As the title says I have sanded the roof till the SMC, I have used 80 grid and after 150 dry sand paper. I has careless and the 80 grid leave some marks to the surface. What is the correct procedure in order do it right and don’t have any problems in the future? Is epoxy primer ok or I need something else first? And if the scratches are still visible after primer what should I do?
I had to do this because the original paint was peeling off.




Also I have some small spots to the door panels were the plastic show up but very small areas.

The same to the front bumper, also it has a small tear about 1,5 inches that I glassed it. I also want to cover some screw holes, will fiberglass be ok or I will need something special for the urethane bumper?

I went to a paint shop this morning who sells PPG paints and the employ couldn’t find anything for the SMC and asked for me to tell him what the factory procedure for painting is… So I want to be 100% sure…

Thanks in advance, I searched and looked other topics related to painting but I am not 100% sure and I am looking a professional advice.

[This message has been edited by Chris_86GT (edited 08-31-2009).]

I would hit it with a coat or two of self etching primer then do it with some primer/filler for the scratches left from the paper.
Build it up enough to fill the scratches and to feather it into your blunt edges of factory paint.

[This message has been edited by Indiana_resto_guy (edited 08-31-2009).]

There are two ways to go at the scratches. The first way is to use some SMC Panel Adhesive and do a skim coat and re-sand. That is likely the better way in terms of good surface integrity. The second way is to use Auto Glaze (also known as green stuff) and apply it directly on the SMC. It will work also. I don't think I'd prime at this point, I'd make sure that surface was as good as I could get it. The problem with priming early is that you end up sanding off a lot of primer which is, in my book, a waste.

Good luck with it

Arn

Thanks for the replies,

So I will not have any problem using the epoxy primer directly to the SMC panels or Bumper. My only problem will be the scratches, they aren’t too deep but I will know better after I prime it. In Greece we don’t have many cars with SMC panels and the employees can’t help you because they are unfamiliar with this.

Is the Marine Tex good for covering scratches?

DO NOT try to fill simple scratches with any kind of glaze or filler!
You're on the right track. PPG epoxy is the BEST thing to use on all your panels. Get the 401 catalyst (you'll have an induction period to wiat for) as it's more flexible for the bumper covers. If the scratches are deep, you might need to prime over the epoxy with a catalyst-hardened hi-build primer, but from your description I doubt you'll need that. Probably two full coats of epoxy will do it. Give it several days to cure, then sand it smooth with 400 wet & paint. Use a "guide coat" (just fog a little flat-black spray paint) before sanding to make sure all the scratches & imperfections are gone.
EDIT: you need to gat a product specificly for RIM to repaiur the bumper - grind that fiberglass back off of it. Do a search for RIM or bumper repair & my username for instructions on how to do repairs.
I've been doing this for nearly 40 years....
~ Paul
aka "Tha Driver"

Which do you most can't the least?
What I most can't the least, would be do not a bad job but always a good.

[This message has been edited by Tha Driver (edited 08-31-2009).]

I realize epoxy is a good product, however, the panel is SMC. You therefore are best advised to use an SMC product. It bonds better than epoxy. The other issue about auto glaze is that PROFESSIONAL CUSTOM shops use auto glaze to finish off panels.

Epoxy is generally not used for the finish prep except where you have it ready for the first primer coat.

Using epoxy over imperfections will simply create more sanding. I've been there and done that.

Arn

quote Originally posted by Arns85GT: I realize epoxy is a good product, however, the panel is SMC. You therefore are best advised to use an SMC product. It bonds better than epoxy. The other issue about auto glaze is that PROFESSIONAL CUSTOM shops use auto glaze to finish off panels. Epoxy is generally not used for the finish prep except where you have it ready for the first primer coat. Using epoxy over imperfections will simply create more sanding. I've been there and done that. Arn

Epoxy primer will stick as well as anything, & better than most everything. To go through the task of wiping filler on scratches that are not as deep as 80 grit is a complete waste of time. With any primer they will simply sand smooth & you can then paint. If you have imperfections deeper than that, PPG epoxy is the perfect substrate over which to wipe most any kind of catalyst-hardened filler/putty. (I don't use anything that's not catalyst hardened.) Then you can spot in with more epoxy & sand & shoot. In fact, I've painted over 180 dry scratches with a single coat of epoxy & then painting without sanding the primer at all.
~ Paul
aka "Tha Driver"

