Primer, Sealer and paint options suggestions
- Thread starter 59-600
- Start date
dnudelman
True Classic
myredracer
True Classic
OMG, it's complicated!! I can tell you lots after having done a bare metal up restoration on my 600 body all the way to doing the paint at home. I spent hours and hours, days and days and weeks and weeks scouring the internet trying to figure it all out.
Briefly:
If stripping to bare metal whether it's media blasting or using sanding/stripping discs, you've got to get primer on the bare metal pretty much immediately otherwise "flash" rusting occurs. You can't see it at first, but it's there and will ruin a paint job. Most people use epoxy primer on bare metal. It provides the best adherence and durability. Then you can use "high build" urethane primer over the epoxy. It sands easily and is excellent for smoothing out imperfections and high and low spots. The procedure is called "blocking" because you use sticky-back sandpaper on semi-hard rubber blocks (which come in various sizes and shapes).
Some folks put down the high-build primer first followed by epoxy, but I don't know why that would be better. Both are called "DTM" which stands for "down to metal". Epoxy primer is not easy to sand compared to the urethane primer. Once you have primer on, there is a window of only days to apply subsequent coats, whether it's more primer or the final topcoat. Reason is, the subsequent coats will chemically bond together otherwise you MUST sand down the primer to get a mechanical bond. Different brands of paints have different window periods and IIRC, SPI has the longest at 7 days. I used Nason primer which has a 2 day window so you have to work faster. If you're past the window, you need to scuff epoxy primer with sandpaper or scotchbrite pads. Hard to do in some places like underneath where there's lots of overlapping seams, nooks & crannies and hard to reach places.
Don't make the mistake of taking a body somewhere to get the entire thing media blasted and then think you can leave it bare and take months to work on repairs and mods and then spray primer on it. You can always remove primer from areas you want to work on. You can get a spot blaster or a pot blaster like the 40 lb one HF has. If wanting to media blast a body yourself, coal slag is a good media. Tractor Supply has some they call Black Diamond. Use the fine grit stuff. It's messy and it goes everywhere so you want to put up some temporary sheeting to contain it. You can scoop/sweep it up and screen it and put it back in the pot blaster. It's slow doing it yourself but works very well.
Primer can be applied over pre-existing paint in most cases if it's in good shape. Back in the 50s, Fiat used some kind of enamel over what I think was a red oxide primer (or similar). Technology has changed a lot but as long as the old paint and primer is in good shape, I think you should be okay to leave it on and just strip away what doesn't seem okay. The roof for example might be something that can be left on, but for the small area it is, you are probably better to strip it all off. Might even find bad spots under anyway. It might be a good idea to strip all paint and primer out of seams. Fiat used a lot of a type of putty on some seams and I would remove that if planning to paint over it.
Before spraying primer and subsequent coats of primer and paint, make sure to use wax and grease remover along with tack-free cloths.
Forget about using phosphoric acid metal prep products. Not needed and in some cases it's not compatible with primer and paint and can cause failures. Needs to be properly neutralized too. Best thing is strip to bare metal and get the primer on pdq.
One excellent filler is called All-metal. It can be applied over bare metal which really helps. The bare metal has to be super clean. The spray the primer over that. The All-metal doesn't have to be sanded out 100% perfect but need to sand down high spots. Once primer is on, then you use plastic filler (aka bondo) over any remaining imperfections. Seam sealer should be used over seams, joints and cracks.
There are various grits of sandpaper that should be used. More aggressive grits like 60 can be used on bare metal and first application of filler on bare metal. Then you work your way up to smaller grit paper to remove scratches. If using single stage urethane, you can stop at 320 grit. If using a base coat and clear coat, you'll need finer grit otherwise you'll see sanding scratches underneath.
If you are doing welding on any sheet metal, you'll want an angle die grinder and roloc discs. These are available in as small as 3/4" dia. up to 3" for larger areas.
If you're thinking of painting at home, single stage urethane works well. Doesn't need special equipment or paint booth. NOTE WELL that urethane primer and urethane topcoat paint is highly toxic because it contains isocyanate. You can't spray it indoors unless you have a supplied-air respirator setup (expensive). You can use it outdoors with a fullface respirator and the correct cartridges and are fully suited up because the isocyanate can be absorbed through skin. Urethane paint hardens quite fast and is even hard enough the following day to sand if needed.
