epoxy over 2k? problems?

U

underdog

I sprayed two coats of slighty reduced epoxy over some 2k that was final blocked with 320.
I allowed proper flash time between coats. The fenders have been sitting for just over 7 days. 90 plus temps in day.

I did my normal fingernail test in several areas and seems to be pretty good, but if i pick in an area long enough i can break through and can pick very small sections of epoxy off at time?

So I decided to block a small section down with some 320 to hit the 2k. Ounce the epoxy was blocked thin enough to show the 2k underneath I performed another fingernail test on the very thin featherd epoxy and adhesion is worse?

Im confused.

(Note) when hit with the 320 the smell of epoxy comes pretty strong. Maybe epoxy is just to fresh for such tests?
 
Sounds like trapped solvents, maybe consider blocking and putting out in the sun for the day and see if that helps.
 
7 days is not fresh, I dont know how projects are supposed to work with some of the drying times that are recommended. Weekend warriors can spray primer last thing on a weekend and get back to it the following weekend. you gotta consider most 2k is a 4:1 mix with hardeners, epoxies are 1:1. Epoxy is made to bite into metal for adhesion with the chemical reaction. If there are not metals there they try to burn into the paint underneath. These are the reasons some epoxies are made to just be sprayed over bare metal. When the solvents are attacking the paint or primer underneath, the activator is not where it needs to be in the epoxy coat. I had the same thing happen with clear that was sent with the more clear in the activator can, made everything soft down to the sealer. There are epoxy primers / sealers out there that are safe over body fillers and other primers, some just want you spraying it over a coarse metal surface.
 
i have yet to have any problems with spi epoxy . read the tech sheets and do as they say. stop trying to reinvent the wheel. spi epoxy reduced 1:1:1 if an excellent sealer. if you spray it wet you end up extending the flash time.
 
Their is nothing soft underneath.
And if this epoxy wasn't meant for over 2k then Barry wouldn't have it as a sealer in his perfect paint job with a reduction 5-50% and that's over 2k.

Another idiot l've read your post on your problems with that situation, this isn't even close.

And two wet coats of spi epoxy in 7 days in my book is fresh.
 
I didn't say it was a problem? I was simply asking a question.

I'm not 100% sure on the adhesion of it over the 2k that is all.

Re inventing the wheel.. somewhere down the line you decided on epoxy only. I would say that's a new invention

I'm not trying to be argumentative, I'm trying to find a system that works for me.
 
when I spray over 320 I use my base gun with it reduced about 10-15%. you may have sprayed it too thick. spray it just like base
 
I guess people consider that picking epoxy off with your fingernail is a problem.

All you have left to consider is induction time and how clean the 2k was underneath it. Did you wipe it with something before spraying the epoxy? did you dry sand or wet sand it, if you wet sanded was it water break free before you sprayed the epoxy. Those are the only things that should make for adhesion problems with epoxy.
 
if you had ever done a test you would understand . 7 days is the open time for epoxy not the cure time.
 
Could you please explain, shine.

I'm not spraying it as a sealer. I want to simply use it as my finial prime over 2k. (Or last light blocking session).

I'm just not familiar enough with the epoxy to know ifs a issue or not.

No one else is trying a finger nail test or equivalent?

Blocked 2k with 320 dry
700-1 a day before epoxy
Induction at least 12 hours.
Tacked it and shot it.
 
I have never tried a finger nail test or any other test and have been using SPI epoxy since 2005 without a problem in my shop.
 
I could be wrong, but I thought I saw Barry mention once that epoxy isn't fully cured/hardened until 6 months or so. I can't find the thread, so I can't quote him on it.
 
I use SPI epoxy as a sealer all the time with absolutely no issues. However I reduce it 1:1:1 using #885 slow reducer and usually just one coat.
 
I was not spraying as a sealer.

I was using for one last layer of primer that would be blocked. To give me uniformity in color.

Only thing that is different than the last time I did this is two different gallons of Grey epoxy. Same reducer temps ect.

This is the gallon I posted about that had the excessive settling when inducing.

Not sure if that had anything to do with it. Just trying to figure it out.
 
underdog;39517 said:
I'm sure full cure isn't for a while.
Click to expand...
Exactly! Until it reaches full cure any adhesion tests before that point are not valid. There's a a lot of things that will affect the rate of cure.
 
all the epoxies will settle after acc . no epoxy is going to be full cured in 7 days . using 2 coats of epoxy over 2k for blocking is backwards. epoxy mixed 1:1:1 will shoot like base. 2 thin coats then base in an hour.
any any of them will scrape off in the first week or so.

- - - Updated - - -
 
So what is it, exactly, that you want to know? Whether or not you should be able to pick 7 day old epoxy with a fingernail?
 
I just wasn't sure about the "tests".

Like I said I'm not used this epoxy long enough to know if it was a problem or not, I always perform a fingernail test in a small area after a few days just to see how adhesion is. And this seemed softer than in this in the past.

The real question is: is their a problem with epoxy over 320 2k as a final prime?

I'm not an expert and don't claim to be one. But I see an advantage using epoxy as a final prime.

Just trying to figure out a solid strategies that work for me.

Mitch. In a nut she'll. Yes.
And Bob your exactly right but temps have been hot! And I figured after a week it would have been a bit more solid, that's all.
 
I keep seeing you write final prime. As I see it, it doesn't matter whether your "final prime" is 2K or epoxy, as long as it's smooth and you seal it with reduced epoxy before base. You could sand the epoxy smoother and, as long as you don't break through, go straight to base, but I think a coat of sealer would still be best because it gives you chemical adhesion as well as physical to the base vs just physical from the sanding. If I'm wrong, hopefully someone will correct me. Honestly, asking Barry would probably be the fastest route to the correct answer.
 
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