Any society that would give up a little liberty to gain a little security will deserve neither and lose both. - Benjamin Franklin

If you work on GM non-metal body parts, like Corvette, or Fiero, you will know that unlike metal body parts, you don't necessarily use epoxy primer although you can do so if you want to spend the extra. You don't need to. It's plastic. In fact, after doing mod work on my car, I can tell you that SMC Panel Adhesive is pretty much the only thing to use to fill imperfections. Auto glaze just finishes off the finer stuff.

I've tried a heavy primer and it just created work. SMC is a different animal to metal. I fail to understand why you would use expensive primer which you have to sand almost completely off to cover scratches that a little glaze or panel adhesive would smooth out before you go to spray.

But if that is the system you use, by all means that is your prerogative.

Arn

I've been working with SMC (Corvette repair/customizing) since it first came out. What I'm saying, is there is no need for filler for light scratches. Using filler for that is just extra work. Yes, if you have gouges, chips, cracks, etc. you should grind them with 24 grit & fill them with SMC filler.
Re-read the original post. He's talking about large areas that he's sanded with 80 grit & then 150. No reason to wipe all that with filler & have to sand & block that out.
~ Paul
aka "Tha Driver"

I have taken some better and closer pics of the sunroof panel and bumper, I will post them when I will go back home so you will have a better look of what I need to do.

Thanks for your replies, Chris

quote Originally posted by Chris_86GT: I searched for SEM products and found this. http://semproducts.com/imag...ing%20Procedures.pdf At the second page the 39927 FLEXIBLE SEM WELD seems to be the perfect for the bumper holes and the small 2ince tear. And for the scratches on the SMC surface at the 4th page 39542 CARBO-FILL or 39492 NO SWELL PLASTIC PANEL FILLER Can someone verify that this are the correct products, so I can try to find something similar here in Greece?

I use SEM 39708 Flexible SEM-Weld. I guess you haven't done the search I suggested above...
Not familar with the other products.

I did searched and find some other posts but maybe I didn’t notice the part number, 4-5 post open at the same time must disoriented me.
Thanks for the part number Tha Driver!

You can see at the pic were the tear is; so the SEM 39708 Flexible SEM-Weld will be ok for this and the small holes?

------------------------------------------------EDIT------------------------------------------------------
SEM 39708 and SEM 39927 are for the same thing and according to this document they will do the job. Now I have to find something similar here in Greece or just order from the internet… :-)
http://semaerospace.com/ima.../1/TDS/FSW%20TDS.pdf
------------------------------------------------EDIT------------------------------------------------------



And a closer pic of the scratches, I forgot to check if they can caught your finger nail in order you to know how deep they are. I will do it when I get back home.

[This message has been edited by Chris_86GT (edited 09-02-2009).]

quote Originally posted by Chris_86GT: I did searched and find some other posts but maybe I didn’t notice the part number, 4-5 post open at the same time must disoriented me. Thanks for the part number Tha Driver! You can see at the pic were the tear is; so the SEM 39708 Flexible SEM-Weld will be ok for this and the small holes?

What you'll want to do (after you're removed the fiberglass), is grind the back of the tear with a 24 grit disc - SLOWLY so as not to heat up & melt the material. Heating it will cause the pores to close & nothing will stick. Chop up some fiberglass mat with scissors and mix it in the SEM. Then mix the catalyst & put a good coat on the back (at least 1/8" thick). Once that sets up, grind the front of the tear into a "V", & fill that with the SEM. Chopped mat is not critical here, but dosen't hurt. The tiny holes can be simply V'ed out & filled with the SEM.
Hard to see scratches in a photo...
~ Paul
aka "Tha Driver"

quote Originally posted by Tha Driver: What you'll want to do (after you're removed the fiberglass), is grind the back of the tear with a 24 grit disc - SLOWLY so as not to heat up & melt the material. Heating it will cause the pores to close & nothing will stick. Chop up some fiberglass mat with scissors and mix it in the SEM. Then mix the catalyst & put a good coat on the back (at least 1/8" thick). Once that sets up, grind the front of the tear into a "V", & fill that with the SEM. Chopped mat is not critical here, but dosen't hurt. The tiny holes can be simply V'ed out & filled with the SEM. Hard to see scratches in a photo... ~ Paul aka "Tha Driver"

Thanks!!

