I just applied a layer of paint to my car hood. It started to crack almost as soon as it was deposited. I used an aluminum primer from Rustoleum (cheaped out) as the substrate for the paint. The paint was from AutomotiveTouchup. On the phone they said it was urethane -based.

Is there any fundamental chemical incompatibility between these layers? This is my second go-around with the crackling. I made sure there was no water or oil at the interface between the paints.

Thanks
Tim

Rustoleum.....can we please just stop using this stuff on automotive! It was in NO WAY compatible with the urethane you sprayed over it. You have to stay within "paint" systems to avoid catastrophic failures like this. Epoxy primers, 2k high builds, base coats, and clear coats. That is a sound system. Epoxy primers, 2k high builds, and single stage urethanes. That is a sound system. And even, yes, lacquer primers, lacquer topcoats, and lacquer clearcoats. That too is a system (although rather outdated and of limited wear/tear.)
RUSTOLEUM rattle cans + anything= Not a system.....

Jay D.

OK, I understand the resistance to Rustoleum

Just to be clear though, are there any general rules as to what makes a system? For example lacquer doesn't play well with urethane or epoxy and acrylics always go together. (I'm making these up just to illustrate what I'm asking - not saying they are meaningful). I've seen some compatibility charts on the Internet but just wondering there are any rules of thumb.

Okay, try this.... it's easier.....stand in front of a mirror and say, "I will not put anything on my car that comes from a big box hardware store." Instead, seek out a good local automotive paint jobber. PPG is big around me and we still have some knowledgeable old timers at a few of their order counters. Get some product sheets on some of their paint lines like Shopline, Deltron, etc. They will lay out in black and white what can go on within that line.
As far as what you are trying to do about "generalizing" about compatibility, I think that's quite difficult. The big problem with your favorite Rustoleum rattle can people is they make both enamels and lacquers in those cans and if you don't know how to read an msds sheet you don't "see" the chemistry that makes one product a long oil air drier and the other a simple solvent based material, boom!

DarrelK wrote:As far as what you are trying to do about "generalizing" about compatibility, I think that's quite difficult.

Agree 100%. Even with many years of experience (and a few classic stuff-ups along the way) I still constantly refer to the TDS and make the odd phone call to the distributor or manufacturer. Much quicker and easier, apart from cheaper, to do that than it is to guess and then have to re-do the whole job.

^^^^^^Amen to that... we sometimes get involved with industrial, craft, or conservation projects where the "people in charge" just start name dropping products and how they want them applied. I'm always pulling sheets on stuff because I can't assume it will all work together just because someone behind a desk says it will........

Know what you mean. I have a Request for Quote in my email right now where these people want plastic boxes sprayed with Rustoleum spray can primer.....5 coats of it! No top coat, for use in exterior electrical applications.

I've emailed them back to say that we can do it properly and guarantee the work or they can find someone else.

Wow.... and how long did they thing that crap would last? Just primer..... Well, so we have established that Rustoleum is a worldwide aerosoldemic......

DarrelK wrote:Rustoleum is a worldwide aerosoldemic......

It gets better. There are 100 of these boxes and covers. 5 coats, 2 hours between first and second coats and sanding initially and then after first coat. The classic line was

Each Junction Box set should take about 5 minutes actual labour time (not including drying time) to complete. So 100 x ~5 minutes = ~500 minutes total (about one day’s work – I hope you have some spare time available?)

So the setup time for 200 items to be painted inside and out, as well as the time between coats we get to do for free?