First time painting, 3 new panels, priming help!

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PostPosted: Sun Mar 10, 2019 7:59 pm
Okay so title is a tad of a misnomer, I’ve tried my hand at painting a couple things but it was touch up with rattle cans. Specifically, some touch up work with a can of NAPAs crossfire custom rattle can. The body work I did underneath (which I hadn’t done before) came out like garbage but the paint actually looks good still.
Anyway, I know the car has been painted with that same product before so I’m looking to stay with the Crossfire Singe Stage – I’m aware it’s not the best product or will give the best look but with a little bit of polishing I think it looks great and this way the new panels match the current paint job. I also happen to have a little of the previously used paint leftover – probably not enough to do all three panels but enough for one at least.
So, I have, like I said, three new panels. Two plastic bumpers and one metal fender. I’m planning on doing them one at a time starting with the fender and I’ve got a few questions. Firstly on primers and priming. These are brand new OEM (Mazda) panels. Everything I found said I need to sand off the factory coating on the fender (metal), prime and paint. I can’t find a straight answer on the plastic bumpers though about what I need to do to prep those. The parts listing says primed but are they really ready to just shoot paint?
Assuming I need to prime all three first I’d like a good recommendation for a fairly low cost primer, and if I don’t need to prime more than the fender (which I’ve already sanded so I definitely have to) is there a rattle can option that’s usable or should I just get a small amount of something to mix and spray?
I’m also curious if I need to do multiple primer coats and how to go about that. Some things I’ve seen say spray the whole thing twice but all at once (like spray it top to bottom and the spray it side to side as soon as you cove the panel) other say to spray and let it dry then sand and prime again then sand a spray paint and some say to spray primer, let it dray a few hours – but not TOO long and then shoot paint. I’d rather not do this three times figuring out the right way and I’m hoping that someone here will be kind enough to unload some of their vast wells of knowledge on me.

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PostPosted: Mon Mar 11, 2019 10:44 am
Hello and welcome.

How old is the paint that is on the car now?

If your paint has been properly stored in a consistently cool place, it should be good.

For the fender, if the company wants you to take off the coating they have on, then take it off. Finish the fender off with 150 grit or 220 grit (I'm unsure how soft new metal is), wipe clean with microfiber towel and air at the same time. I have found that wax and grease remover over metal causes terrible adhesion. You can use a epoxy sealer over the bare metal for adhesion. (When your ready for paint)

The bumpers, WET sand those with a grey scotch-brite, any kind of dry sanding will leave "hair" like plastic sticking up off the surface and looks terrible. Then there is a product by SEM that is a plastic adhesion promoter (when your ready to paint).

When your ready for paint use epoxy sealer for the fender (thin-ish coat with lite transparency) and your plastic adhesion promoter on your bumpers (will be clear), allow flash time typically 10-20 min based on temp, then apply your sealer on all 3 parts that's compatible with your paint, wait flash time again then paint.

Make sure to get or print out MSDS sheets for all the products used. They will provide all information you need from mixing to flash times to how many coats and how thick. also what other materials they are compatible with.

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PostPosted: Mon Mar 11, 2019 11:08 am

Just an FYI but we do have a Fiberglass and Plastic forum that covers the many questions dealing proper repair, prep and painting of these materials.
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PostPosted: Mon Mar 11, 2019 11:55 am
i believe there is a spraymax 2k epoxy primer in a rattle can and from what i saw in videos, is a viable option where no real cleanup is needed. i bought a few off of ebay. i would think at least 2 coats and wash it down with 400 before base.

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PostPosted: Mon Mar 11, 2019 1:10 pm
The paint on the car is about 2 1/2 years old and the left over is from then. It's been stored in the gallon can it came in, tightly sealed, and kept inside in a basement closet. I would assume it's still good but I'm not actually sure, or entirely sure how to tell, now that it comes to that.

As far as the coating on the new fender, I did go ahead and sand it down, I couldn't find a definite answer if it was paintable or not as is but I figured sanded and primed metal is always paintable. I ended up using 320 paper but I can go back and hit it with 220 if it needs a rougher cut for good adhesion.

Which leads me back around to the primer kind and application question, what to use and how. Sanding with 400 before final painting makes sense and two coats sound good but is it like a double wet thing or once then dry and sand and then again or spray and then spray again?

Is the epoxy sealer you talked about a kind of primer or something you spray on before priming or between priming and painting?

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PostPosted: Tue Mar 12, 2019 12:29 am
Pyrannha, unfortunately there is both good and some very bad advice in the preceding answers to your questions.

Let's start again.

The coating on metal replacement panels is e-coat. It is applied with an electrostatic process in a big bath and is chemically cross linked to the metal. The finish is near perfect and is perfectly suitable to just go ahead and paint over, after a thorough scuff with red or grey Scothbrite, depending on whether you're base coating or priming. Believe me, no manufacturer would go to the trouble of investing in very expensive tanks and ovens if they intended that coating to be taken off. Might as well just give the panel a spray with some WD-40 and wrap in plastic.