I will try the 'Finger nail test' if this do any help.

also, where you are "transitioning" from bare plastic to paint, EACH layer (color) of paint Should be feathered back 1 inch, Then primed. Otherwise, once you get a shine on it, it will look like a "Cliff".

quote Originally posted by Lou6t4gto: also, where you are "transitioning" from bare plastic to paint, EACH layer (color) of paint Should be feathered back 1 inch, Then primed. Otherwise, once you get a shine on it, it will look like a "Cliff".

I haven’t finished sanding but I didn’t know for the 1 inch feathered back for each layer.
Thanks for the tip!

quote Originally posted by Chris_86GT: I checked the scratches and they can’t catch my finger nail, only a slight resistance. I know that the epoxy primer is thin but if I am lucky with two layers it will be ok.

PPG epoxy primer is not that thin. Two coats, allow to dry for several days, sand with 400 wet & paint.
EDIT: On the feathering, just get it smooth (may not need a full inch). When sanding the primer, use a sponge pad or paint paddle (on flat surfaces) to wrap the sandpaper around. Using a guide coat like I mentioned above, you'll be able to see when the scratches are gone, & the feathering & the primer are smooth.

quote Originally posted by Chris_86GT: I did a small repair using fiberglass on the hood; is SMC compatible or I have to remove it?

Fiberglass Evercoat Vette Panel Adhesive part # 870. Again, mix some chopped mat to give it strength.
~ Paul
aka "Tha Driver"

[This message has been edited by Tha Driver (edited 09-02-2009).]

quote Originally posted by Tha Driver: Fiberglass Evercoat Vette Panel Adhesive part # 870. Again, mix some chopped mat to give it strength. ~ Paul aka "Tha Driver"

Thanks Tha Driver,

And a + for your patience and help.

quote Originally posted by Chris_86GT: I am a little bit confused with the Evercoat Vette Panel Adhesive. Since its polyester body filler and I used polyester resin with fibreglass mat what is the differences between them?

The Vette panel adhesive is made for SMC. SMC has a release agent in it to pop the parts of the mold. When they first came out with it we don't know it was different, & we used resin & mat just like always. Soon found out it was not a permanent solution. Just dosen't stick as well as it did to the older 'Vette panels.
~ Paul
aka "Tha Driver"

[This message has been edited by Tha Driver (edited 09-03-2009).]

quote Originally posted by Tha Driver: The Vette panel adhesive is made for SMC. SMC has a release agent in it to pop the parts of the mold. When they first came out with it we don't know it was different, & we used resin & mat just like always. Soon found out it was not a permanent solution. Just dosen't stick as well as it did to the older 'Vette panels. ~ Paul aka "Tha Driver"

Ok, Thanks!

I also did some small repairs using vinyl ester resin, (I didn’t use polyester resin for all of my repairs) I don’t know if this does mater for my previous repairs. Is it ok or I am on the wrong way again?

Door panel


Wing stands

The door skin is RRIM; use the same SEM product as for the bumper covers.
The Spoiler is some type of plastic (can't remember offhand which type). Probably spme type of two-part epoxy would be best, but you may can use the same SEM shtuff. Look on the instruction sheet to see what all it covers. Also, if it's any kind of crack, mix in a little chopped mat again & re-inforce the back.
~ Paul
aka "Tha Driver"

The earth is in much more danger from human action, then from natural disastors. - Steven Hawking.

I did all the repairs the same day; I didn’t post all of my repairs because I thought that it was ok. Anyway, better late than never.
On Monday I will go to the shop to see what I will find, SMC is extremely rare in Greece…

[This message has been edited by Chris_86GT (edited 09-07-2009).]

