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Old 07-05-2007, 02:48 PM
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Urethane 2x primer on bare metal

New here. I in the process of preparing to refinish the roof of my 98 Dodge Dakota I managed to bring out some metal (sanded too low). Since I hit metal in a few places (near windshield under and in front of windshield top gasket rubber strip)(about 3 square inches total so far), is it absolutely necessary to prime these spots or, worse yet, the entire roof with Epoxy primer, before the 2x Urethane primer is laid on? Will I be safe without Epoxy primer in these areas or do I really need to lay down a coat of Epoxy first? My paint color is black, PPG DBC Urethane, with Advantage 2x Clear.

I painted one other car in my life and it was a lot of car inside and out, every single piece, of a 1955, 210, 2-door, Chevy Station Wagon but I used Acrylic Enamel with Urethane clear on top. That stuff is easy to work with but this DBC is not.
http://55chevy210.homeip.net/55chevy...28/default.asp
http://55chevy210.homeip.net/55chevy...catalog_ad.jpg

Thanks,
Abby

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Old 07-05-2007, 02:54 PM
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I think you should obtain and use the epoxy. You're bound to expose more bare metal as you sand down the rest of the roof. You'll be glad you have it.
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Old 07-05-2007, 02:59 PM
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Do you think a store-bought shaker can will work or should I go for the expensive 2x stuff? I'm losing time on this truck. It's my son's and he needs to get it back. If I do the 2x Epoxy, what is the average cure time on it before I can squirt Urethane primer on top? I'm in Texas and it's hot, muggy, and raining all the time. Humidy is high, temp is high, and air flow is low.

How long do you think it will last if I don't go the Epoxy route?
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Old 07-05-2007, 03:40 PM
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I found a shaker can of Duplicolor Etching Primer at AutoZone for $4.95. I hope this will work because the other stuff is nasty and a lot more expensive for what I need to paint.

Thanks for your advice and I will tkae that route and hope, nay, pray for the best.

Abby.Normal
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Old 07-05-2007, 10:11 PM
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Some urethane surfacers are designed to be used as a direct to metal primer and although they don't have the durability and adhesion of a quality epoxy primer it will work fine over small areas where you sanded through. Check with the surfacer manufacturer to see what they recomend on small sand throughs. Some epoxy primers like SPI actually work well as a surfacer when high build isn't needed-this works really well especially when dealing with sand throughs. I wouldn't use an aresol self etch primer on anything expected to last-JMO. Bob
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Old 07-05-2007, 10:51 PM
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I have never found that taking the easy way out was ever the "easy way out" . I usually causes more work in the long run.

I would think that the rattle can etch primer is going to cause some sever problems to any substrate that comes in contact with it.
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Old 07-06-2007, 12:16 AM
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Thanks to all that replied. I am going to take back the rattle can of etch primer and go with the Urethane primer on the bare metal. I will scuff it up with some 50 grit to give the primer something to grab hold of first.

Here's the plan:

Wet down the concrete floor with water to hold the duct down to a reasonable level. Ground the truck to the water line with AWG10 wire to help with the static from the gun ionizing the paint.

Dry surface, wipe down with PrepAll, tack rag it.

Spray on a light coat of Urethane primer over entire surface. Wait a couple hours and block it all off smooth with some 400 wet. Spray on another light coat over entire surface. Wait about 2 hours then block it with 600 wet.

Dry surface, wipe down with PrepAll, tack rag it.

Spray on a light coat of color (black DBC Urethane). Wait about 45 minutes then squirt on another light coat of color. Verify entire surface is covered. Should dry to satin finish. NO BUBBLES or CHEMICAL POP ALLOWED!!!!!!

Wait a couple hours and block if required to remove dirt and dust (use 1200 wet in a left-to-right motion only). Dry, wipe with PrepAll, then tack rag it all.

Verify water on floor for dust and grounding is still in tact.

If the color needs to be blocked do so and hit again with color if required.

