Hello everyone ,


I'm new to the forum and I'll be happy to answer any questions about Automotive Refinishing, Exterior Repair, Custom Matched Paint or body work. My goal is to educate as many people as I can in my field of expertise.This is sothey can get the results they want from a DIY exterior repair.


Feel free to contact me anytime.


-Mike

 

If it's not too difficult, I would appreciate a summary of the proper procedure to refinish flexible plastic bumper covers. In particular, I'd like to know the best way to get adhesion, and make the paint flexible.

 

Before I can give you detailed instructions please answer this question:


1) Is it from the factory, unpainted, black raw plastic?


Each answer to this question will take us down a different path.


Let me know


-Mike

 

Yes; new piece, raw from factory. Edited by: MrBSS

 

Ok, here are the steps:


*****OEM BUMPER REFINISHING*****


1) Clean well with hotcarwash soapand water and allow to dry


2) Clean with a Grey Scotch Bright Pad (3M.7745), and wax and grease remover (FIV.5900) , Plas-Stick Universal Plastic Cleaner (DUP.2320S) , or if you're really on a budget; rubbing alcohol will work after a few applications. To test if you've cleaned it enough, sprinkle some water on the surface. Does it stick or run off? If the water sticks you've done a good job and the part is ready to be painted. If it runs off, you need to use the solvent based cleaner again. At this point you've removed all the water based contaminants such as dirt and dust as well as all the solvent based contaminants such as oil, grease, wax etc.THIS ENSURES GOOD ADHESION


3) Spray flexible primer (SEM.39133) on the entire piece. Try to make the surface as evenly coated as you can. The goal while you are coating any area with primer or paint is to achieve "hiding". Hiding is a term which means "The minimum thickness at which a film will completely obscure a black and white pattern". Basically, till you can't see whats under it anymore. In this case, you will apply primer till you achieve hiding over the black plastic. Wait 10 minutes between coats and about 45 minutes for it to become sandable.


4) Lightly wetsand the area with 1000 grit sandpaper (3M.32021) . "Wetsanding" is a great technique which helps smooth the surface, and eliminates primer dust in the air. This will help you later when you start to coat with your basecoat paint. Drysanding actually makes sandpaper behave like a more course grit. This is because without a flow of water, the grits that come off the sandpaper and the primer dust all stay under where you are sanding. As you sand you are rubbing those grits against the surface too. Using water makes the paper act more true to its grit. Wetsanding is done by sanding in a continuous flow of water. This can be done with a garden hose or a wet sponge and bucket of water. In the garden hose technique, you simply hold the hose in one hand and sand through the stream with the other. With the sponge technique, you frequently dunk the sponge in the bucket of water and squeeze it above where you are sanding, creating a flow of water. Using a hose, however, is much easier.


5) After the surface has dried, you are ready to paint with your basecoat (www.paintworldinc.com).Apply 2 - 3 even, medium wet coats till you achieve hiding over the primer. Some colors cover better (White) and others take more coats (Red). Adjust accordingly. Whileeach coatis wet, a good way to tell if you have enough on the surface is if you can clearly see yourself in it. This means thefilm is smooth and even and it will stay that way as it dries.Don't apply too much though, you'll run or sag the paint. Again, 10 minutes between coats and about 45 minutes to dry. DO NOT SAND THE BASECOAT. If you are using a high quality 2-stage Urethane like ChromaBase, you do not need to sand between coats of paint.


6) Apply 2 - 3 even, medium wet coats of clear (DUP.A7480S) . Yet again, 10 minutes between coats and 45 minutes to dry.


Congratulations! You've just finished painting your bumper!


Just a couple moretips:


DO NOT wax, buff, compound, or go to the carwash for 30 days. This waiting period will allow the paint to fully cure and get to maximum strength. If can't wait for a showcar shine, use a good glaze (3M.5990) on the area. Glaze will give you a temporary shine while you wait. If it rains you will have to reapply the glaze.


I hope this helps you as well as anyone else that reads it.


Sincerely,


-Mike


Edited by: PAINT4CARS

 

Hey, thanks a lot! That's great!


I'd also appreciate a short explanation of conventional spray guns vs. HVLP, particularly on the above project. I have a conventional gun from years back, and recently got an HVLP because that seems to be the way things are going. However, I don't really know the advantages or disadvantages of each in my situation.

 

Honesty, you can do this job out of spray cans if you really wanted to but if you have experience with using a gun then more power to you.


To answer your question, a gravity fed HVLP gun will always be your best bet no matter what job you are doing. HVLP is better technology, has a high transfer percentage, better flow and in the end a better finish. The process with a spray gun is essentially the same, except the different materials will come in liquid form and you will have to do a little mixing of different components, reducers, etc. Will the job come out better from a spray gun?...Absolutely, provided that the painter is skilled enough. If you're not sure of your painting skills however, I would go the spray can route. Theres more margin for error.


Let me know what you think.


-Mike