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Old 01-15-2013, 09:47 AM
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Bare metal finishes

Questions on coating cars in bare metal...Any suggestions on materials to use?

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Old 01-15-2013, 10:26 AM
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2 wet coats of SPI epoxy does the job and prepares the car for follow on painting..

Sam
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I have tried most all of it and now do what is known to work..
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Old 01-15-2013, 12:02 PM
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This is a question that has been bantered about since the creation of the automotive aftermarket refinish systems started. The most important part of any restoration is the preparation of the metal to form a solid foundation that withstand the rigors of all the elements that the top coats are exposed to. It goes without saying that what is underneath your paint is what will allow your finish to stand up over time and what you put down as a foundation will determine the longevity of your finish.

I have used and tried all types of metal preparation materials from vinyl wash to etch to epoxy primers, these products have evolved and are better today than they have ever been. The debate continues, some people claim that an etch primer topped with a 2K primer is the best way to go, others claim that an Epoxy primer topped with a 2K primer will out last any and everything on the market. Many technicians on this site claim that SPI Epoxy over bare metal is hands down the best way to build your substrate to allow for that great finish.

Up until recently I had been an advocate of PPG's DP line of Epoxy primer, top coated with a high quality 2K primer gave me the substrate I required in order to be confident that I was using the absolute best method for my customers. Over the past month I have had an opportunity to use some SPI Epoxy primer over bare metal, before I tried this product, I discussed what I had read on this forum with others in the industry and in one of these discussions an old customer of mine offered to supply me with some SPI Epoxy and let me try it for myself, (He had been been successfully using it for almost 2 years).

The way I started testing the product, as I try and do with any new (to me) product is to abuse it to see how far I can push it. I made several test panels (18" X 18"), roughed them all up with 80 grit with my DA. The first panel I then ground down with a 24 grit disc and applied 2 medium wet to wet coats of Epoxy allowing proper flash times and set aside to cure. The second and third panel I took a ball peen hammer to them, on one panel I applied the Epoxy, did my body work to repair the panel and gave it 2 more coats of Epoxy...on the other panel I did my body work and applied the Epoxy. The filler on both panels was about 3/16 of an inch thick maximum. On the fourth panel I soaked the panel in a salt water solution and allowed it to dry over night, in the morning, wiped the rust off with gun wash and applied the Epoxy...(the reason I did this is because often after a vehicle is stripped it sits around for a few days before it's coated and oxidization can occur without you knowing it), then I baked the panel for 1 1/2 hours at 160 degrees.

I found that the SPI Epoxy had great sanding qualities...it sanded virtually as well as any top quality 2K primer.

The two panels that I prepped, damaged and then repaired, blocked out very well, I then tried to get the filler to let go from the steel by hitting the backside of the panel with a ball peen hammer...they both stood up exceptionally well and the panel that was primed and then body worked held the filler every bit as well as the panel with filler to bare metal.

The panel that was allowed to see rust, minimally cleaned, primed and baked does not appear to have any adhesion issues. I will leave this panel for several more months before I sand it down to see if there is any rust occurring underneath the primer.

The panel that I ground down with 24 grit and primed with 2 medium wet to wet coats of primer blocked out...all grinder marks where filled and I have based and cleared the panel. It has been painted for about 10 days, it has not sank, the clear has not died off and it looks as good as the day I painted it. (I would not do this to a customer's vehicle, I did this to see how far I could push the product and would not recommend this procedure on any vehicle).

The last two panels I will let sit for several months but, I must say, from what I have seen so far I am more than impressed. I feel I can now go from bare metal to primer to block sand to paint. With all of the other Techs that have been glowing about this product and have used it for years, I feel that I too would highly recommend this product.

Oh, and Barry K, if your reading this post, I look forward to trying your base and clear as well...Both of the early Ford's I'm doing will be SPI.

I hope this helps.

