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Primer testing and selection

This is not about "should I Prime or not". More about selecting a Primer.
I wanted to use a "shake can" primer (convenient), so I tested 8 different ones.

I sprayed on a clean piece of AL skin (no special treatment or scrubbing, just remove the blue vinyl), let it sit for 3 minutes and did a touch test, so see if it was quick to dry.

After ~10 minutes I did the "fingernail scratch" test, 24 hours later I repeated the scratch test.
The winners are the ones that dried quickly and resisted the fingernail scratch test completely, no scratch.

  • The clear winner is SEM PRIMER SELF ETCHING PRIMER (~$20 per can)
  • Followed [very] closely by Rust-OLEUM Professional Aluminum Primer (lowest cost)
  • Then Majic Fast DRY SELF-ETCHING Primer

All the others (5) did not get close. The winners dried very quickly and resisted the scratch test, no matter how hard I tried!

If someone wants the image of all 8 test candidates, please email me, I will send back.

I hope this helps.
 
  • The clear winner is SEM PRIMER SELF ETCHING PRIMER (~$20 per can)
  • Followed [very] closely by Rust-OLEUM Professional Aluminum Primer (lowest cost)
  • Then Majic Fast DRY SELF-ETCHING Primer

Is this the Rust-Oleum product you tested??

71Np%2BhftijL._SL1500_.jpg
 
Gorilla tape test

Now rub a piece of Gorilla tape on each. Leave it over night and rip it off.
The Aluminum Oxide is still there and primer could still flake off later.
Surface prep matters.
 
Looks very close, Maybe the can I have is newer.

It was as good as the winner, but since it did not say "Self Etching" I selected the SEM, just to be safe.

How can I easily insert a picture in the Post? (vs a link)
 
Of course surface pre is important, fully agree.
My intention was to select a primer, not to protect a surface.
I assume that my winner will be even better on a properly prepped surface.

BTW, the aluminum sheets I used for the testing was ~16 years old practice sheet that came with a Box example and a wing element that Vans still sells. The vinyl was still on, I bet the surface had AL oxide.

OTOH, I also believe that any priming, even w/o proper prepping is better than no priming at all. On my build, (all new clean surfaces) I only prime the contact surfaces (both sides), I do no surface prepping.

A
 
SEM

Of course surface pre is important, fully agree.
My intention was to select a primer, not to protect a surface.
I assume that my winner will be even better on a properly prepped surface.

BTW, the aluminum sheets I used for the testing was ~16 years old practice sheet that came with a Box example and a wing element that Vans still sells. The vinyl was still on, I bet the surface had AL oxide.

OTOH, I also believe that any priming, even w/o proper prepping is better than no priming at all. On my build, (all new clean surfaces) I only prime the contact surfaces (both sides), I do no surface prepping.

A

My apologies Armando. My grandson's name.
I should not have jumped in with a comment about surface prep. You are correct. SEM is a superior product. NAPA 7220 is also good.
Aluminium prep is a subject dear to my heart. Build on.
 
I use SEM products also, but I have switched from self etching primer to their EZ-Coat system. In conversations with their tech support team they stated that the primer needs a top coat, by itself it does not protect against corrosion. The EZ-Coat however does. Bit longer drying time and it goes on a bit thicker, but still a rattle can system.

I follow their directions, spray down with SEM surface prep, then about 2 coats of EZ-Coat.
 
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