What is the difference between primer and sealer in the automotive paint industry? This is a great question and could lead into a forever explanation. However, I will make it as short as I can. Primer is basically a material to make something ready for the next stage. Sealer is pretty much self-explanatory. An automotive paint sealer, is a barrier that seals in everything under it and all above it.
What Is Primer?
Most primers today are urethane (2K Primers). They are great for filling and building layers you can block sand down. You can build far better with urethane than with the old lacquer primers. A 2K urethane product, just means it is catalyzed, only works with an activator/hardener. This type of primer can serve as a sealer. However, primer is mostly used to spray over damaged and repaired areas to create a level and protected surface. Nason makes a really great Urethane Primer, easy to mix, spray and sand.
In order to create a waveless surface, you have to build up your layers of primer. Spray three or four coats, then block sand level and smooth. In 
many cases, you are going to cut through the primer on the high areas. This may require applying more primer and block sanding to create a waveless surface.
After your last block sanding, and you are happy with the surface, apply at least one more coat of primer. Do a medium wet sanding with 400 grit. Once dried, cleaned and wiped down, you are ready for a 2K sealer. The sealer is designed to bond with a topcoat, so no sanding it. The sealer is used to protect the topcoat from any areas where you have sanded through the primer. Also, the sealer is to promote adhesion for the topcoat. Most sealers are color shaded for maximum topcoat coverage.
Why Color Your Sealer
When you buy an automotive paint, the paint store should tell you what color sealer to use. This is called “shade factoring“, it allows your topcoat to cover with less coats. Imagine trying to spray white over a red surface, it is going to take much more paint to cover and to look uniformed. This is a basic example, but you would spray a silver color over a grey sealer. You would spray a black 
over a black sealer. White sealer would go under a white paint.
At one time, you could buy sealers in colors, or tints to shade them. Now they have figured that shades like white, grey, black and dark grey will enhance coverage just the same. I have been using Cromax 2K sealer brands for years. I have always got great results with their three different shades. Sadly today’s paints have less pigment in them. This makes them more see through, so you need a shade that compliments the topcoat being applied.
To give you an idea of what spraying your base color over top a non-uniformed colored surface would be like. When sanding a surface, you are going to cut through high places. This doesn’t matter if the surface is paint or primer. The surface will become multi-colors of dark and light patches.
Unless you apply many coats, you will possibly see those dark and light patches in your paint job. Same theory applies if painting for example a red, over a black primer. Unless you apply enough coats, the red will tend to be a shade darker, especially if it calls for a white or gray sealer. However, a uniform even color underneath the topcoat, will cause a nice uniformed look.
Why Not Use Primer For A Sealer?
Primers are porous and are not really designed to be a sealer per-say. They are 
designed to be used to fill mild waves and scratches. It also adds a protected layer between bare metal and your topcoats.
Paint can be applied over primer. However, if you would like to increase the life of your paint job and prevent having any surprises show up later. You will want to use a good 2K sealer for the best job.
If you are just wanting to get by and keep the cost down, you don’t have to use sealer. However, this is based on that you are using a 2K urethane primer. As mentioned, primers are limited in colors, so be prepared to use more paint to provide an even uniformed surface. The primer has to be sanded, to promote adhesion for the top coat. If you have sanded through the primer in any areas creating color patches, this could create issues with top-coating.
When using the primer as a sealer, the primered surface has to be all even with no sand through spots. It cannot have color patches as this will make covering it with a color difficult. Also, sealer helps solvent lifting. Urethane primer will offer a barrier to keep the topcoat solvents from penetrating old paint. However, if you sand through to the old paint, you are running a risk.
The Benefits Of Sealer
Sealers are not porous, it will resist absorbing water or moisture. Primer can absorb moisture and it can become trapped. A 2K sealer creates a water tight sealed barrier between the prepared surface and the topcoat. You are also reducing the chance of solvent lifting or reactions when using a sealer. Topcoats are mixed with solvents to reduce and activate them. These solvents can penetrate through a primer and react with the old paint. The reaction usually looks like acid eating the paint, it is called paint lifting. Using a 2K sealer eliminates this from happening.