If you have runs on the urethane paint or too much "orange peel" , it can be wet sanded with 600 grit paper ending up with 3,000 or finer. After that, 3M makes some excellent rubbing and polishing compounds.
The enamel that was used in the 50s wasn't high gloss and if you want your car to look more like it originally was, a base coat followed with a clear coat will look a LOT glossier and some may not be happy with it. There are flatteners that can be added to paint but they apparently are hard to get to work well.
If you are doing a restoration to bare metal over a long period of time, you kinda need to plan things out. You might for example, focus on the underside of the car first and get it primered and maybe rubberized undercoat over that is paintable (or leave it black). Then maybe do sections of the car at a time. You could finish the work on an area and spray some protective primer over it and then move onto the the next area.
Some brands of paint are allegedly better to work with according to those that do a lot of auto body work. SPI is one that gets a lot of recommendations but I think it costs a fair bit more. The Nason primer and paint I used is more of a lower end line of products but worked fine for me and others have found the same. Use a decent quality gun for the topcoat as they can make a big difference. A cheap gun for the primer is okay (like HF) and some guys just toss them with finished. Guns can be expensive! I suggest using a quality undercoat (if using any) and quality seam sealer. I had a big problem with the Proform undercoating and seam sealer I used. The undercoating sprayed over seam sealer really softened the sealer up even though made by the same company. Even the chemist at head office had no explanation. It took many months for the seam sealer to properly set up.
There are lots and lots of youtube vids out there but beware. Some are truly excellent but there's lots of bad info. and advice too and some are freakin' idiots. There are a few forums that are good like autobody101.com and hotrodders.com
Briefly:
If stripping to bare metal whether it's media blasting or using sanding/stripping discs, you've got to get primer on the bare metal pretty much immediately otherwise "flash" rusting occurs. You can't see it at first, but it's there and will ruin a paint job. Most people use epoxy primer on bare metal. It provides the best adherence and durability. Then you can use "high build" urethane primer over the epoxy. It sands easily and is excellent for smoothing out imperfections and high and low spots. The procedure is called "blocking" because you use sticky-back sandpaper on semi-hard rubber blocks (which come in various sizes and shapes).
Some folks put down the high-build primer first followed by epoxy, but I don't know why that would be better. Both are called "DTM" which stands for "down to metal". Epoxy primer is not easy to sand compared to the urethane primer. Once you have primer on, there is a window of only days to apply subsequent coats, whether it's more primer or the final topcoat. Reason is, the subsequent coats will chemically bond together otherwise you MUST sand down the primer to get a mechanical bond. Different brands of paints have different window periods and IIRC, SPI has the longest at 7 days. I used Nason primer which has a 2 day window so you have to work faster. If you're past the window, you need to scuff epoxy primer with sandpaper or scotchbrite pads. Hard to do in some places like underneath where there's lots of overlapping seams, nooks & crannies and hard to reach places.
Don't make the mistake of taking a body somewhere to get the entire thing media blasted and then think you can leave it bare and take months to work on repairs and mods and then spray primer on it. You can always remove primer from areas you want to work on. You can get a spot blaster or a pot blaster like the 40 lb one HF has. If wanting to media blast a body yourself, coal slag is a good media. Tractor Supply has some they call Black Diamond. Use the fine grit stuff. It's messy and it goes everywhere so you want to put up some temporary sheeting to contain it. You can scoop/sweep it up and screen it and put it back in the pot blaster. It's slow doing it yourself but works very well.
Primer can be applied over pre-existing paint in most cases if it's in good shape. Back in the 50s, Fiat used some kind of enamel over what I think was a red oxide primer (or similar). Technology has changed a lot but as long as the old paint and primer is in good shape, I think you should be okay to leave it on and just strip away what doesn't seem okay. The roof for example might be something that can be left on, but for the small area it is, you are probably better to strip it all off. Might even find bad spots under anyway. It might be a good idea to strip all paint and primer out of seams. Fiat used a lot of a type of putty on some seams and I would remove that if planning to paint over it.
Before spraying primer and subsequent coats of primer and paint, make sure to use wax and grease remover along with tack-free cloths.
Forget about using phosphoric acid metal prep products. Not needed and in some cases it's not compatible with primer and paint and can cause failures. Needs to be properly neutralized too. Best thing is strip to bare metal and get the primer on pdq.