There are different kinds of e-coat but they all do the same job and regardless of whether you can take it off with thinners or not, it is suitable for painting over. The problem, however, is that it's thin at about 10-15μm and this means it has no cushioning ability to withstand impacts. For this reason most shops will prime over the e-coat so that the primer becomes the cushioning layer.

So by removing the e-coat you have compromised its ability to protect and made yourself a lot more work. Hopefully you'll use an epoxy or good DTM primer to get back that corrosion protection you just sanded off.

Epoxy is the best rust protection that you can apply and doesn't need to be thick. One or two even coats will do the job, After anywhere from 20 minutes to a few days you can apply a primer without the need to sand. Once the primer is cured it will need sanding. Do NOT use P400 as your final sanding process before finish coats. Use P600 wet if you are painting a solid colour or P800 wet if the colour is metallic or pearl. P500 dry on a random orbital sander is acceptable as an alternative.

Now, the bumpers.

There are a few different processes for priming plastics and these vary by manufacturer and by plastic type. The obvious one is where the plastic is primed with a paint, usually sprayed on It should be easy to tell if this is the case since it will usually be a different colour and you'll see where it finishes around the edges. Sometimes the finish can be outstandingly smooth, but it will always feel different to the unfinished plastic on the back of the bar. Scuff with grey Scotchbrite. It makes absolutely no difference whether wet or dry, but the poster was correct about not using sandpaper, since that will tear up the edges of the scratches. Wash well with soap and water, rinsing thoroughly. Dry, tack and proceed with finish coats. Using a plastic adhesion promoter over a primer is ridiculous.

A newer type of finish is one that's been flame treated. It looks a little duller than the back and feels different. Very good for adhesion though. Wash thoroughly and dry, then prime and paint. Some say you can apply 2K finish coats direct to this finish. I'll believe it but prime anyway.

Then there's bare plastic. There are two kinds - good and bloody awful.

OEM's nearly always use quality resins and their plastic bars, even unpainted are smooth, even and do not retain oils used for mould release. These bars should be washed then treated with an alcohol solution (no, not your wife's favourite brandy) and then washed again. Scuff with red Scotchbrite, but evenly with the flat of your palm, because even that grade can tear up the plastic. I like to wash a final time and even go over again with the alcohol solution to remove any residual traces of oil or grease. Then prime and paint. You can use an adhesion promoter before the primer if you wish, especially if you're not familiar with the primer that you're using.

Oh, the awful ones? Usually coming from 3rd world countries, via Ebay or similar, they generally contain a mix of recycled plastics and very cheap resins. Rarely fit properly and the plastic is extremely porous so the mould release agents soak deep into the surface. They can be a nightmare but most major paint companies have a special primer for them which requires special preparation usually involving heat, alcohol, water and detergent. Follow the instructions to the letter if you don't want the paint to fail.

What's the alcohol solution? We call it methylated spirits and it's about 95% ethanol. Forget what you guys call it, rubbing alcohol or something, although why you'd want to rub that stuff on yourself I have no idea.

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PostPosted: Wed Mar 13, 2019 6:41 pm
Sucks that all the fabulous information you gave me wasn't more readily available but thank you very much.
i did unfortunately sand off most of the e-Coat but i got a good DTM primer so i'll be using that and then painting over and we'll see how it looks.
I haven't yet taken a good look at the bumpers as they are put up and away right now - i'm doing the fender first - but I'm willing to bet they are bare plastic. They came straight from Mazda so i'm not worried about them being cheap but on my original quick inspection i didn't see them being spray primed or anything.
I did pick up some adhesion promoter for those as well
so current plan in spray a couple coats of primer, sand with 500 on my DA sander and then spray paint (it is a black metallic) on the fender and then on the bumpers i'll be using the wash, alcohol, wash, scotchbrite, was,h alcohol, adhesion promoter, prime, paint method you suggested.
I'm exited to give this all a try!

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PostPosted: Fri Mar 15, 2019 1:20 pm
RestoRick wrote:Make sure to get or print out MSDS sheets for all the products used. They will provide all information you need from mixing to flash times to how many coats and how thick. also what other materials they are compatible with.

No, A Material Safety Data Sheet (MSDS) is a document that contains information on the potential hazards (health, fire, reactivity and environmental) and how to work safely with the chemical product. It is an essential starting point for the development of a complete health and safety program. This Document is a controlled and regulated by federal agency's (OSHA for one) and provides specific information about a chemical products.

Technical data sheets are NOT MSDS sheets! Technical Data sheets Provide the necessary information you need for using the Product, for Paint it will include information such as mixing to flash times to how many coats and how thick a coating should be, Air Pressure to be used while applying it too suggested Paint gun Fluid tips size etc. and what other materials they may or not be compatible with, and some other info depending on the MFG and what they feel like telling you about how a Particular product and how it should be used and vary from one manufacture to another and is not a controlled document!

That said some dealers and manufactures are combining the information in one place but they are two different things.
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