on one can mess up and the primer was pouring out, wiped up the
puddles waited about 30 mins.and was going to lightly scuff the area to smooth
and reprime. Wrong I had to scuff very hard to smooth it out, so I do not think
it would scratch off.

--
Surfing the Web from Hopkinsville, KY
Visit my web site at: http://www.geocities.com/hester-hoptown/RVSite/
Starting RV7A wings :-)


Charlie Brown

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Feb 1, 2002, 12:05:55 AM2/1/02
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Putting zinc chromate over two part etch primer is a waste of
time, money, creates dead weight and probably weakens the bond
between the finish and the primer. Used properly, zinc chromate
(.0005 thick) forms a chemical bond to the aluminum surface as
does the two part etch primer. There is no reason to use both.

Ray

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