Sealers are also adhesion promoters. It will adhere to the prepared surface like a glue, but also does the same thing for the topcoat being applied. The most common sealers are the non-sanding types. This is the best method, as you get a uniformed color with no chance of sanding debris. You spray it on, and it is ready to be painted.
Sealers also reduce the chances of getting fisheyes in your topcoat. If you topcoat over sanded primer, there is always a chance of sanding debris. As mentioned, primer can also retain moisture, these two combined can create fisheyes.
A sealer gives your topcoat an even uniform shade to increase topcoat coverage. The sealer acts as an adhesion promoter that bonds the topcoat to the vehicle’s surface. You get a protection against solvent reactions. This inhibits the topcoat eating into the old paint, or the old paint reacting with the new. By using a sealer, you increase the life of your paint job and reduce the chance of a paint failure.
Use A Non-Sandable Sealer
There are sealers that require scuffing or sanding, I do not recommend these types. I have quite a few reasons for not liking these. Wet sanding or scuffing causes debris build ups in cracks and corners. This debris will cause fisheyes and the paint will not stick. Do a good detergent wash after your final wet sand before painting. A detergent wash ensures that all the nooks and crannies are cleaned out. Sadly, there are 
always some debris left here and there. Sealers and primers tend to melt in these places and create a bond-able area.
If you use a sealer that has to be sanded before painting, then that debris will cause paint failures. Like I said, primers and sealers tend to merge and melt into these debris areas. Paint isn’t that forgiving and will more than likely fisheye. This can be avoided by using a “Non-sandable” sealer. Some people are old school and feel the topcoat will not stick to the surface. Rest assure, these sealers are designed to bond with the topcoat. Better than sticking to a sanded surface.
So a non-sandable sealer will create that layer for bonding. If you so get dirt in your sealer, you can always nib out the dirt with a small piece of sandpaper or scuffy pad. Then carefully wipe the nibbed area with a tack-cloth, no solvents of any kind can be used.
Can You Spray Primer Straight Over Metal And Fillers?
Technical manuals and auto body teachers say you can apply a urethane primer straight over metal and body filler. I don’t fully agree with this, yes it can be done, no I don’t think it is the best method. I recommend spraying an etching primer first. Not a thick heavy coat but a light to medium wet coat. Scuffy it after it dries, and then apply your coats of urethane primer.
The reason I do not fully agree with applying a urethane primer over body filler and metal areas. Obviously metal and body filler are two different materials. Basically body filler is plastic, and plastic and metal have different compositions. So with temperatures, solvents and other natural elements they get exposed to, it can force a paint blemish. If you can imagine an area in the middle of your quarter panel that has been filled with filler. The panel was sanded back to the metal, filler was applied and sprayed with urethane primer. After it is painted, and it has been exposed to the elements for a month. Get down and look at it at an angle, you possibly can catch where it was filled.
Surface Material Differences
This isn’t because you did bad body work, it is the differences in materials underneath the paint. Cars up to the early 40’s used steel that wasn’t high in carbon. The carbon tensile strength was lower that cars produced latter on. This made the metal seem softer when it was hot. I tried filling two holes in a trunk lid on a 1932 Oldsmobile. I welded 14 gauge steel in the holes, and then skimmed it with body filler. The trunk was black, so when in the sun, it got extremely hot. Once it got hot, you could see the areas I welded up. Not in color but it looked like dents. Then it came to me, two different kinds of metals expanding and reacting to heat differently. I ended up leading the holes and problem solved.
This will apply with primer over fillers and metals, especially if in the same area. An etching primer will eat into the filler and into the metal. This gives your urethane primer a uniformed area to be applied to. Since the etching primer will bond with the filler and metal, the urethane primer will bond into the etching primer. This gives you better adhesion, and reduce body work failures later on.
My Recommendation
I recommend using sealer because you will use less paint and get a longer lasting job. You don’t have to sand it, and a good sealer is designed to promote adhesion between the car surface and the paint. Using primer only can result in fisheyes and possibly a higher consumption of paint. As I mentioned, the difference between primers and sealers, primers have limited colors and shading is offered in sealers. So that is pretty much the difference between primer and sealer on a vehicle.
