Cracks in the paint

[Franksredpt]

I've painted many parts for my PT over the years and never had any problems. Lately, I've been trying to paint some parts for my new car and keep running into problems. I'm painting splash guards. I primed them, added 3 coats of paint and clear coat. When I add the clear, the paint will crack in about 2 minutes. I sanded off the paint a few days ago and reprimed and repainted. Went out this afternoon to add the clear and once again the paint cracked. I got the front set painted with no trouble, but the rear set is driving me nuts. All parts were cleaned with alcohol and the temperature has been in the 70's all week. I waited 2 days between the last coat of paint and the clear. I'm running out of patience and paint.

[Cartman]

Are you using a plastic parts primer or a standard primer with flex agent? some plastics are especially a pain in the a$$ when it comes to painting. clean the part with soap and water first, then a plastic prepping/cleaning paste (dupont, SEM, PPG all offer some kind and are available at parts stores that have paint) then scuff using waterbased wax and grease remover (prefferably made by the same company as your paint system). use a waterborne plastic primer. these are usually 1K primers and are nonreactive to plastics. once that primer is dry, you can go over it with standard flexiblized sealer and base/clear. dont wait too long between base coat and clear coats. the most dry recoat time ive seen with paint systems is 12-20 hours, any longer than that you will have delamination problems with the clear down the road. saturns have plastic parts that are a pain like this, but when you prime with that waterborne, you have no issues. good luck and hope this helps.

[lakersfan1]

Agree with Cartman. Plastic parts usually have alot of mold release on them, which is going to act like a grease. The primer and color will usually go over OK, as the wax or grease will just pull to the top of the paint. But once the primer is applied to try sealing it in, it'll look like ass.

Open the phone book to find an Automotive Paint Supply shop. This will be who your local body shops buy paint from. They should have a full selection of SEM products, which include a plastic scuff cleaner, a plastic dewaxing cleaner, and then the plastic flex spray that you'll need to spray just before the initial primer layer.

About the waiting two days between color coats, usually that's OK as long as you wetsand the project first. Check the material data sheet for your paint. But this is not the reason for your troubles.