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Sanding (Scuffing) before priming (Aluminum)

L

localizer

Active Member
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
 
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,
 
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.

IMG_2238.JPG
 
localizer said:
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
Click to expand...
Don't sand! Just scuff the gloss off with a maroon scotchbrite pad.
 
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
 
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.
 
GAHco said:
....
I went with the Azco Nobel acid etch Zinc Chromate Primer.
Click to expand...

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...
 
Last edited:
I went in my garage and found the #

They call it Zinc Chromate Wash Primer.

Product # G9072
 
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