Paint Gurus, a few questions

Posted By: Crazy68Dart

Paint Gurus, a few questions - 09/30/08 11:13 AM

Looking for some help from paint/body guys that do this day in and day out.

So the body/paint work on the Dart has started. I have been doing a lot of research on the "proper" method of priming and painting. It looks like the recommended method is strip to bare steel (which I want to do anyway) and do the metal work. Next, use an epoxy primer for corrosion resistance. After that, scuff, do any body work and high build priming. Get everything pretty, and as a final step before the base coat, use a sealer of some type over the high build primer and body work. Does this make sense?

Few questions...

Can etching primer be used in place of the epoxy primer? Yes, no, and why?

Is a sealer before the base coat really necessary? Yes, no, and why? Understood it seals, but is the reason this is necessary is that the high build & body work is porous, or are there other reasons?

Thanks all!

Posted By: 6T6Cuda

Re: Paint Gurus, a few questions - 09/30/08 11:38 AM

Hello,

While not a pro; here is what I think and understand.

You can go direct to metal with the epoxy w/o an etching primer. One disadvantage of an etching primer is you can not do body work (i.e. bondo) over it; whereas you can with epoxy (and it is recommended in general).

If you use an etching primer you need to put it down, then spray epoxy, then do you bodywork, then primer serfacer (i.e. high build primer), then sealer, then basecoat, then clear coat.

The sealer does a couple of things:
1. It can get rid of very small scratches (320 type scratches) and give a good surface for the basecoat.
2. It provides a consistent color under the base coat, to ensure the colors show up correctly.
3. It seals the porous high build primer from allowing the generally non-activated basecoat from soaking through causing dye back - which cause blotches in the paint color.
4. If used correctly it provides some level of protection for small areas where you might have poked through to bare metal while blocking - you can not just put basecoat on bare metal (use good judgment when doing this).

That is what I know and have gathered in doing this.

Posted By: Mr T2U

Re: Paint Gurus, a few questions - 09/30/08 12:49 PM

i do this every day and i am PPG certified for around 20 years.

6T6 got it right with his answers.
one thing i would do is use self etch AND epoxy primer. spray the etch on bare metal and let it dry according to directions. then apply the epoxy.
the reason i like to do things this way is past experiences. when working at a GM dealer i was painting 15 delamanation complete paint jobs a week for 4 years. on the ones i did when the delams first started i skipped the etch and just epoxied them. i had 4 or 5 comebacks for rust forming under the paint. after i used etch i never had that problem.

Posted By: sixpackbee

Re: Paint Gurus, a few questions - 09/30/08 01:33 PM

Quote:

Can etching primer be used in place of the epoxy primer? Yes, no, and why?

I use DuPonts 615 VariPrime on all bare metal. Etch primer has a superior corrosion protection. After it dries, usually under an hour I go over it with a 3 part urethane primer, Matin Senour's Tech Prime line. Then do the filler work over that.

Quote:

Is a sealer before the base coat really necessary? Yes, no, and why?

I finish sand with 600 wet prior to final color so a sealer is not needed on an overall job. If you are dealing with older paint in spots on the job then sealing is recommended.

Posted By: cataclysm80

Re: Paint Gurus, a few questions - 09/30/08 01:48 PM

good info here, thanks guys!

Tav

Posted By: CJK440

Re: Paint Gurus, a few questions - 09/30/08 01:57 PM

I used PPG DPLF over bare metal and as a sealer when thinned appropriately.

I put Epoxy over bare metal, filler, then seal just the filler, then surfacer, block, then seal one last time, then base.

I never used etch but that doesn't mean anything. I'm just a shadetree body man.

Posted By: fury4speed

Re: Paint Gurus, a few questions - 09/30/08 02:33 PM

Second the PPG DP. They have very good adhesion to bare metal.

Posted By: 70gtx440dana

Re: Paint Gurus, a few questions - 09/30/08 03:07 PM

Not to highjack the post but is there a recommended do it your self book/manual out there for body & paint work? I am beginning my first body project and will have many questions similar to the above.

Posted By: Crazy68Dart

Re: Paint Gurus, a few questions - 09/30/08 04:35 PM

Thanks guys.

I really appreciate it, keep it coming.

Posted By: CJK440

Re: Paint Gurus, a few questions - 09/30/08 06:14 PM

Quote:

Not to highjack the post but is there a recommended do it your self book/manual out there for body & paint work? I am beginning my first body project and will have many questions similar to the above.

In my experience I didn't find books as helpful as other resources espeically with everchanging product lines and EPA regs.

The net is great, guys on Moparts helped me greatly as did this forum.

http://autobodystore.com/forum/index.php

Most important is to find your local paint store and bend the ear of the guy behind the counter. If he's not going to give you the time of day, move on.

Posted By: Geno

Re: Paint Gurus, a few questions - 11/23/08 03:30 AM

This is a down and dirty explanation hope it helps.

Always try to stay within a system. Read the tech sheets on the products you are looking to use. Always do a spray out to check color. And take a trial run before painting the real deal. When all else fails ask the distributor, call a tech line for the paint company or try to contact the local rep.

Etch or wash primers � Go direct to bare metal and assist in adhesion but are mostly there to serve as a conversion coating to prevent a rock chip from getting out of control. Do not put over filler. Do not put filler over.

Epoxies � Can go direct to metal and work well by themselves. There is debate as to weather it is best to put over an etch or not, personal preference and experience. I have done both ways with success. Can go over body filler and body filler can go over epoxies once the epoxy is properly prepped. Epoxies can also be used as a sealer. That said you can put urethane primers over them or under them and color can also be put directly on them as well. Watch your dry times epoxies are slow. Epoxies also have little filling capability but with a couple of coats they can prevent corrosion quite well.

Urethane Primers � Must have a etch or epoxy under them except for small (quarter or style line) cut troughs. Some companies recommend a sealer some don�t so follow manufacturer recommendations.
They can go directly over body filler (180 is the coarsest grit scratch I am aware of) but body filler should not be put over them (some glazing putties are okay). They will not prevent moisture from saturating through to metal so don�t put a car outside and allow it to soak wet sanding is okay. Also they are not body filler!!! 3 coats let it dry and sand it add more if necessary and watch flash times. A good filler primer builds 4-6 mils a crisp dollar bill is 2 mils thick and new OEM paint jobs are an average of 4-6 total.

*DO NOT USE LAQUER PRIMERS!!!

Sealers � Some companies do not require. They will fill at most a 320 grit scratch. They are meant to go over primer and cover very very small cut throughs (to metal or filler) and help with the porosity of primers for better color hold out. It also makes for a uniform color to go over resulting in faster hiding and better color uniformity. Some companies use colored sealers and some use various shades of grey and both work.

From here on all you have to do is pick a color and decide if you want to spray basecoat clear coat or single stage!

Also make sure to wear your Personal Protective Equipment!

Good luck.

Geno