I have checked for the Sem flexible weld and the Evercoat Vette Panel Adhesive but with no luck, they couldn’t suggest me something similar. So I will order from the internet.

For the PPG epoxy primer they gave me two different codes the D8095 Epoxy Primer Filer and the DP4000 2k Primer. Which one should I use?

Also suggested me the MaxMayer Duralit filer Rapido; does anyone knows about it?

Thanks, Chris

I use the DP50LF, with DP401LF catalyst. Read the instructions - there is an induction period. You use the 401 if you're shooting flexible panels, but it works fine on everything else too.
EDIT: never heard of the MaxMayer Duralit filer Rapido.
~ Paul
aka "Tha Driver"

[This message has been edited by Tha Driver (edited 09-08-2009).]

An update of the repairs

I sprayed one mist coat and two wet coats of epoxy primer. The primer was a little bit thick (I didn’t used too much thinner) so it filled up the marks from sanding very well. Fist sprayed only the area with the problem, sanded and after sprayed the entire roof.


For the bumper I used the 39927 Flexible SEM-Weld.

Whatever primer you choose to use, there all for basicly same thing. Their job is to give you a uniform surface to paint, filling any imperfections like sanding scratches. Once you sand the primer and get all the scratches, pinholes or whatever out, you reprimer any spots you sand thru. When the entire repair is sanded and you see nothing in the surface and its totally covered with primer, it ready for paint. I usually finish a repair with #80 myself, then sometimes #180 surronding paint, followed by primer/ surfacer. Soon as its sanded with #360/400, its painted. You dont want to sand with anything finer than that to paint unless you doing a spot repair. You may have adhesion problems of the basecoat to the primer with something finer. I have to be particularly careful of this because I do a lot of 2 tone, multi tone and graphics paint jobs. I dont want the colors coming up with masking tape before their cleared.

quote Originally posted by rogergarrison: Whatever primer you choose to use, there all for basicly same thing. Their job is to give you a uniform surface to paint, filling any imperfections like sanding scratches. Once you sand the primer and get all the scratches, pinholes or whatever out, you reprimer any spots you sand thru. When the entire repair is sanded and you see nothing in the surface and its totally covered with primer, it ready for paint. I usually finish a repair with #80 myself, then sometimes #180 surronding paint, followed by primer/ surfacer. Soon as its sanded with #360/400, its painted. You dont want to sand with anything finer than that to paint unless you doing a spot repair. You may have adhesion problems of the basecoat to the primer with something finer. I have to be particularly careful of this because I do a lot of 2 tone, multi tone and graphics paint jobs. I dont want the colors coming up with masking tape before their cleared.

I am going to paint the car red; I have bought the DuPont Ferrari red (acrylic, base and clear). A friend of mine has working in a body shop when he was younger and told me that the base coat is very thin and don’t covers sanding scratches even from a 800 wet sand paper. They where sanding with 1200-1500 sand paper before base. Also for red and blue (non metallic) they sprayed a layer of white in order to cover any body work on primer that will appear like a shadow on the final base.

This confuses me a little; from the shop I bought the paint they gave me 800 wet sand papers.

quote Originally posted by Chris_86GT: I am going to paint the car red; I have bought the DuPont Ferrari red (acrylic, base and clear). A friend of mine has working in a body shop when he was younger and told me that the base coat is very thin and don’t covers sanding scratches even from a 800 wet sand paper. They where sanding with 1200-1500 sand paper before base. Also for red and blue (non metallic) they sprayed a layer of white in order to cover any body work on primer that will appear like a shadow on the final base. This confuses me a little; from the shop I bought the paint they gave me 800 wet sand papers.

I never sand with anything finer than 400 wet before base coat. Anything finer than that reduces adhesion, although I might add that I use PPG epoxy primer (the DP50LF) as a sealer before painting & you can paint over that without sanding if you like (& have a smooth surface). Sealing with the DP will eliminate the "shadow" effect you're referring to.
Two coats of base should cover in most cases, unless it has a lot of transparent color in it. In that case, it may take up to 4 or in some extreme cases 5 coats. If the Ferrari red you're using is the factory color for the 308s, it IS a transparent color & will need about 4 coats.
So you can final sand the body with 180 dry or 320 wet, shoot a thin coat of the DP primer, & 20 minutes later shoot the base &
then clear. If the body is not quite smooth, you can final prime with the DP & wet sand with 400 then paint.
HTH,
~ Paul
aka "Tha Driver"

Pardon my driving; I'm reloading.