Block with 1200 before squirting clear if dirt/dust is obvious.

NOTE: Only 2 light coats of color and 2 light coats of clear if possible. No more.

Does that sound like a viable plan? If not, please advise as to where I am going wrong. The paint will start to flow Saturday morning after I get the old finish off to the original OEM primed surface.

Thank you all in advance,
Abby.Normal
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Old 07-06-2007, 05:38 AM
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Your plan will work but I'll offer up another option for consideration. Instead of priming twice you could easily apply two coats of primer with 20-30 minutes of flash time between coats and allow it to lock up well (a few hours in the hot summer sun would help) Then sand with 400 apply guidecoat and sand again with 600. This will save you a lot of time compared to priming twice. And stepping your grits down from 400 to 600 will take much less time than sanding from an initial cut with both grits-hope this makes sense.

As final prep before color you can give the whole car a good rubdown with a grey scotchbrite-this will mellow any defects left from the blocking process and give the perfect texture for your basecoat, not a necessary operation for sure but it does help and doesn't take very long to do. I usually stack two pads together.

Two coats of base will cover fine, and your plan to look it over for missed sandscratches and nibs etc. is good. Sanding/denibbing between coats with DBC works just fine. But also remember with black even if you do see some very very light hairline scratches through the basecoat these will dissappear once clear is applied-most solid colors won't show these minor defects after clear.

Two smooth. flat coats of clear will be fine, three if you plan to colorsand and buff. Your first coat of clear you want thin but wet and flat, choke the fluid down and bump up the airpressure if needed and move slow if needed. You need to control the gun and paint so don't just pull the trigger and cross your fingers. Use slow activator for hot weather so it stays open longer and gives some flow. Allow that first coat of clear to tack up well then shoot the next coat on a little wetter. Each coat needs to go down smooth or texture will fight you to the end. Check it out after two coats are applied and decide then if any buffing will be needed-if so apply another coat of clear.
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Old 07-06-2007, 06:08 AM
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Do yourself a favor and allow the primer to dry 24 hrs before painting over.
2K primers shrink and rushing it will really exagerate that.
You would be much better off using epoxy in place of the 2k,
let it sit overnight, then sand smooth and paint.
Epoxy gives better protection, adhesion, and less shrinkage.
A paint chemist once told me,
"the worst epoxy is still 10 times better than the best 2k out there"
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Old 07-06-2007, 08:26 AM
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I can't do the Epoxy because of expense vs. worth. I only need a few years out of this and the vehicle will never be shown beyond my son's friends.

The ScotchBrite pads may be a little difficult to come by since the paint store is so far away. I will just have to do the best I can with what I have. I do have some of the grocery store green pads. I'll try them and see how they do.

I failed to mention, and it's of no circumstance other than my own stupidity and learning process, is that I did this roof last week but I mixed the chemicals wrong. I did the tailgate and it turned out beautiful. However, when mixing the chemicals for the roof I used a "slightly" different method. When I did the tailgate I used a measuring cup: 4 oz paint then filled activator to the 5 oz. mark.

When I did the roof I put in 8 oz. paint then 6 tablespoons of activator. DOH!! There are only 2 tablespoons to an oz. I put in 50% more activator than required thus causing the paint to boil from chemically generated heat. The paint curing process is exothermic. The Texas heat didn't help either.

I am going to try to mix it right this time and maybe it won't boil on me. Maybe a ratio of 4:3/4 as opposed to 4:1. Just a little Too much activator in the tailgate paint (I mixed 4:1 as best I coul with the cup) resulted in just a little chemical pop which is the result of too much heat being generated. It looked nice after I sanded them out though then shot clear over it all.

Heat generation from the chemical reaction of the paint/activator mix, along with solidification, causes popping or trapped air bubbles surrounded by solid paint. Look at them through a strong magnifying glass and some will even have a very fine dome on them that can be popped with a sharp needle. The solvents try to escape but the paint hardens and traps the air. The end result is trapped air bubbles or what most call "chemical pop." The mix instructions on the can state from 4:1/2 to 4:1 so I have some leeway.

