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PPG Epoxy primer not very durable?

rvator51

rvator51

Well Known Member
I painted the interior skins/bulkheads on my first RV with Dupont Veriprime, but switched over to PPG DP50LF Epoxy based primer for the RV-4 I am building based on others recommendations.

After using the PPG epoxy primer for a while, I find that it is a lot more easily scratched and comes off more easily with paint thinner/solvent. I have to be a lot more careful with it than the Veriprime. Supposely it seals the aluminum against corrosion a lot better than Veriprime, but it doesnt seem to stand up as well. I was going to paint the interior of my cockpit with it and just leave it. Now having second thoughts.
Am I doing something wrong or is there a hardener you can add to it to make it more durable?
 
Preparation

Tom ... what surface preparation are you doing?

The PPG spec. sheet calls for aluminum to be cleaned and sanded, or acid etched and alodined.

With no acid etch/alodine, the required thickness is double that of etched/alodined aluminum.

It seems like the manufacturer does not think cleaning is good enough, and requires sanding... way too much for us. If you don't do this, then acid etch/alodine is needed.

It sure sounds like your stuff is not sticking.....

I presume you are using the DP402LF as the hardener....

Spec. sheet is here....

http://www.ppg.com/refinishftpsite/...r.pdf#search="PPG DP50LF Epoxy based primer "

I've used the DP40 in the past (before it got the LF for Lead Free variation) and it gets hard, and sticks well to etched surfaces - an RV-6A exterior in this case.... and it flew for a year in partial primer...

gil in Tucson
 
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The DP primer does not stand up well to solvents, but should stay put if you prep properly. Also, being an epoxy, it gets harder over an extended period.
 
Maybe I'm doing something wrong, but my experience was that just about anything would disolve Variprime. MEK, acetone, alcohol, not gasoline thank heaven. I bought a gallon of it because I thought, being self-etching that it would save some time, and some weight. After I saw how easily it came off, I went back to AKZO (which I can't get off with sandpaper). Is your experience different?
 
Yes

tomcostanza said:
Maybe I'm doing something wrong, but my experience was that just about anything would disolve Variprime. MEK, acetone, alcohol, not gasoline thank heaven. I bought a gallon of it because I thought, being self-etching that it would save some time, and some weight. After I saw how easily it came off, I went back to AKZO (which I can't get off with sandpaper). Is your experience different?
Click to expand...

Don't know about others....

But this is exactly what I found... VariPrime is not an epoxy....
Acetone removes it - don't use a Sharpie on it.... :)

gil in Tucson
 
I found the PPG DP50 (before lead free) to be extremely durable. So much so, I decided to use it for most of the final finish in my plane interior. This was in addition to every square inch of aluminum and steel throughout the rest of the plane.

How it compares with others? Who knows. But what I found out after time was that primer (especially DP50) does not seal 100%. It will need a top coat if you want a truly sealed surface. I have the rust bloom in my DP50 coated steel and subsequent testimony from PPG DP50 knowledgable people to prove the fact.

Might be OK for aluminum, but definitely not adequate alone for steel.
 
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KTM520guy said:
One of the things that doesn't get Vari-Prime off is paint stripper.
Click to expand...

????
It doesn't come off in wrinkled layers like top coats, but it does turn it into a sludge.
MEK takes VariPrime off quite nicely.

Lord, I hate paint stripping. I think I might finally be done (until I mess up on my new paint job...doh!)
 
Are you mixing it with the reducer (3-parts)? I can't remember the PPG part #.

I use the reducer with DP48LF to prime parts that won't be topcoated. While I won't go as far to say it makes it any "tougher" or "harder" it does make the finish smoother and less chalky and to my understanding, is the only way to get a truly "sealed" finish with DPXXLF primers without topcoating.
 
sf3543 said:
Adding reducer to the PPG DP50 primer mix will make it a sealer, per PPG.
Click to expand...
Thanks for the info. I honestly cannot remember if I added reducer to my primer mixes. Oh well - live and learn.

That being said - that DP50 can be mixed to seal - I'd recommend using it for cockpit interior and under cowl coating. As I used it, it had a semi glossy/matt finish which looks good, wipes clean (of grease and dirt) and is very abrasion resistant.
 
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