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Old 04-08-2003, 12:48 AM
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Post going back to bare metal...

G'day everyone.

I've just replaced a few fairly rusty sections of my '74 Holden ute (that's australia's chev el camino, if you've never seen one...), along the rockers and in the wheel arches. I welded in new steel with a MIG, it's not a perfect job but a little bit of filler and no-one will be the wiser.

The car was painted by someone about 5 years ago and the rust was not repaired then, so I'm guessing a lot of the prep work left a bit to be desired, so I'm going back to bare metal for the whole thing.

The problem is that I can't really set aside enough time to completely bare-metal, then prime, the car. And it's fairly humid air, so I wouldn't want to leave anything exposed for long at all. I'm thinking I could strip an area (say a quarter panel), get rid of any rust with a wire brush on an angle grinder, treat it with one of those phosphoric acid solutions, and then prime immediately. Rinse and repeat for each section of car...

Is there anything there that seems wrong?

Also, the car isn't dead straight and will need some filler to look perfect, so I'm wondering if I can apply filler over the top of primer in extremely thin coats? Or does filler need bare metal to stick well?

I've got a bunch more questions but I will spare you the trouble for now... I'll ask them as the need arises.

Thanks for reading.

Col.

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Old 04-08-2003, 01:24 AM
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Its perfectly fine to strip a vehicle section by section. If your sure that the underlying sheet metal has rust I wouldn't worry about any chemical stripper. Just get some 7" scotch brite pads for the angle grinder, or 3M's bristle discs. The scotch brite will both strip the paint and clean the surface rust off in one shot. The 3M bristle discs are better alternative to wire brushes. When using both of these be careful not to overheat the steel.

Small coats of filler can be use over primer just fine as long as the primer has been properly scuffed for adhesion. Have fun! If you have any other questions feel free to ask either here or through PM's or e-mail.

HK
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Old 04-08-2003, 05:38 AM
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Use water-proof primer (primer/sealer?). I worked on a 72 chevy pickup one panel at a time like you are planning to do. It worked out pretty well except for the surface rust appearing through the primer I was using before I got around to paint.
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Old 04-08-2003, 07:13 AM
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Don't use primer/sealer for what you're doing. It is not designed to go over bare metal. Use an automotive epoxy primer (PPG Omni MP 170 or comparable product). It will bond to the metal and after scuffing with 100-180 grit will take bondo very well.

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Old 04-08-2003, 09:19 AM
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"Don't use primer/sealer for what you're doing. It is not designed to go over bare metal. Use an automotive epoxy primer (PPG Omni MP 170 or comparable product). It will bond to the metal and after scuffing with 100-180 grit will take bondo very well. "

Is this a two part product that needs to be sprayed or can it be found in a rattle can?

What then is a primer/sealer for?
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Old 04-08-2003, 09:53 AM
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There are probably other guys who could explain this better but here's my understanding of the difference.

Epoxy primer is a two-part product that needs to be mixed and then sprayed. It is designed to bond to metal (and bondo) and provide good corrosion protection for the surface underneath.

Primer/Sealer is basically designed to seal the primer/body work/OEM finish from the paint that will be going on later. Keeps color from bleeding through and also helps keep incompatible surfaces from reacting against each other. Most modern automotive paints dry by chemical reaction rather than by air, except for some of the cheap enamels, and some brands don't react too well when used with others so the "sealer" part of primer/sealer helps keep this from happening.


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Old 04-08-2003, 12:33 PM
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Epoxy is two part. I dont think it is specifically made to bond to metal better, but it is used because it seals the metal from moisture. The only thing I would recommend in a rattle can is TEC by Martin Seniour Self Etching primer. I have been told it will not work well, but I have used it, and had very good results. I works well for spot repairs and holds up under urethane. It is the only rattle can stuff I would recommend using, but it is not feasable to use it for an entire car. I dont believe it is moisture proof either, but it bonds very well to bare metal if you do a spot repair.

Chris
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Old 04-08-2003, 02:16 PM
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Ideally you are correct. A self etching primer would be the best solution, however since the person who asked the question said he was only going to do one panel at a time I suggested epoxy which is the next best thing. Self etching primer will not hold up to moisture so if you use it and the surface is subjected to moisture over time (rain, high humidy etc.) you will probably have to strip it before you can finish the paint job.

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Old 04-08-2003, 07:01 PM
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Centerline, I was not disagreeing, just answering the rattle can question. I think epoxy is the best thing. I have also heard that urethane primer is good for sealing metal.

Chris
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Old 04-08-2003, 09:03 PM
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So a rattle can self etch primer like Eastwoods wood require a topcoating of epoxy primer before you could safely leave it alone?

(By leaving it alone I mean topcoating it later)
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Old 04-09-2003, 09:05 AM
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[quote]Originally posted by asennad:
<strong>So a rattle can self etch primer like Eastwoods wood require a topcoating of epoxy primer before you could safely leave it alone?

(By leaving it alone I mean topcoating it later)</strong><hr></blockquote>

Yep, but I have never used that stuff so I would not recommend it personally. The Martin Seniour Stuff is made to use with their line of products. Brand X from Eastwood might not hold up to top coating very well. The etching agent may also be questionable.

Chris
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Old 04-09-2003, 09:40 AM
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[quote]Originally posted by TurboS10:
<strong>Centerline, I was not disagreeing, just answering the rattle can question.

Chris</strong><hr></blockquote>

I know. Sorry if my post didn't come across that way though.

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[ April 09, 2003: Message edited by: Centerline ]</p>
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