I will post the results when done. If I screw it all up beyond repair It will go to a body shop and I will just have to write the check.

I can tell you from experience that working with Acrylic Enamel is waaaaaay easier than this stuff. I should have used it instead. Shoulda, coulda, woulda. Does me no good now.

Thanks again to all and especially you baddbob,
Abby.Normal

BTW, after this is over I'm selling all my painting equipment and some of it is pretty nice stuff.
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Old 07-06-2007, 10:45 AM
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Bare metal primer

Do you have any metal prep (phosporic acid). If applied correctly water just sheets off with out rusting. It doesn't seem to go bad so storing the extra is not a problem. Any primer will stick to metal that has been metal prepped . For years this is how it was done, then on nicer jobs came two part self etching primer, epoxies,dtms. I did a 3/4 rear clip on my dads car 16 years ago with metal prep and lacquer primer and enamal top coat. other than faded paint there are no adhesion issues with the paint.

50 girit is overkill, 220 would be fine. 600-800 grit final sand is reccomended for most ureathanes. It is so thin any imperfection shows through it. Get some enamel and dump the stress.
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Old 07-06-2007, 01:30 PM
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50 grit is way not overkill. I have about 8 hours of sanding with a DA and 50 grit and have about 1 sq. ft. left. I had to take a break because I couldn't feel my fingers any longer. Typing this is like typing on something that shocks me with every touch.

I have some singe stage etching primer left over from another small job I did. I'm going to see if it's still usable and shoot it on those bare spots. There really isn't much metal showing considering the square footage of this job. Total, I'd say there may be 10 square inches of bare metal and the rest is OEM primer - and that looks like Epoxy. I will get it blocked today and ready for primer tomorrow. Things are not looking too bad since I realized how stupid I was the first time around. This time it should be a piece of cake.

Go to the bottom of this thread and you will see the last paint job I did. That one took me 6.5 years to complete.
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Old 07-06-2007, 10:50 PM
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Well, etching primer was OK after all those years, sealed in the can. The first coat of Urethane primer went on nice. Especially after I mixed it correctly:
6 oz. primer; 3 tablespoons catalyst, and 2 tablespoons reducer (makes it not cure so fast according to the instructions). I probably should have added another tablespoon of reducer but it's fine. Tomorrow morning I will block and squirt another coat. Progress in the right direction finally.

The 50 grit DA did leave a lot of scratches to fill/block out but I would still be sanding if I used a finer grit. It took nearly 8 hours and a pack and a half of disks. to mention my compressor would not turn off nearly the whole time. My jitterbug sander died today and I had to go get another one. :-(
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Old 07-07-2007, 05:23 PM
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2 coats of Urethane primer on top now. First coat went on a little dry for some reason. I just couldn't figure out the air/fluid mix for the life of me. It went on OK though, I guess. I blocked it with 600 and it covered most of the 50 grit DA swirls. The second coat went on even more dry than the first coat but it went on. It has a lot of dry primer on top. I'm certain it went on wet though. It looked like it went on dry but it really didn't I am going to let it sit for at least 2 hours before I block it for color with 600 wet.

I am really scared the color will also go on dry. I intend on painting some of the masking to see how it flows and to adjust the gun for the proper air/fluid mix.

Gun is set at 50 psi with the trigger pulled. Is that too much/little? I can't seem to get a good wide fan form the spray with decent fluid unless I turn up the air. Then I get too much air and the material dries upon impact.

Suggestions? The gun I'm using is this one:
http://www.tcpglobal.com/proautotool...emNo=MTG+03278

A long time friend of mine offered it to me when I was restoring my 55 Chevy. However, he passed away shortly after and I still have the gun. This guy was in the auto body business for over 50 years. I sure do wish he were here now.
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Old 07-07-2007, 08:45 PM
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Who makes that gun?
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