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How long is the sealer good for after spraying it before you put your basecoat on ?
You do not want to wait more than an hour on most sealers. I think many say up to 2 hours. If you wait too long, you will have to use a scuffy pad to rub the surface before applying the paint. If you spray your basecoat within an hour, you should be OK. It is important that you ask your paint supplier or read the specs on your sealer as many are different but a rule of thumb that I use is between 30 minutes and an hour. Let me know if that helped. The sealers I use are 2K and I usually try to get the basecoat on between 30 and 45 minutes.
Thanks for this article, helps a lot. Been struggling to wrap my head around this. So in the cases where you use primer, you recommend following with sealer after leveling the primer?
When can you get away with just using base coat? In instances when you don’t sand through the original base?
Thanks!
These are great questions, I will try my best to explain. For the best long lasting job you can get, you will always want to use sealer and here is why. Paints, regardless if it is a base coat clear coat job or a single stage, they have solvents in them, partly to thin it and part what they are made of. These solvents will basically soak into the old paint or primers, depending on what surface you are spraying over. Once the solvents start soaking in, they will lift the old paint or primer almost like paint remover. Sometimes this process can happen instantly or take up to a few months. But you will see it and this can start peeling and flaking.
Primering is mainly used for leveling a surface and fixing blemishes but it too can help seal the surface underneath. In the old days, primers were mostly lacquer, which enamel paints laid on top really well as enamel solvents cant cut lacquer. Although you will find all sorts of information saying I am wrong but to me, the proof is in the pudding. You can reduce enamel with lacquer thinners but you can’t reduce lacquer paints with enamel reducer. You can rub a rag soaked with enamel reducer all day over top a lacquer finish and it won’t hurt it but take a rag full of lacquer thinner over an enamel painted surface and see what happens.
Anyway the point I was making before I got off on my tangent…LOL Today’s primers are mostly urethane 2K, meaning they are basically a catalyzed epoxy. So a urethane primer can act as a sealer and if all you are going to do is lightly sand it or just scuffy the surface and not cut through the surface of the primer back down to the original surface, you could paint over this without using a sealer. The main reason for using a sealer over top a primer is, usually based on the idea that you are going to sand the crap out of the primer to get a level and slick surface. And in that process you are going to cut through to the original surface in many areas. So you spray a catalyzed sealer over all the work you did and you will get a long lasting and uniformed job.
The one issue you will have with using primers as a sealer is that they do not come in shades. It has become ridiculous these days, but we pay almost 400% more for automotive paints now and sadly they have become thinner and don’t cover worth a crap. So to solve this issue, they make sealers in shade factors so that your base coat covers better. Usually the shades run as follows and this is the basics: White, Light Grey, Dark Grey and Black. Depending on who the paint manufacturer is, there may be more shades than this or less.
I hope that helps clear up some of the confusion, if not contact me through the contact page here on my site.
It does, thanks for the detailed reply! Much appreciated!
More than happy to help, sorry my explanation was so lengthy but I wanted to write something others can read as well and for it to help them.
Rodney, thank you for that forum, I have been painting for forty some years and knew about what you are talking about, and in all that time I can’t remember that I have had a problem like i am having now. I am doing a vw bus (70) complete, and somebody had put i don’t know what ,of bondo concre3te as filler on it. I should have (hind sight) taken ALL of it off but went through a pack of 36 grit grinding disc and it still wasn’t coming all the way off, so I went and mixed bondo and thin coat over it did my thing and got down to sanding and finish prime glazed ,everything put super light coat of paint color and HERE THEY COME, pinholes in different areas,NEVER HAD I HAD THIs PROBLEM, I failed to tell you the new owner of the bus had put epoxy primer over all thie Before I did any work on it,so after reading your blog I do believe in sealing this bus . also, some of the primers you use to be able to reduce it down a little more and it becomes their sealer, remember that ? I also agree with you on the amount of pigment you get in paints today compare to some years ago, a 4.6voc with good pigment in it was less toxic to the enviroment than todays 2.6-3.1 voc because you have to spay most cars twice compared to once before ??? to get the same amount of paint on the car that is going to last. anyway thank you for your input it helped ,Donnie
I have ran into the same issues in the past. Actually my 71 GTO has a big wing looking spoiler on the back and someone tried fixing it with a marine glass I think. I had to take my 9 inch grinder with a stone to cut the highs down. Then when I would try spreading a quality body filler over it, it kept making little pinholes in the filler. My guess is, even though it seems aged, hardened and cured, once you cut into it, it releases a reaction that is still going on with it. It may be possible they didn’t mix in enough hardener or too much and that causes gasses to expel.
