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Rattle Can Comparison

mlwynn

Well Known Member
Hi all,

I was reading through the rattle can discussion and thought a head to head comparison might be useful. I am acquiring as many variations as I can easily find. I have self-etching primers from Duplicolor, Marhyde, SEM, and rustoleum so far.

The question I had is how to set up the test. I was going to start with standard alclad. I thought I would do a strip with just careful cleaning. A second one scubbed with red scotchbrite. Maybe a third with scotchbrite and an acid etcher. When I built my RV8, I went totally nuts on this. I scuffed with scotchbrite in an alumiprep bath (phosphoric acid). I then conversion coated with a product whose name escapes me. Works like Alodine but uses a potassium permanganate solution that is totally non-toxic. Followed that with Azko-Nobel two part epoxy primer. The end result is hard as nails and impervious to everything--but probably cost me a year in building and who knows how many brain cells.

I'm starting a -10 and plan to prime all surfaces where metal touches but not the skins. I think a good rattle can is probably quite adequate. I am waiting for the empennage kit to arrive so I have time to experiment. Any thoughts as to additional tests?

Regards,
Michael Wynn
RV8 flying
RV10 Starting
 
Tests

It was only a week or so ago that there was a similar post on VAF. The OP tested various primers, using non-alclad so as to eliminate the protective coating from the comparison, and then subjected the test pieces to a salt spray test. After the test there was a marked difference in the protection offered by the various brands and I think the Tempo was the winner. Here is the link to that post:
https://vansairforce.net/community/showpost.php?p=1518353&postcount=69
 
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I didn't like duplicolor. I tried a can or two. I think SEM is pretty good for rattle can primer. You can get it in green and grey. It's not cheap though. I use it some times when I just have a part or two that I'm trying to finish up and I don't feel like mixing a batch of epoxy primer. The epoxy primer is more durable though.
 
Aircraft Spruce sells various primers from PTI in rattle cans. While there is Zinc Chromate available, I'd stay away from it and test their Zinc Oxide or Phosphate primer.

I used it on my wings and was fairly happy with the results. Although I didn't do a corrosion test like you are proposing.
 
My own impression of the Zinc Phosphate primer is that it did not spray nearly as well as the SEM primer.

Dave
 
NAPA 7220

Add NAPA 7220 to the test.
Try combining steps.
Scuff and clean in one step using maroon scotchbrite and Bon Ami cleanser.
 
Primer comparison

The article on salt fogging was interesting. Good job on the test. No question that a two part epoxy primer is superior. It is also requires a lot more prep.

Anyway, I will see how this comes out.

Regards,

Michael Wynn
Livermore, CA
 
I had done that salt fog test mentioned above using non-alclad material. If I did it again, I would do it with alclad, so your test will be interesting. The reason I didn't use alclad, is because alcad is already a pretty good barrier against corrosion. Using non-alclad let me really see how the different primers fared relative to each other with regards to corrosion.

In doing any test, you definitely need make clear goals for the test. Are you looking simply at durability? Corrosion? As I mentioned in my article about the test, so many like to discuss the durability or how well a particular primer sprays. For me, corrosion resistance was paramount. I had found that even though Tempo Zinc Phosphate doesn't spray real great, it was the only one of the tested primers (Tempo ZP, SEM, Dupli-Color, EkoPrime) that fully prevented corrosion under the specific conditions of my test.
 
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