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Old 11-21-2017, 04:46 PM
Mr fixit Mr fixit is offline
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Default Car metal primer question

Hi Group,

I know this is a metal forum but I'm not sure of other places to ask my question. Recommendations welcomed.

I have a ongoing, since 2000 (family life stalled it ) car project that I had media blasted 5+ yrs ago and primed with NAPA Crossfire Primer surfacer on bare metal. This was before I read that I should have used a different primer first.

I'm working on the metal repairs now and have read that a Epoxy primer is the way to go.

So the question is, have I shot my self in the foot by using the wrong product, or can I move forward with the correct products that you might suggest to complete the project.
I'm hoping to have it repaired and prepped for paint by the first of the year if all goes as planned.

I look forward to any and all suggestions on what my next moves should be. This will be my first restoration.


TX
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Old 11-21-2017, 09:53 PM
crystallographic crystallographic is offline
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Quote:
Originally Posted by Mr fixit View Post
Hi Group,

I know this is a metal forum but I'm not sure of other places to ask my question. Recommendations welcomed.

I have a ongoing, since 2000 (family life stalled it ) car project that I had media blasted 5+ yrs ago and primed with NAPA Crossfire Primer surfacer on bare metal. This was before I read that I should have used a different primer first.

I'm working on the metal repairs now and have read that a Epoxy primer is the way to go.

So the question is, have I shot my self in the foot by using the wrong product, or can I move forward with the correct products that you might suggest to complete the project.
I'm hoping to have it repaired and prepped for paint by the first of the year if all goes as planned.

I look forward to any and all suggestions on what my next moves should be. This will be my first restoration.


TX
(Warning: primer/surfacers are porous and allow moisture to absorb down to the metal.)
Otherwise you are ready to sand ...
Tough call, at this point.
Might want to sand down and re-coat with a good base. ....
Or just leave it and go from here.
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Old 11-22-2017, 07:07 AM
shorty shorty is offline
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If you handed me this job to complete I would want to remove your primer and recoat just to be sure I have I known good substrate for the reason Kent mentioned.
P.S. you get what you pay for with 2 pack primer/fillers so don't cheap out on that.
Pat
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Old 11-22-2017, 01:06 PM
Mr fixit Mr fixit is offline
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Hi Guys,

I appreciate the responses. I did not know the primer I used was porous, sounds like for me to get a good finished project, I better rermove the primer as much as possible and start with the correct base primer.

TX
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Old 11-23-2017, 02:04 AM
shorty shorty is offline
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All primer/fillers are porous, i've been told by paint chemists that it's a drawback of it being able to go over a variety of surfaces e.g steel ,lead ,brass and a million different types of body filler and they wont bother changing it because it's not top coat,they recommend never leave a primed car out in the weather or under a plastic cover for to long (they sweat solvent) and to top coat with in six months.
If I'm on a long resto job I put a couple of coats of acrylic primer as I complete a panel to stop surface rust on it ,when the repairs have all been completed it gets a rub with 240grit dry paper, rolled in the booth and given it's proper prime/fill,two weeks later it will have paint on it.
Lots of logistics involved when you need to make money out of it.
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Old 11-23-2017, 11:20 PM
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Jack 1957 Jack 1957 is offline
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I preface this with my credentials: I have over 30 years collision and refinish experience most of which was at a BMW and Lincoln dealership. I am an ASE Certified Master Collision Tech and ICAR Gold Refinish Tech. I mention this because, no doubt, you will get various conflicting replies which will probably leave you more confused than you may have been prior to asking.

There are two potential problems you could be facing. First, you didn't mention whether the primer you used was a 2K or single stage lacquer. If it was not a 2K get it off of there. All of it. It will fail. If it was a quality 2K primer you may be OK but do you want to risk a paint job on it?
I used to apply 2K primer filler directly to bare steel over repairs and never had any problems with delamination, feather breakage, or shrink. BUT! I was generally painting the next day or within a couple days. The shop was temperature controlled 24/7. There was very little chance of moisture saturating the primer, which leads to potential problem #2;

There is a lot of talc in primer surfacers and primer fillers. The talc builds coating thickness and also helps make sanding easier by keeping the primer from clogging the abrasive. On the downside, the talc also makes the dried primer porous. Over time it can absorb moisture and allow it to wick all the way to the substrate. Over the years that your project has been setting, it's possible that enough moisture has come in contact with the underlying steel to cause some surface rusting.
I know this is not what you want to hear but I would strip the primer and apply a quality epoxy primer. It has superior adhesion. Do not bake or force dry, even if the label says you can. Epoxy primers are a derivative of catalyzed enamel. They will stay "wet" for an hour or more depending on temperature and humidity. This is what you want! it gives the coating time to bite. You now have the best starting point for anything further that you'll be doing.
Urethane paint systems are insanely expensive. I promise you, if you shortcut anything prior to laying down the paint, you will regret it.
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Old 11-24-2017, 12:39 AM
Mr fixit Mr fixit is offline
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Wow Jack,

I had to read your post a couple of times to get the point. It sounds like I have shot myself in the foot (wrong application not the product) by using a 2K Acrylic Urethane primer surfacer by NAPA called Crossfire a Martin Senour Paint product.

I'm looking at stripping the outside of the car as much as possible, but the inside of the doors, dash, and frame work around the glass and doors I'm thinking of leaving as is. Is this a mistake?
Being the outside is the largest areas and the part that would have the greatest impact with a failure long term, is my theory. I do realize moisture has not been selective in getting through to the metal, but this is a daily driver when I'm done and not completely stock, so maybe I can slide a little.

What do you think? I know I have some work ahead of me either way, just would like to save the time of redoing these particular areas if possible.

TX
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Old 11-24-2017, 10:12 AM
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Steve Hamilton Steve Hamilton is offline
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I would agree with above. Good advice to strip it all off!
If you are on a very tight budget then,I would say do a little testing. Use some chemical stripper in random areas and see what the metal looks like under the primer. Apply with a brush, let stand until bubbled up, wipe off with rag or toweling. Clean up with lacquer thinner. Don' t use steel wool or scotch bride as it will scratch off any evidence of corrosion. Check closely along edges and convex creases as the surface tension of the liquid primer pulls it away from those areas and leaves a thinner film build. Thinner coat usually means less corrosion protection.

I would not sand it off as that would remove any small amounts of rust as it removes the primer.

If the metal is still clean. Under the primer, Then you might gamble and block sand it. Prime it with epoxy to seal it and proceed with filler work or high build as normal.
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Last edited by Steve Hamilton; 11-24-2017 at 10:29 AM.
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Old 11-24-2017, 12:54 PM
Mr fixit Mr fixit is offline
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Hey Steve,


That is a great suggestion of using the stripper to investigate the condition under the existing primer. I appreciate the thinking outside of the box on this.

The car has been stored indoors the whole time and in Oregon our humidity is on the low side most of the time, unless it's 100% rain, which we do get.

I tended to lay it on heavy vs light being new to shooting paint from a gun vs a rattle can.

I'm going to give this a try, maybe I can save my time if it checks out OK.
Will update when I get some paint stripper and do the deed.

TX
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Old 11-24-2017, 01:11 PM
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Kerry Pinkerton Kerry Pinkerton is offline
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What about soda blasting it all off? Wouldn't that be the least destructive way to remove the old primer?
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