One excellent filler is called All-metal. It can be applied over bare metal which really helps. The bare metal has to be super clean. The spray the primer over that. The All-metal doesn't have to be sanded out 100% perfect but need to sand down high spots. Once primer is on, then you use plastic filler (aka bondo) over any remaining imperfections. Seam sealer should be used over seams, joints and cracks.
There are various grits of sandpaper that should be used. More aggressive grits like 60 can be used on bare metal and first application of filler on bare metal. Then you work your way up to smaller grit paper to remove scratches. If using single stage urethane, you can stop at 320 grit. If using a base coat and clear coat, you'll need finer grit otherwise you'll see sanding scratches underneath.
If you are doing welding on any sheet metal, you'll want an angle die grinder and roloc discs. These are available in as small as 3/4" dia. up to 3" for larger areas.
If you're thinking of painting at home, single stage urethane works well. Doesn't need special equipment or paint booth. NOTE WELL that urethane primer and urethane topcoat paint is highly toxic because it contains isocyanate. You can't spray it indoors unless you have a supplied-air respirator setup (expensive). You can use it outdoors with a fullface respirator and the correct cartridges and are fully suited up because the isocyanate can be absorbed through skin. Urethane paint hardens quite fast and is even hard enough the following day to sand if needed.
If you have runs on the urethane paint or too much "orange peel" , it can be wet sanded with 600 grit paper ending up with 3,000 or finer. After that, 3M makes some excellent rubbing and polishing compounds.
The enamel that was used in the 50s wasn't high gloss and if you want your car to look more like it originally was, a base coat followed with a clear coat will look a LOT glossier and some may not be happy with it. There are flatteners that can be added to paint but they apparently are hard to get to work well.
If you are doing a restoration to bare metal over a long period of time, you kinda need to plan things out. You might for example, focus on the underside of the car first and get it primered and maybe rubberized undercoat over that is paintable (or leave it black). Then maybe do sections of the car at a time. You could finish the work on an area and spray some protective primer over it and then move onto the the next area.
Some brands of paint are allegedly better to work with according to those that do a lot of auto body work. SPI is one that gets a lot of recommendations but I think it costs a fair bit more. The Nason primer and paint I used is more of a lower end line of products but worked fine for me and others have found the same. Use a decent quality gun for the topcoat as they can make a big difference. A cheap gun for the primer is okay (like HF) and some guys just toss them with finished. Guns can be expensive! I suggest using a quality undercoat (if using any) and quality seam sealer. I had a big problem with the Proform undercoating and seam sealer I used. The undercoating sprayed over seam sealer really softened the sealer up even though made by the same company. Even the chemist at head office had no explanation. It took many months for the seam sealer to properly set up.
There are lots and lots of youtube vids out there but beware. Some are truly excellent but there's lots of bad info. and advice too and some are freakin' idiots. There are a few forums that are good like autobody101.com and hotrodders.com
Last edited:
flaviaman
True Classic
Hi Gill:
Thanks so much for taking the time to compose this, I am looking to paint a few items and have been wading through so much info, your explanation is concise which I appreciate.
I do not believe we have ever met, unless you are a long time member of VRCofBC, you were however kind enough to sell me a set of CD-3’s a few months ago, thank you again.
boxy02
True Classic
Great write up, Gil!
I have had very good luck with TCP Global (San Diego, CA). I did a partial bare metal job on my BMW 2002 using Kustom House DTM (direct to metal) now called DTS (direct to substrate) epoxy primer on the bare metal. It can also be used as a sealer immediately prior to top coating. I used Evercoat Featherfill G2 polyester primer surfaces to fill body filler and kitty hair filler and then block with 80 grit to get it flat. A spritz of black spray paint from a distance of 1.5-2 feet from the panel can be used as a guide coat to weed out the high and low spots which will need more attention and more primer before blocking more. Then block-sanding with finer sandpaper (80, 150, 220, 320, 400,...) until you're ready for top coating. That's when you can shoot the DTS as a sealer and in the time it takes to clean your gun, you're ready to shoot single stage top coat (I used Restoration Shop line acrylic enamel from TCP Global). Many factory color codes can be found at TCP website and they'll mix it up and ship it to you. Reasonable prices as well. Good luck and take your time! I'd steer clear of PCL products, they react with many other products and fail. One more thing, providing both mechanical (sandpaper or scotchbrite red or grey-not green, that's for dishes) and chemical adhesion before applying any primer or paint is much better than only having one or the other.