I mean what to you do though? Especially if you run across an entire panel that is just coated in someone else’s bad mix. I guess a complete grind out is all you can do but man that sucks, so much time and mess, not to mention the risk of damage to what lies underneath it. I couldn’t grind to much on my spoiler as I was afraid of tearing it up. I eventually sealed it with an epoxy primer that I thinned down so it would work its way into the pinholes. I have since then bought a new spoiler as it was cracking apart in other places later on. But what a headache.
I am appalled at how much they charge for thinned down paint now. I was told paints went up back around 911 when gas prices sored to like $6 a gallon. Oil was high per barrel, and since paints are made from oils, it made sense that they would go up a little. But they shot up over 400%, they thinned out the pigments and frankly, overall, it just doesn’t perform the way it used to. And of course, the cost never came back down when oil prices dropped. In fact, the prices just keep going up, talk about price gauging. I had always been a DuPont man, loved shooting their paints and loved their whole systems they had. But since then, DuPont dropped the automotive paint line, Axalta bought their paints and now it isn’t that great. The only thing they have over everyone else is their color matching. Chromabase is still one of the best when it comes to matching. You can’t buy Uro-Prime in the basic automotive paints anymore, it is now considered commercial and industrial. You can buy it but it is priced too high and has to be special ordered. The Nason’s urethane primers are really good, but I really liked that Uro-Prime 1140S.
I am glad my post helped, if you ever have anything you want to bounce off me, just give me a yell.
I have a VW beetle 1972, think it has two coats of primer then it was sprayed with car wrap, that’s is like a rubberised paint. I have managed to remove this and suspect the two coats of paint remaining are cellulose. What should I use to seal the surface before I use a cellulose base colour?
I am not real familiar with cellulose but from what I remember isn’t is lacquer based? I hate that plasti-dip rubberized coatings, guess it would be OK if you are planning a bank robbery and wanted to change the color of your car real quick, otherwise that stuff is expensive and really a waste of time. If you are going to hassle with spraying it, just paint it for real.
Anyway, I would sand the two coats of primer down, meaning block sand it really good so you get the surface level and slick. Plus this will give you an opportunity to ensure there is nothing wrong beneath the outer surface of the primer. If all looks well and you see no signs of primer bubbling or possible reactions where the primer went over the original surface, I would get a 2K sealer and apply one good medium wet coat. Then spray it with your cellulose.
I apologize to bring this back from the dead, but the OP similarly reflects my current concern with my project. I recently picked up an E30 BWM 325i that was plastidipped, and I am planning on repainting it soon with a single-stage paint. According to the previous owner, the car was fully prepped for paint (i.e. sanded, primed, then sealed with urethane paint), but ended up plastidipping since the topcoat color was eventually undecided. Right now, the body panels are all in very good shape with no visible dents or unleveled surfaces, so I believe bodywork was indeed performed prior to the plastidip. Old pictures of the paint-booth-ready car further supported the condition of the body. Now, I’m planning on tackling the paint job myself as my very first automotive paint project, after having my other car recently repainted with single stage by a pro who graciously gave me many pointers on starting my own DIY project.
I have not removed any of the plastidip yet, but there are spots where peeling or bubbling is starting. So, the research and prepping are now in full swing.
With ALL that said, given there’s no apparent defect seen after removing the plastidip, is there a way for me to gauge the condition of the sealer before spraying the first layer of single-stage paint? I would prefer to reuse the sealer if that’s possible, instead of sanding everything down and respraying from bare metal.
Any tips or feedbacks is appreciated!