Ray
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Old 01-16-2013, 05:48 AM
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I've done a few tests of my own and really pushed the limits of SPI before I was ready to recomend it ...One test was leaving 36 scratches in my filler and using 8 coats of epoxy primer to fill them (it took a whole week to cure) before it could be sanded,the scratches sanded right out never to be seen again its been over five yrs and un painted exposed to the elimates and everything ,no problems at all...
then Barry and I (and a few other pro's) had a disagreement on my use of ospho as a metal prep( he dont like using it) I've been using it for over 30 yrs and wont do a resto without it.so I did two panels ,one bare steel and primed and one treated my way with ospho and then did some adheasion tests with duct tape and using a razor blade cut into the primer to the metal making little 1/4"squares then the duct tape ...then I sanded them both down to the metal to see just how well they feathered...I couldnt find any differences in the two panels both passed every test....However when I cleaned up my yard two yrs later I found that old hood and found the surface of the side I didnt treat was starting to rust where it was previously rusted under the primer and the side I treated was not....Now I'm even more dedicated to the Ospho than ever also SPI epoxy.my two favorite products ever...
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Old 01-16-2013, 06:16 AM
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The best part about using epoxy primer is that you are coating the bare metal with a moisture barrier. You can also put bondo over it and have a good base with no bare metal for rust to start.
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Old 01-16-2013, 06:17 AM
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Originally Posted by deadbodyman View Post
I've done a few tests of my own and really pushed the limits of SPI before I was ready to recomend it ...One test was leaving 36 scratches in my filler and using 8 coats of epoxy primer to fill them (it took a whole week to cure) before it could be sanded,the scratches sanded right out never to be seen again its been over five yrs and un painted exposed to the elimates and everything ,no problems at all...
then Barry and I (and a few other pro's) had a disagreement on my use of ospho as a metal prep( he dont like using it) I've been using it for over 30 yrs and wont do a resto without it.so I did two panels ,one bare steel and primed and one treated my way with ospho and then did some adheasion tests with duct tape and using a razor blade cut into the primer to the metal making little 1/4"squares then the duct tape ...then I sanded them both down to the metal to see just how well they feathered...I couldnt find any differences in the two panels both passed every test....However when I cleaned up my yard two yrs later I found that old hood and found the surface of the side I didnt treat was starting to rust where it was previously rusted under the primer and the side I treated was not....Now I'm even more dedicated to the Ospho than ever also SPI epoxy.my two favorite products ever...
Thanks Mike, you answered my question from another thread....I couldn't figure out why it took you 8 coats of primer to fill 36 grit scratches and it only took me 2 coats to fill 24 grit scratches that had been lightly DA'ed with 80 grit....I didn't realize that your 36 grit scratches where on filler, leaving a deeper foot print than 24 grit on steel...that coupled with the fact that I, for all intense and purposes, pounded my primer and you probably applied it correctly.

It's good to hear that you found your hood and you have a test that is 5 years in the making....my test is only 3 weeks to a month old and I fully expect the panel with the 24 grit scratches to sink...how much remains to be seen.

I've never tried OSPHO but I think I should give it a try as well.

Thanks for the clarification Mike...I was somewhat confused for a while there.

Ray
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Old 01-16-2013, 07:47 AM
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Good information guys. As I have mentioned on another thread I am repairing 2 doors with bare metal adhesion issues (bubbles)after 5 years. They were epoxied with PPG DPLF on bare steel after using RustMort. The metal is very shiney and appears to have needed to be sanded better with 80 grit and/or the acid neutralized better. It is odd that they held up well for 3 or 4 years and started to fail badly in the last year.

The tests you guys have done and the follow up information is very much appreciated.

John L
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Old 01-16-2013, 08:10 AM
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Originally Posted by John long View Post
Good information guys. As I have mentioned on another thread I am repairing 2 doors with bare metal adhesion issues (bubbles)after 5 years. They were epoxied with PPG DPLF on bare steel after using RustMort. The metal is very shiney and appears to have needed to be sanded better with 80 grit and/or the acid neutralized better. It is odd that they held up well for 3 or 4 years and started to fail badly in the last year.

The tests you guys have done and the follow up information is very much appreciated.

John L
Yes John, one of the joys of having been in a position to rep products for different manufacturer's is that when a new product came out, we got to run it through it's paces and try and push it to the ultimate limits...I think I learned more by doing this than studying the tech sheets because anytime a shop had a failure with regards to product, they did it by the book every time...LOL... and you wouldn't believe how often I saw "product failure" up and above any torture test I could have thought of. If I knew how far a product would go without failing, it gave me a better idea of how badly some products had been abused. It also gave me an indication of the versatility of a product.

The fact that you didn't notice a problem until 5 years after the vehicle had been painted, considering the product that was used (rustmort) and the adhesion issue being in part mechanical (metal to shiny) speaks volumes for Epoxy primer.

Before I tried SPI Epoxy I made sure I kept an open mind. So far I am impressed and look forward to trying the base coat and clear.

Ray
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Old 01-16-2013, 08:26 AM
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SPI epoxy. Is by far the best I ever used... Mr.Barry is also by far the best to talk to.... I highly recommend SPI Primer...
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Old 01-17-2013, 06:21 AM
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John ,I imagine you keep that car inside and totally clean only driving it on weekends and such...I think the sun has a lot to do with that bubbling and would have shown up much earlier if it was kept outside or was a DD..
.its definately an adheasion problem and most likely caused from the rust mort whether its the product itself or (god forbid) user error is the question...but being that its in the reveil tends to make me think there was some excess left in there that was missed from sanding.
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Old 01-17-2013, 08:24 AM
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Quote:
Originally Posted by deadbodyman View Post
John ,I imagine you keep that car inside and totally clean only driving it on weekends and such...I think the sun has a lot to do with that bubbling and would have shown up much earlier if it was kept outside or was a DD..
.its definately an adheasion problem and most likely caused from the rust mort whether its the product itself or (god forbid) user error is the question...but being that its in the reveil tends to make me think there was some excess left in there that was missed from sanding.
I tend to think this my fault. I posted pictures on the PPG Deltron epoxy thread. Take a look and see what you think. I personally think it may be a 2 fold problem. Metal needs more tooth and acid needs to be neutralized.

John L
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