I have had very good luck with TCP Global (San Diego, CA). I did a partial bare metal job on my BMW 2002 using Kustom House DTM (direct to metal) now called DTS (direct to substrate) epoxy primer on the bare metal. It can also be used as a sealer immediately prior to top coating. I used Evercoat Featherfill G2 polyester primer surfaces to fill body filler and kitty hair filler and then block with 80 grit to get it flat. A spritz of black spray paint from a distance of 1.5-2 feet from the panel can be used as a guide coat to weed out the high and low spots which will need more attention and more primer before blocking more. Then block-sanding with finer sandpaper (80, 150, 220, 320, 400,...) until you're ready for top coating. That's when you can shoot the DTS as a sealer and in the time it takes to clean your gun, you're ready to shoot single stage top coat (I used Restoration Shop line acrylic enamel from TCP Global). Many factory color codes can be found at TCP website and they'll mix it up and ship it to you. Reasonable prices as well. Good luck and take your time! I'd steer clear of PCL products, they react with many other products and fail. One more thing, providing both mechanical (sandpaper or scotchbrite red or grey-not green, that's for dishes) and chemical adhesion before applying any primer or paint is much better than only having one or the other.
myredracer
True Classic
TCP is a great for buying automotive tools and paint supplies. I've bought a few things from them. I don't like Eastwood. They're like a bunch of amateurs and I refuse to buy from them. Their videos aren't worth watching either.
I don't know about around the US, but here, one major body shop supply chain stopped selling to the public about a decade ago. But there's another independent shop that does. You can talk to them and get advice on what products to use. Another nice thing about a local supplier is that when you run out of something or need something else, you can get it quickly. I get a small discount too which helps. I bought some "gun wash" (for cleaning out guns) yesterday. Had to pay over the phone and the guy left it outside for me so now you kinda need to know what you want and can't go inside to look at anything or take anything in for them to look at like say, matching a paint sample you have.
myredracer
True Classic
If anything I said actually helps anyone, great!
Way back in the 70s, I got my novice road race licence at Westwood in Port Coquitlam (near Vancouver BC) before vintage racing even existed. That track was legendary in the road race world and was kinda like the Laguna Seca of the PNW. Shortly afterwards, we moved to Vancouver Island (where I was for 20 years) and that was the end of my racing endeavors. I think it was in the 80s that they bulldozed the track and turned it into a subdivision. The new race track in now way out in the Fraser Valley and is flat and nowhere as much fun (IMHO). I've never been a member of VRCBC but have thought about in recent years.
You need to get those CD3s painted!
myredracer
True Classic
One important I'd like to add that I should have included is on compressors. I can't emphasize enough how important it is to have a good setup if painting or running air tools or media blast cabinet. Water & oil in paint & primer will ruin a paint job, water in tools will shorten their life and you don't want moisture in a blast cabinet or pot blaster.
You need plenty of continuous CFM available at 90 psi for tools and blast cabinet or pot blaster. For HVLP guns, you'll need 30 +/- psi at the gun. This typically means having a 5 HP 60 gallon upright compressor. I found a used, almost new one on CL at a good price. And you need the air to be clean and dry. Compressing air causes the air to contain a lot of moisture as well as oil droplets. The air needs to be cooled before it gets to the point of use and drained. It's amazing how much water comes out the bottom of my compressor. I have a HF auto-drain on mine and a hose to a bucket. I installed about 40' of 3/4" copper tubing on the wall. Some use a radiator setup. After the tubing, I have a dessicant dryer and filter for dry clean air and regulator, then I have another regulator that doesn't run through the dryer & filter.
Couple more things:
You can mix a small amount of epoxy primer & activator and apply it with a brush over clean bare metal. Works well for small parts, suspension pieces or the backside of metal patches or panels you're going to weld in place that you can't get to afterwards. You can use a quality rattle can spray over it within the recoat window. I really like the Professional series Rustoleum rattle can paint. 2K epoxy primer in a rattle can is available but is expensive and once activated is only good for max. 48 hours.
