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Targa Time's Avatar
 
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Paint won't dry!

I am currently finishing up a engine rebuild on my SC and thought that it would be a good time to freshen up the engine compartment being the engine is looking so good.

I am not a skilled painter, or painter at all for that matter. So I went to the local auto painter supply store, explained my project, and they provided me with color matched paint in a aerosol can and a can of primer. (SEM self etching primer)

Following directions I cleaned, primed, waited 1 hour and painted the engine compartment. 24 hours later parts of the painted area were dry and others wet to the point of coming off on your finger when lightly touched. The paint was only wet in the areas where the factory undercoating was.

I waited another 24 and it was still wet. So I tried a heat lamp for about 6 hours. Still just as wet as before. At this point I'm running out of ideas and the paint supplier was no help, so I cleaned off a wet area, primed with Rust-Oleum auto primer and painted again. Same issue, still wet.

As a last ditch effort I cleaned, primed and dust coated with paint. Tacky after 24 hrs.

Any help or suggestions would be greatly appreciated.
Old 05-14-2011, 07:10 AM
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Not all paint types are compatible. I have had similar issues in the past trying to refinish parts with aerosol cans. Paint has either stayed wet or cracks almost immediately.

It is also possible that the primer is reacting with the undercoat or even whatever you cleaned it with.

If it's not dry by now it never will be. Unfortunately you'll need to remove it and start again. It is tedious but necessary for a quality job.

Others will be able to recommend specific products but you might want to consider using 2K paint rather than an aerosol. An aerosol obviously has no hardener and so the drying process can be easily reversed with chemical spills. Oil, fuel and many cleaners will just ruin the finish so I wouldn't recommend for an engine bay. Some aerosols can be baked to create a chemical resistant finish but this is not practical for what you are doing.

2K for the engine bay is not that hard to get a good finish, no harder than an aerosol once you practice the gun setup - a piece of scrap is a good testing ground. You just need a clean surface and mask off well so you don;t get overspray everywhere.

Maybe you can borrow or hire the equipment. I think it's worth considering.
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Old 05-15-2011, 03:10 AM
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2k ?

thanks for the reply.

What is 2K paint. Is it a brand name or a type of paint? Ill need to know when I go back to the auto paint supplier for paint.

I used 2 different primers and had the same results with both. That leads me to believe that the undercoat is reacting with the primer and then the paint even though the primer dried hard.

Do you think that the paint in areas where there was no undercoat and it dried hard, will be affected by gasoline vapor/ gasoline spillage?

Thanks
Old 05-15-2011, 05:08 AM
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2K paint (or 2 part) is what you mix up with a hardener and often a small amount of thinner, so it's a type of paint not a brand. By mixing you start a chemical reaction that will dry the product to a very durable finish. It's the same stuff that a car's exterior is painted with.

2K comes in a couple of formats; single stage which is simply a matter of mixing and applying the paint, or 2 stage which has a base (color) coat and then clear applied over the top. If your car is non metallic then single stage is fine (and it's much cheaper as you use less product). Even for a metallic paint, single stage can be OK in the engine bay but everyone has their own opinion.

Is the primer drying after you apply it? Are you allowing enough time for the primer to dry. If you apply wet paint on wet primer then you can similar issues. If you are cleaning with wax and grease remover then you also need to let dry so that some of the residual can evaporate. When using a cleaner it's advisable to use lots of rags to make sure you get all the excess off.

I doubt vapors will harm the paint but spillage can.

Going back to basics I would make sure you are following the instructions for the primer and paint - including drying time between coats, ambient temperature ranges. I would use the same brand paint and primer as they will be designed to use together.

I have very little experience painting and was a bit nervous about using 2K. It was alot easier than I thought. As I mentioned in my original post, preparation and proper masking is essential, the painting itself takes very little time.

If you are unsure what to do next go back to the paint supply shop and tell them what is happening. Surely they can get it sorted out for you.

Good luck with it.
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Last edited by D911SC; 05-15-2011 at 01:19 PM..
Old 05-15-2011, 01:15 PM
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If you go the 2k route be careful. One type of 2K paints use isocyantes for the hardener and unless you have a suppiled air respirator, you can quickly do some real damage to your lungs and other bodily parts. Be sure to check with the guy at the paint counter so you know what the hazards are.
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Old 05-16-2011, 10:19 AM
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Thanks HarryD

Thats a good thing to consider. I'm still not decided on what to do. This engine compartment paint was a "while I'm in there item" secondary to the engine rebuild. When I got into it I thought it would just be a matter of a spray paint touch up. I should have known better after owning Porsche's for 36 years.

I've already spent WAY too much money on the engine rebuild. So the thought of purchasing a paint gun, respirator and who knows what else by the time its done is not too appealing to me. But at this point I have not as of yet come up with an alternative.
Old 05-17-2011, 05:07 AM
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harry any paint vapors will kill you ! isocyanates are used in 99.9% of all sprayible products polymers , paints , lacquers and so on ! even in the spray can you have ! there is just more of it in a catalyzed sprayible product but not a hole lot more . you should use a charcoal respirator when spraying ANY finish ! IT WILL ALL KILLL YOU !!!!!!!! targa time from what i'm getting is that your finish is not drying only over the under coated areas . that tells me that the under coat may not be of an OE type ? but a black rubberized type ? what color is the under coat your going over ?
Old 05-24-2011, 05:12 PM
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962porsche:

I totally agree that the solvents in just about any paint need to be handled with care (i.e. minimize exposure, carbon respirator, gloves, protective clothing etc). It is just that the ones containing isocyantes demand a higher level of care.
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Old 05-24-2011, 05:48 PM
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