You do not want to use the sealer that is under that Plastidip the way it is. You will want to sand it but there is no need in sanding it all back down to metal. Just evenly wet sand it with 400 grit paper. Once sanded, wipe it down with a detergent wash and then a prep-solvent. Mask it off, apply one coat of a fresh sealer on it, give it no more than a 30 minute flash and paint it. That should be all you need to do unless there is damage or you might find bubbling or reactions from previous body work. If it all looks good, sand it, seal it and paint it.
Great help! Quick scenario and question…I had some imperfections and low spots when I applied my sealer. This meant I HAD to sand my “non-sanding” sealer. After sanding, I still have very small low spots in the sealer. Tech sheet said I must scuff the sealer after eight hours to promote adhesion. Does this mean my pant will not stick in those very small low spots. As I am unable to scuff them? I’m not worried so much about a perfect look when I’m done, it’s more of a “just gotta get the car going again” situation at this point!
Any help is GREATLY appreciated!
If you sanded the non-sanding sealer, you can certainly scuff it. I would scuff the low spots to help promote adhesion. However, you will not be able to wipe the sealer surface with any solvents. Any attempt, you will find your rag melting into the surface. Wipe it down with a clean diluted liquid detergent water, you could mix in a small splash of isopropyl alcohol into the water. But definitely scuff the surface, that will make it adhere and it should last.
Great information. Thanks
I want to re spray my VW bus in 2k but the current paint job is lacquer, if I apply a 2k sealer will it react with the lacquer
Some of your paint store people will tell you that you can spray lacquer over enamel and that enamel can’t be sprayed over lacquer. These people are STUPID, I have painted for over 40 years and here is the reality. You can spray enamel and urethane all day long over lacquer, will not react or hurt anything. However, you cannot spray lacquer over the others. Here is why and it is so common sense. What do you use to clean your spray gun up with? Lacquer thinner.. You can try using enamel reducer but you will find out really quick that it just won’t cut the paint residual out of the gun. But to help you, I have painted many lacquer surfaces with 2K products. Just sand it and apply 2 coats of a 2K urethane primer and sand, prepare, seal and paint. You will be fine. But if you are still concerned, you can always test a small area with 2K primer and make sure there is no reaction, there won’t be but for your own peace of mind.
OK thanks, do I need a full face air fed respirator for the 2k products or will my 3M half mask with correct cartridges be ok
As long as you are not trapped in an area where there is no air flow, you should be fine with a half face. If you are going to be painting a lot, then I would get a full face and a fresh air system. But for one car it isn’t necessary. Just make sure you have air flow or do it outside and you should be OK.
Rodney, I do agree with what you are saying about the enamel over lacquer paints and not vise versa, however what I firmly believe is that you can spray enamel over lacquer BUT after lacquer is sprayed it MUST dry and cure completely, which in my experience takes up to 3 months ,otherwise there is a high chance that you can get cracking or what road maps under the enamel the solvent in the lacquer takes time for it to escape so you don’t want to “trap” those under you enamel. it dries fast but just on the surface not deep under, just give it some time before applying the enamel
Yes I agree 100%, the lacquer has to be aged some before shooting anything over it really. But the paint stores are now telling me that you can’t spray enamels or urethane over a lacquer job period. Makes me wonder what drugs they take. They are trying to tell me that the solvents from enamels and urethanes are eating down into the lacquer and causing it to lift. That is insane, enamel will never penetrate lacquer, especially if that lacquer job is into being years old. If gasoline and oil can’t lift or eat lacquer, enamels and urethan reducers sure won’t. I also have the paint stores now telling me that they will no longer carry mid-coat adhesion promoters because that too is causing the top-coats to lift. I have been using mid-coat adhesions for as long as they have been making them. I have never had an issue. Makes me wonder where they are getting this false info from.
I used an epoxy primer that was like a sealer on a bumper that used an epoxy activator. I then let it dry and lightly scuffed it, used a lacquer based primer and it was melting the sealer away. What is my problem?
I am not sure because anything epoxy, once cured resist lacquer and enamel solvents. I have been using 2K Urethane primer for years, that is an activated primer, and I have put lacquer paints over top of them and never had an issue. Please tell me what brands you used and how you mixed them. Both in your epoxy materials and your lacquer primers and I will look into this for you.