On media blasting a body, another approach is to media the whole thing, or maybe all of it except underside. Then do all of your rust repair and mods and filler + blocking knowing that it will flash rust anyway. Then when finished, do a thorough final media blasting before spraying the epoxy primer over everything. The first go at removing original paint + primer and maybe bondo takes a lot of time compared to removing flash rust. I've got my 850 coupe shell on my rotisserie and have done all the repair work by just using a strip disc on areas I need to get to bare metal. Then this summer I'll get the shell outside and blast the entire thing.
On the exterior of a body, which typically has open and easy to access surfaces, there are various strip discs types & sizes that can be used to get down to bare metal and can be used on pneumatic or electric tools. These work great if you have say isolated areas of repair you want to work on before stripping the entire thing prior to primer & paint. Strips discs are very dusty though. I've done it inside while holding the nozzle of a shop vac hose next to it, but is still messy. I was at a Habitat for Humanity store that sells donated tools and building supplies last year and they had a couple of boxes of 3" strip discs for a buck apiece so I bought them all. Strip discs tend to be expensive and don't last that long though.
You need plenty of continuous CFM available at 90 psi for tools and blast cabinet or pot blaster. For HVLP guns, you'll need 30 +/- psi at the gun. This typically means having a 5 HP 60 gallon upright compressor. I found a used, almost new one on CL at a good price. And you need the air to be clean and dry. Compressing air causes the air to contain a lot of moisture as well as oil droplets. The air needs to be cooled before it gets to the point of use and drained. It's amazing how much water comes out the bottom of my compressor. I have a HF auto-drain on mine and a hose to a bucket. I installed about 40' of 3/4" copper tubing on the wall. Some use a radiator setup. After the tubing, I have a dessicant dryer and filter for dry clean air and regulator, then I have another regulator that doesn't run through the dryer & filter.
Couple more things:
You can mix a small amount of epoxy primer & activator and apply it with a brush over clean bare metal. Works well for small parts, suspension pieces or the backside of metal patches or panels you're going to weld in place that you can't get to afterwards. You can use a quality rattle can spray over it within the recoat window. I really like the Professional series Rustoleum rattle can paint. 2K epoxy primer in a rattle can is available but is expensive and once activated is only good for max. 48 hours.
On media blasting a body, another approach is to media the whole thing, or maybe all of it except underside. Then do all of your rust repair and mods and filler + blocking knowing that it will flash rust anyway. Then when finished, do a thorough final media blasting before spraying the epoxy primer over everything. The first go at removing original paint + primer and maybe bondo takes a lot of time compared to removing flash rust. I've got my 850 coupe shell on my rotisserie and have done all the repair work by just using a strip disc on areas I need to get to bare metal. Then this summer I'll get the shell outside and blast the entire thing.
On the exterior of a body, which typically has open and easy to access surfaces, there are various strip discs types & sizes that can be used to get down to bare metal and can be used on pneumatic or electric tools. These work great if you have say isolated areas of repair you want to work on before stripping the entire thing prior to primer & paint. Strips discs are very dusty though. I've done it inside while holding the nozzle of a shop vac hose next to it, but is still messy. I was at a Habitat for Humanity store that sells donated tools and building supplies last year and they had a couple of boxes of 3" strip discs for a buck apiece so I bought them all. Strip discs tend to be expensive and don't last that long though.
Oriebi
Daily Driver
beautiful post!
@redracer: you are very smart, you have done a great job with your 600 and you demonstrate it by giving excellent advice with a wealth of fundamental details for the restoration of a historic car.
This is my work, and I couldn't have said better.
@ 59 600: One thing, when you weld the sheet metal, the internal part which is not reachable in the future, treat it with a simple galvanizing spray, it does not interfere with the welding and will protect it against any rusty inflorescences. At the end of the work, with a gun and cannula, a waxy protection (type 3M) is sprayed inside the most difficult to reach boxes, so the work done is safe.
Have a good job and don't rush!
@redracer: you are very smart, you have done a great job with your 600 and you demonstrate it by giving excellent advice with a wealth of fundamental details for the restoration of a historic car.
This is my work, and I couldn't have said better.
@ 59 600: One thing, when you weld the sheet metal, the internal part which is not reachable in the future, treat it with a simple galvanizing spray, it does not interfere with the welding and will protect it against any rusty inflorescences. At the end of the work, with a gun and cannula, a waxy protection (type 3M) is sprayed inside the most difficult to reach boxes, so the work done is safe.
Have a good job and don't rush!