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02-20-2017, 09:17 PM
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Join Date: May 2013
Location: Mount Vernon, Wa
Posts: 643
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If you're going to go to the expense and hassle of alodining, then make sure you follow that up with a good epoxy primer, or at least a zinc chromate out of a rattle can. The 2-part epoxy primers used on military aircraft is some really tough stuff and easy to spray. But, to get get acceptable coverage, you will be adding some weight. I know, because I sprayed a lot of it back in my old Navy days.
That being said, if you haven't read Scott McDaniels' article in "27 Years of the RVator", you should.
I've been using SEM self-etching primer from a rattle can for everything. I use halogen lamps to keep the surface temp up for curing over a 24 hour period before trying to rivet it. After several weeks at typical garage shelf temperatures, its pretty durable. But, you've gotta put it on in 2 to 3 thin coats, and the surface has got to be CLEAN!
I've just bought some Variprime 615S with 616 reducer. I'm going to try Sam Bovington's wipe-on primer technique because I think it will be even easier, and perhaps even save even an ounce or two more over the rattle can.
I looked at Sam's aircraft, and I can tell you the primer looks pretty hardy to me.
__________________
Ken W.
Mount Vernon, WA
2020 VAF Supporter
Last edited by N804RV : 02-20-2017 at 11:25 PM.
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02-21-2017, 06:49 AM
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Join Date: Jan 2005
Location: SC
Posts: 12,887
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I did both Alodine and then painted over it with SEM rattle cans. Nine years in the South Eastern US and not indication of corrosion.
Here is what I wrote on my website about it.
One other thing, to make the spray can paint flow better, I would shake the cans, place the can(s) in front of my small space heater, and shake them again before each use. Then after a pass or two I would dab the nozzle with a paper towel to remove any paint that collected there and keep it from "spitting".
At the end of each work session, I would lightly scrub the parts with a scotch bright pad, clean them with Alumiprep, rinse, alodine them, rinse, and set them out to dry. The next morning I would get up 15 minutes early and go into the basement and spray them with the SEM primer, shower, eat, and leave for work. When I came home, the parts were ready to assemble.
If you find that the primer would come off in big (or small) flakes, the aluminum was probably still damp when you sprayed it.
__________________
Bill R.
RV-9 (Yes, it's a dragon tail)
O-360 w/ dual P-mags
Build the plane you want, not the plane others want you to build!
SC86 - Easley, SC
www.repucci.com/bill/baf.html
Last edited by N941WR : 02-21-2017 at 06:52 AM.
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02-21-2017, 07:38 AM
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Join Date: May 2006
Location: Pocahontas MS
Posts: 3,884
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I can't see why you'd prime internal parts after alodining (see posts #5 & 6).
Also, I'm no expert on paint, but the references I've seen say that if you alodine, you shouldn't use a self etching primer over it. Logic was, the etch step was done by the acid etch step prior to alodine, and the alodine 'converts' the surface. A self etching primer is trying to remove corrosion that was already removed by the etch/alodine process, so at best it's a waste & at worst, it destroys the alodine process. Not saying the paint won't stick, but corrosion protection is no better (possibly worse), and it's extra weight and extra work (Yuck).
Charlie
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02-21-2017, 08:50 AM
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Join Date: May 2013
Location: Mount Vernon, Wa
Posts: 643
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Quote:
Originally Posted by rv7charlie
I can't see why you'd prime internal parts after alodining (see posts #5 & 6).
Also, I'm no expert on paint, but the references I've seen say that if you alodine, you shouldn't use a self etching primer over it. Logic was, the etch step was done by the acid etch step prior to alodine, and the alodine 'converts' the surface. A self etching primer is trying to remove corrosion that was already removed by the etch/alodine process, so at best it's a waste & at worst, it destroys the alodine process. Not saying the paint won't stick, but corrosion protection is no better (possibly worse), and it's extra weight and extra work (Yuck).
Charlie
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Alodine is a chemical conversion coating. It is not durable. It is meant to improve adhesion of the primer. This is why you don't leave bare alodine, and why using a self-etching primer over it is redundant.
__________________
Ken W.
Mount Vernon, WA
2020 VAF Supporter
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