I am unclear why you put down a sealer, then the primer over that. I would have done all my body work with fillers and primers first, then used the sealer before top-coating. Reply back or contact me through my contact form and you can tell me more of what is going on. I do know that automotive paint manufacturers are making it harder and harder for those who like to use lacquer products. The materials are getting harder to find, so many are using the 2K primers, I am one of them but never had a reaction. It could be the brand you bought or did not actually activate it.
every place i’ve been to does not have paint sealer and does not sell it, and instead try to sell epoxy primer in its place. ??
I can certainly understand the aggravation, I swear knowledgeable parts and paint people are becoming scarce. No worries, here is what I use and you can get it at any O’Reilly Auto Parts store. O’Reilly is a seller of Nason products, so even if they do not have it in the store, they can order it. If you have no one in your area that can sell you these products, let me know and I can send you links to comparable products that you can order online.
First you want to prime the areas or the whole panels you have done work on. Sand that level and slick, no finer paper than 400 grit. You may not need to prime any damaged areas, in that case, you just need sealer. No matter either scenario, once the surface is sanded, clean and grease free, you will want to seal it. These days, sealers are sold in what is known as shading factors. Meaning White, Gray and Black. The reason for this is so that you color you will be covering the sealer with will cover quicker and more evenly, causing you to use less paint on your first applied coat.
Here are the numbers and what you need to know on the primers, sealers and activators.
Use Activator 483-87 or 483-88 for all these listed below. 483-87 is for mid temperatures and 483-88 is for high temperatures
Nason 421-19 Gray Urethane Primer
Nason Select Seal 2K Sealers (Gray) 422-50 – (White) 422-51 – (Black) 422-52
You can seal your surface with a no urethane sealer. The 1K sealer doesn’t require an activator and works just fine on most surfaces you haven’t cut through the original paint when sanding. If you have done a lot of body work of cut heavily through the orginal surface, I recommend the urethane sealers.
Nason Select 1K Sealer (Gray) 422-23
You can reduce your urethane primer a little, no very much, no more than 5 to 10% to get it to flow a little smoother if you are in a hot dry area. Usually you don’t have to reduce it. But if you do, then use Nason 441-21 or any brand of Urethane reducer.
Let me know if you need an alternative if you can’t find an O’Reilly or an automotive paint store that sells Nason or can’t convert these numbers to their brands. But follow my above procedure, this is how it is done.
One question that I can’t seem to find an answer to (which may mean it’s obvious and I’m slow 🙂 is can you spot seal a panel instead of painting the whole panel?
I have have a vehicle that took guardrail (small) damage all the way down one side. Since the repair areas are limited to the about six inches vertically I’m wondering if it’s possible to just seal those areas without applying it to the whole panel? Basically, 80% of the area of the vehicle I’m re-painting already has a good base coat. I just don’t want to waste time and material if it’s not necessary to seal the entire right side of the car.
Hey Alan, the answer is yes, actually this gives me a good topic for a new post to write soon. I understand what you are wanting to do and I have done that. The method would be to make your dent repair, fill if you have too. Shape and smooth it. Prime it but keep your primer just to the area you are working. Wet sand it, if you are happy with the repair. Then spray sealer onto the repair area and then fan it out just a little beyond. Tip, get your sealer in the correct value shade. If you are not sure what that is, you want a sealer shade that compliments the color you are spraying so that you do not have to put 4 to 5 coats to cover it. Sealers come in dark gray, light gray, black and white. Now if the color of your vehicle is close to a light gray shading, you can just use your urethane primer as a sealer. If you watch this video where I repaired a rear bumper on a Toyota Highlander, you can see how I just used the primer as sealer but I did so because the color in one coat covered. Of course I used 3 medium coats and fanned the color out in a larger area each coat. That is called blending. https://www.youtube.com/watch?v=NNpp6ITqCdE
I hope that made sense, if not, contact me through my contact page on this site and I will try to do my best to help you
I’m planning to repaint a 84 RX7. It was brown from factory, has been painted a candy apple red, the door panals came out darker than the rest of the car. Then it was painted black which cracked. This was all done before I got the car. I have been sanding the car with 150, then 220, and 400 grit wet/dry paper. Question I have is can I just use a sealer over the old paint some red is showing through or do I have to prime first? I’m painting the car the original brown it was so it matches vin.
