SEM Self-Etching Primer vs. EZ Coat

[jls32]

I'm just getting started and would like to prime my parts if I can do with a rattle can. So I had settled on SEM Self Etching Primer. When looking at prices on AS, I saw this in the Q&A section:

"Q: Would SEM self etching primer be suitable to use on interior aluminum wing parts by itself for corrosion protection without any top coating?

A: Per supplier, I have spoken to many customers about this application and although it seems to work for them, Self Etching Primer is not intended to be used as a topcoat. My recommendation would be to use our EZ Coat product. It is a direct to metal and aluminum topcoat that has excellent adhesion and is available in 6 colors (Black, Olive Green, Light Green, Gray, Tan, Olive Brown)"

Has anyone used EZ Coat? They say it's "direct to metal" so I assume it's self-etching as well.

Both products say to clean the surface with a cleaner then sand with 320 grit. Is this how everyone is prepping for SEM Self-Etching Primer?

Thanks,
Dan

[wirejock]

Oh yes. This should be fun.
Sorry, welcome. Just kidding. SEM is good stuff if you're settled on rattle can.
Prep is key to painting aluminum. Feel free to read my blog (link below) I get on my soap box about paint prep. I'll save everyone here another diatribe.
On another note...
I manage a Google Group, Colorado RVs
If you would like to join, send me some info (address below) from a G-mail account.
Full Name
Phone
CIty
RV Model

[majuro15]

Not sure about ez coat but I used SEM self etch primer throughout and really like it. Super easy with rattle can. All about proper prepping!

[PaulvS]

I believe that AS is correct and an etch primer alone does not provide any protection from corrosion unless it has zinc chromate in it, which most currently don't.

The etch primer is intended to give a top coat something to stick to and it is porous.

If you want a primer that gives corrosion protection via an impervious barrier then 2-pack epoxy will do this. It obviously doesn't come in a rattle can. Sorry I don't know anything about ez coat.

There are some good historical threads on VAF that explain all of the corrosion protection options and opinions.

[bkervaski]

We used the self-etching for some small parts with a top coat but for the interior we used the 2-part epoxy primer setup with a sealer per SEM's instructions, made for a really durable and easy to maintain flat finish that doesn't chip like paint.

[David Paule]

Here in this part of Colorado, primer is not needed. My 65 year old Cessna, unprimed, has minimal corrosion, and all that came from 6 months parked outside near Philadelphia.

I'm only priming my RV-3B for the benefit of a future buyer.

I used SEM for the bulkheads and small parts. SEM works fine as a barrier but really isn't intended for a rigorously brutal environment. It goes on easily, is reasonably durable, and can be removed if needed with lacquer thinner and some rubbing. I like it a lot.

I use the maroon Scotchbrite, followed by cleaning with lacquer thinner or denatured alcohol, for prep. Sanding is not required.

I've used the water-based Stewart Systems Ekopoxy for a few parts where I wanted something more durable. It sprays easily and is a nice finish. I used it for the baggage area and seat, to get more light in there.

I'm up in Boulder if you'd like to see for yourself.

Dave

[9GT]

Many years ago when building my RV-10, I did a coupon scratch test using various rattle primers. The SEM self etch primer won hands down.

[jls32]

I contacted SEM and this is what they said:

"Due to the heavier solids content, the EZCOAT will be better for corrosion protection. Although there is no acid in the EZCOAT, it will adhere to clean, sanded aluminum as well as SELF ETCH PRIMER. It also handles UV better than the primer. Etch primers do not have a high solids content so do not provide a significant film build and will not handle abrasion as well as EZCOAT."

EZCOAT is a bit more expensive than the etch primer.

[MIKE JG]

The more I read these primer threads, the less I understand.....

So you're telling me the self etching primer has no corrosion proofing value??

So literally if I'm using the self etch primer from SEM (which I am) I'm wasting my time??

[BobTurner]

Originally Posted by MIKE JG

The more I read these primer threads, the less I understand.....

So you're telling me the self etching primer has no corrosion proofing value??

So literally if I'm using the self etch primer from SEM (which I am) I'm wasting my time??

It?s a question of degree. In some sense all paints are porous. Primers more so, as the tiny pores give the top coat a place to grab. But depending on where you live, it might go like this (I?m just making these numbers up-it really depends on environment): nothing, lifetime=10 years; primer only, lifetime=50 years; primer plus sealing top coat, lifetime=200 years. You decide.