It used to be common to sand primer smooth with 600/800. That was generally done for laquer finishes. Laquer will burn into just about any surface except bare metal. Laquer paint was very thin sometimes up to 400%, and took a minimum of 5 or 6 coats of color. Newer paint like basecoat/ clearcoats are 'high solids' which means there is a high content of pigment with very little clear carrier in the mix. They are 3 or 4 times as thick and 90% of colors fully cover in 2 coats. Its then protected and given a gloss by the clearcoat. 400 scratches are easily covered with 2 coats of base and 2-3 coats of clear. Never put more clear on than that. IF you are going to do a LOT of color sanding and buffing, you could possibly go up to a maximum of 4 clear coats since your likely to sand and buff off 2 of them. More makes it very succeptable to chip or crack especially if exposed to hot sun.



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[This message has been edited by rogergarrison (edited 01-13-2010).]

I have also found that 2 coats of base are good. I do this with Nason or Duplicolor (lacquer).

I also got into trouble using more than 2 coats of clear. The cure time went up significantly.

Arn

quote Originally posted by rogergarrison: It used to be common to sand primer smooth with 600/800. That was generally done for laquer finishes.

That was done 'cause laquer primer will soften when you spray paint (which has solvent) over it. Anything like 400 or heaver & it swells enough to see the scratches. I always used 600 wet when I shot laquer (back in the day - 30 years ago).
~ Paul
aka "Tha Driver"

Don't be late - in the wrong direction...

I shoot lacquer with 400 generally. However, it can be done with 220 if necessary. If you get down to it, lacquer can go on your regular primer without sanding at all. I find that 400 is optimum. 600 is just too fine. But, that is kind of subjective.

It is much more critical with a urethane.

Arn

Yesterday I was at my mechanics place and his painter came to take a car for paint. We talk a little on how to prepare the car for base color; he told me to sand very light with 1000 grit then spray a mist coat of base and a wet after. Let it dry, wet sand with 2000 and spray two thin wet coats of base. I am using a two stage acrylic. It seems that everybody was his own system that works. This is close to what my friend told me to sand with 1200- 1500; doing this I will avoid spraying two times the base.

I don’t know how you do it not showing the scratches on the base color with 400 grit; the only logical explanation is that you use different paints from that we have in Europe?

quote Originally posted by Chris_86GT: Yesterday I was at my mechanics place and his painter came to take a car for paint. We talk a little on how to prepare the car for base color; he told me to sand very light with 1000 grit then spray a mist coat of base and a wet after. Let it dry, wet sand with 2000 and spray two thin wet coats of base. I am using a two stage acrylic. It seems that everybody was his own system that works. This is close to what my friend told me to sand with 1200- 1500; doing this I will avoid spraying two times the base. I don’t know how you do it not showing the scratches on the base color with 400 grit; the only logical explanation is that you use different paints from that we have in Europe?

I use a lot of Sikkens; guess where that's from?
Your painter is way off base (no pun intended). There is no need to sand the base coat, unless you have a problem such as dirt or runs (it's next to impossible to get runs in base, but it does happen).
What you really need to do is get the tech sheet for the paint you're using, & go by that. Any good paint store can provide you with the tech sheets for the paint they sell.
Part of the not showing 400 scratches is the fact that I'm using the PPG epoxy primer, which is harder to sand than the laquer primer that *some* folks use (& other primers as well). But I can't imagine any paint being too thin to shoot over 400 wet & showing scratches after 2 or 3 coats.
~ Paul
aka "Tha Driver"

Hey old man, have you lived here all your life?
"Nope - not yet."

I also NEVER sand on bare basecoat except to fix a flaw and then you still have to dust on some basecolor to that area. If you sand basecolor right before clearing a metallic color you will 'streak' the metallic particals on the surface. It will be very obvious after you polish the finished job and no way to fix it other than total repaint.