Glad you wrote in, but I am worried about the black paint that was cracking. All of that black paint needs to be sanded off, it will come back to haunt you. First off, how are you sanding your car? Are you doing it all by wet sanding? In all honesty, I think I would have used a paint stripper and pulled off the black paint. If it is cracking, this means several things. It was mixed wrong when they sprayed it, or they didn’t prepare the car properly and the paint isn’t really adhered to the red paint. Or the red paint is breaking down due to a reaction with the black paint. I know this sounds like more work than you would want to put in but sealers and primers will not help or stop the failing or breakdown going on underneath. I would get some CitriStrip paint remover. I like it because it isn’t so strong it strips the paint all the way down to the metal, you can take layers off at a time. I would at least get the car back down to the red coat and look for cracks. If there are none, you can sand that layer. I would use a DA Sander, wet sanding is for blocking and finishing, not the initial rough down. Strip one panel down to the red, pick a panel that is cracked the most. Once you have it down to the red, inspect it. If it is good, DA sand it with 120, 180 and or 220, this depends on how much black paint is left and how hard it is to sand off. Get a good sanding on the red layer, then prime it with about 3 coat of a urethane primer. Do this for the whole car. Once you have the entire car in primer, wet sand (Block Sand) it first with 320 grit to level the surface out of any waves. Then go back over with 400 grit wet sanding. It is OK if you sand through some spots, that is what the sealer is for. Since this car’s undercoats are questionable, I would use a 2K sealer. Then immediately apply you brown paint. I know that isn’t what you wanted to hear, but if you want the paint job to last, get rid of whatever is cracking, just sanding the cracks out isn’t full proof, you need to know how deep they are and what caused them. Send me pics and if you need further help, contact me through the contact page on this site.
Here are some materials I would suggest for stripping and sanding
CitriStrip: https://amzn.to/3k0E3jx
Plastic Razor Scraper: https://amzn.to/3iT8eK5
Electric DA Sander: https://amzn.to/2XzhDOJ
120 Grit 6in DA Paper: https://amzn.to/3iTcrgL
180 Grit 6in DA Paper: https://amzn.to/3iQaIsG
220 Grit 6in DA Paper: https://amzn.to/3g9caVo
Of course it may be easier to get all this from your local automotive paint store. But this should give you an idea.
Let me know how this job turns out, and send me pictures. Not sure if you saw this video, but I did a black Miata that had got one of those $99 paint jobs. I had to sand it back down to the original black paint. I primed it and sealed it. You can see the results of a little hard work: https://youtu.be/efL6E9koDjA
Thanks
Thanks for the oppurtunity
What are you thoughts on properly painting bare aluminum panels? I have a set of custom fabricated aluminum doors for my Jeep and most places didn’t have a clue about painting aluminum.
One shop stated that they would do it and use a sealer and then paint on top. He stated they did bare aluminum ambulances before. Does this sound correct?
I have painted aluminum forever, since I started painting really. I always use Variprime, it is a self-etching primer. Many companies make a self-etching primer but they are not as good as Variprime. Most are a one step ready to spray product. Axalta’s Variprime uses a converter, you have to wear a mask to spray it. You can look at the specs here: http://products.axaltacs.com/dcat/us/en/dr/product/615S.html
It is expensive now, but luckily Nason has a similar product for less bucks. You would need Nason 491-17 and the activator 441-43. These can be bought at O’Reilly Auto Parts. I prefer the Variprime but like I said it isn’t cheap. You do not need to put on a heavy coat of either one. I usually spray a coat on and then let it dry for a day. I go back using a scuffy pad, I do not sand it. I wipe it down and then spray my regular urethane primer over it so that I can block sand it to perfection. Then I seal and paint.
I plan to start a car body repair because I believed my ample skill in smaw and tig weld plus my would be knowledge I would get from you in paint, I would be ready to start it soon. Thanks!
It is very helpful.