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09-07-2012, 08:30 AM
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Join Date: Aug 2012
Location: Greenville, SC
Posts: 50
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Sanding (Scuffing) before priming (Aluminum)
Hi,
I see a lot of posts where people sand insides before priming. I understand why sanding is needed, but I'm confused about sanding Alclad. Don't you remove it completely and reduce corrosion protection?
I'm just about to start on the empennage... What did I get myself into...
Thanks,
Yuri
__________________
Yuri
DA40
RV-10 - build in progress
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09-07-2012, 08:37 AM
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Join Date: Aug 2009
Location: Winnipeg, Canada
Posts: 214
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Hi Yuri and welcome to VAF!
I've just started my -9A so I can understand you have lots of questions. Regarding sanding before priming. We're not sanding off the Alclad but are just scuffing it up so the primer can hold better. Some will argue that scuffing is not necessary if you're using a self-etch primer but that's up to you to decide.
Cheers,
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09-07-2012, 09:13 AM
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Join Date: Oct 2007
Location: In New Braunfels, ist das Leben schön!
Posts: 871
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Hi Yuri,
If you ask 5 people about priming, you'll get 10 opinions. There has been so much written on the subject on this forum that there is an entire section dedicated to the topic.
Read what you can about it on VAF but be sure and carefully read what Van says about it in chapter 5 of the build manual. One of the products Van recommends for priming is Sherwin Williams G60P2 Wash Primer. I did an informal test of it over scuffed, unscuffed, and primed with NAPA 7220 aluminum and couldn't tell any difference in the toughness or adhesion on the three sections.

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Larry New
RV-7A - Built, flying 900+ hrs
RV-10 - Built, flying 2.9 hrs
??? - RV-12, Subsonex
48 States in 7 Days!
VAF Paid - Annual Autodraft
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09-07-2012, 12:54 PM
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Join Date: Jan 2005
Posts: 3,646
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Quote:
Originally Posted by localizer
Hi,
I see a lot of posts where people sand insides before priming. I understand why sanding is needed, but I'm confused about sanding Alclad. Don't you remove it completely and reduce corrosion protection?
I'm just about to start on the empennage... What did I get myself into...
Thanks,
Yuri
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Don't sand! Just scuff the gloss off with a maroon scotchbrite pad.
__________________
Steve M.
Ellensburg WA
RV-9 Flying, 0-320, Catto
Donation reminder: Jan. 2021
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09-07-2012, 02:50 PM
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Join Date: Aug 2012
Location: Greenville, SC
Posts: 50
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Thank you all for correcting me (I used wrong terminology - sanding instead of scuffing).
I will proceed with various ways on a sample sheet and then choose my way. :-)
Yuri
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Yuri
DA40
RV-10 - build in progress
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09-07-2012, 06:54 PM
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Join Date: Dec 2006
Location: Paso Robles, CA
Posts: 1,177
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Better than Sandpaper for getting it clean.
I use Maroon scotchbrite on bare aluminum with detwegent that does not leave any residue after clear water rinse. Then I blow it off with very clean compressed air.
Do not touch it with your bare hands until it is alodined or applying acid etching primer.
I went with the Azco Nobel acid etch Zinc Chromate Primer.
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09-07-2012, 10:20 PM
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Join Date: Jan 2005
Location: 57AZ - NW Tucson area
Posts: 10,011
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Quote:
Originally Posted by GAHco
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I went with the Azco Nobel acid etch Zinc Chromate Primer.
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Which one is that? Looking at the MSDS sheets, I believe the Spruce one ( 463-12-8 + C116) sold is not acid etch.
It's also Strontium Chromate. Is there another one you are using?
Alumiprep first is a good idea with the Spruce product...
__________________
Gil Alexander
EAA Technical Counselor, Airframe Mechanic
Half completed RV-10 QB purchased
RV-6A N61GX - finally flying
Grumman Tiger N12GA - flying
La Cholla Airpark (57AZ) Tucson AZ
Last edited by az_gila : 09-07-2012 at 10:22 PM.
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09-08-2012, 04:07 PM
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Join Date: Dec 2006
Location: Paso Robles, CA
Posts: 1,177
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I went in my garage and found the #
They call it Zinc Chromate Wash Primer.
Product # G9072
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09-08-2012, 10:35 PM
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Join Date: Jan 2005
Location: 57AZ - NW Tucson area
Posts: 10,011
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Quote:
Originally Posted by GAHco
They call it Zinc Chromate Wash Primer.
Product # G9072
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Ahh... it's an AwlGrip product.
I didn't realize Akzo Nobel bought them out...
The application instructions still specify an acid etch first though...
Surface Preparation
Steel--solvent clean, grind.
Aluminum--deoxidize with ALUMIPREP? 33.
http://pinmar.com/awlgrip/tds/76.html
__________________
Gil Alexander
EAA Technical Counselor, Airframe Mechanic
Half completed RV-10 QB purchased
RV-6A N61GX - finally flying
Grumman Tiger N12GA - flying
La Cholla Airpark (57AZ) Tucson AZ
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