Why would my primer be peeling around the edges of where I sanded?

I sanded with a DA: 80 grit, feather edged with 180 grit. Then DA'd the whole decklid 320, then blocked w/320 because I wasn't happy with only DA'ing, especially the edges.

I just painted something with SEM trim black, right before, in the exact same conditions. So I don't think it's due to temperature or humidity.

thats not peeling thats lifting what are you using for primer ???not lacquer is it...?
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Yeah it is. Acrylic laquer. From a popular touch up paint website did you know it was laquer? Whats wrong with using it? Isnt there a way to make it work? Didnt they used to use laquer back in the day?

I used the sem solve prep solvent. Maybe its not compatible with this primer?

The lacquer primer is attacking something beneath. What did you sand and put the lacquer over? Looks like an enamel of some sort underneath.

CustomPaintz wrote:The lacquer primer is attacking something beneath. What did you sand and put the lacquer over? Looks like an enamel of some sort underneath.

I don't know what's under there. It's a 92 Camaro I bought used.. Looks like it's had some sort of body work done.. none of the body lines line up perfect. But the stripes are in a stock location, and they don't line up perfect either.

It bubbled up while I was still laying the first coat. So within about 10 seconds. That picture was about 30 minutes later. And since I took that picture, it has bubbled up even worse than when I took that picture.

When you feathered the edges you exposed some of the base coat. Lacquer based products will dissolve this exposed base and produce exactly what you are looking at. Think about it, lacquer thinner is what we use to clean the spray guns.
You will need to sand that back off and get a compatible primer.

'68 Coronet R/T wrote:When you feathered the edges you exposed some of the base coat. Lacquer based products will dissolve this exposed base and produce exactly what you are looking at. Think about it, lacquer thinner is what we use to clean the spray guns.
You will need to sand that back off and get a compatible primer.

I didn't know lacquer paint acts like lacquer thinner. How come it doesn't dissolve the clear coat? Does clear coat protect against it? I know you can use lacquer thinner to clean off paint scrapes and the paint will be fine. And I thought since I sanded the whole decklid with 320, no clear coat should be left. So shouldn't the whole thing be lifting?

Do you know what paint GM was using back in 92? I'm pretty sure it's urethane 2K BC/CC.

Is there a primer that could go over my existing paint, that will be compatible with my lacquer basecoat and clear coat? I don't mind just stripping the entire decklid to bare metal, but I am hoping to do other repairs that I wouldn't want to strip to bare metal.

Also, do you know if SEM Solve 38374 prep solvent is compatible with lacquer paint? Or do you know any prep solvent guaranteed to be compatible with lacquer? When I called the touch up paint's tech support, they couldn't guarantee any other prep solvents working with their paint, other than their own. But I don't want to wait for them to ship me some of their prep solvent, when I can get any other prep solvent the same day.

It's called edge mapping, amongst other things. As above, it's caused by the thinners in a paint being applied attacking the feathered edges where the susceptible layer has been thinned and surface area increased by the sanding action.

Now to dispel some myths.

Although it happens most commonly these days when an acrylic (1K) is being applied (due to thinners content which I'll get to a little later) it can also happen with 2K products. I've seen edge mapping just as severe as yours when a 2K primer has been applied too thick over a substrate that is susceptible. So, it's not just the primer you're using, it's a combination of things - products, preparation method and application method.

What products are "susceptible? Strangely enough, not other acrylics nor basecoats, usually. Some 2K primers, non isocyanate 2K products are particularly reactive, some finishes used on plastics. Particularly, in my experience, those on GM vehicles (note my location though) and some Korean vehicles, especially Kia before the Hyundai takeover. You can test for reaction by wiping a cloth soaked in 1K thinners before you paint. If it sticks or drags or you can see a reaction then proceed with care.

As you point out, acrylic was "the" product, back in the day. It was used day in, day out, in paint shops across the world with few problems. Why? because there is a technique to applying it successfully and a lot of that technical knowledge is being lost as the guys who used it all the time retire or leave the industry. Using a 1K product is not like spraying a 2K product - you don't just hose it on and wait for the magical result. However, it is a very good system, capable of producing astounding results if used correctly. It has lost favour because, by comparison with the newer products, it is labour intensive and time is money. It (1K) is also less resistant to some chemicals. Some will argue that it is less durable but that isn't necessarily the case.

Before going any further I'll just spend a short paragraph on the product itself. It is relatively low solids content, even primers. So your preparation work needs to be good because you can't rely on the paint to fill imperfections like 2K will do. That said, it can be used in a high build situation if it's applied correctly. When ready to spray the added thinners content varies from 50% to 60%. The base paint (unthinned) also contains thinner so solids content can be down around 20%. What this means is that up to 80% of what you put on will evaporate. So, it is just like spraying thinners on to your substrate.

Knowing this, the key to successful use is to not put it on too thick in each coat and, very importantly, to use the right thinner to reduce it. In the lower coats, i.e. etch, primer, primer/surfacer, base and early coats of clear or finish topcoats, it is important to build the film in thin layers. This lets the thinner evaporate or flash off quickly without forming a skin over the top of a wet layer, trapping thinners inside which can then attack the substrate. Light coats, almost dry, but not quite, are the key and then let it flash before spraying another coat. Even over really reactive substrates this technique can be successful.

When you get to the topcoats you'll need a slightly slower thinner that will allow flow out and high gloss. I often use a retarder in these coats and they go on almost like 2K. At that point you can go a bit wetter, having built up a series of layers underneath that will protect the substrate.

The simple solution for where you're at now is to use a sealer, after allowing the primer to fully dry and rubbing back smooth. Or you can just rub back and go with a series of light coats of the primer you're using.

Finally, your preparation solvent has nothing to do with this. It won't hurt any fully dried paint finish, It is a good idea to use a water based cleaner last thing before painting though.

Thank you for the detailed reply. Now I have a much better understanding of acrylic lacquer paint. Now I see why the thinner in the paint would react with other products.

I have a feeling it is only reacting with the primer that was exposed where I sanded those areas. Because it did not lift on the rest of the decklid where the basecoat is. So hopefully I can get away with only priming the feather edged areas.

Just an idea.. would filling the repair areas with body filler or glazing putty help the primer stay on better? Or would it still react with products underneath it?

Also, how long do I need to let each coat flash? The paint says 5-10 minutes, but the primer was still lifting for hours after laying it down. Their ideal temperature range starts at 70 degrees F. Humidity ideally 50%. Where I live only allows me to paint around 68 degrees F and around 75% humidity. However, I have painted a few things with SEM Trim Black on different days, and it always turned out fine. I found out today from SEM that their Trim Black is a lacquer product as well.

Once I get the primer on good without any lifting, I should have an easier time laying down the base and clear, correct? Since it will be lacquer over lacquer.

I admit I layed the primer on kind of thick. Well, about the same as I did the Trim Black. (Trim Black is pretty forgiving though) One pass of primer across the decklid took me about 7 seconds, including spraying off the lid to the plastic sheeting, at the start and end. Each pass, I overlapped about 50%. First coat, you could barely see the bare metal anymore. Second coat, you couldn't see the bare metal anymore, though you could tell the paint was thin.

This time I will try to spray it in a way where it's almost dry as soon as it lays down.

What kind of sealer can I paint over my 2k paint, that will also be compatible with my lacquer primer/base/clear?

what kind of miracle are ya asking for bub....just strip it an get it over with ...jmho....bondo.even with rattle cans it will be easier...trust me