Paint adhesion .

[Fordestes]

What is the best surface prep and primer paint for my 30 coupe ? I am planning to do the body and paint , the way it is now the paint is curling up and flaking off, I agree this will happen due to no primer been used , about every model A I have seen the paint flakes off after a few years , what primer and finish coat will stay on beside Imron ? I thing the key is good surface prep, what do I need to sand off old paint , clean the metal and prime for longevity ? Thanks, D. Estes

[J Franklin]

You need to sand after a thorough cleaning to get all oils and silicones off. Sand all loose material until you get to a solid substrate. Prime bare metal with a good epoxy primer. A sealer or primer over the job makes for a better finish. Follow all directions on the product and I sand my primer with a bucket of water with a bit of TSP in it to keep everything clean. I have a car I painted in 1975 still in good condition.

[Gene F]

TSP ? Not all of us are experienced. Is this some kind of oil and grease remover spray they sell at body supply shop? What about a tack-cloth?

[J Franklin]

TSP: Tri sodium Phosphate. sold as a powder as a cleaning agent that is used before painting walls, and as a general cleaner. Hardware stores sell it. I mix it in water and use with my pressure washer outdoors and it is good when mopping the floors as it doesn't require rinsing. I rinse when washing cars.

[nkaminar]

The paint supplier will provide detailed instructions. Follow those instructions to the letter.

[Fordestes]

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Originally Posted by J Franklin

You need to sand after a thorough cleaning to get all oils and silicones off. Sand all loose material until you get to a solid substrate. Prime bare metal with a good epoxy primer. A sealer or primer over the job makes for a better finish. Follow all directions on the product and I sand my primer with a bucket of water with a bit of TSP in it to keep everything clean. I have a car I painted in 1975 still in good condition.

I didn't know to use water to sand primer, I am thinking epoxy, so use a surfacer over the epoxy ? is it a good practice to spray the under side fenders as well with the epoxy, I was concerned about it flaking from gravel etc. Thanks for the help.

[J Franklin]

Epoxy primer is tough. I prime bare metal with it on top and under fenders. I have painted the underside with Rustoleum and it has held up well. I don't waste expensive topcoat paint under fenders or on the chassis. I have 60 year old Rustoleum black on my model A chassis and it is still black and holding on. That is what you get with good prep work. Of course It has never seen salt and not a lot of inclement weather.

[nkaminar]

I painted the underside of my front fenders with the liquid Flex Seal. The rocks just bounce off.

[30Murray]

PPG has published some good guidelines on restoration. They have other more economical products than some of those listed but it gives you the general information. I used their Shop Line paints (JAU acrylic urethane) and was happy with the results. Their product data sheets will list what you can use under and over each type of paint. Follow this link:
https://www.ppg.com/en-US/refinish/s...toration-guide

[gdmn852]

Hello, before painting any bare steel, I use
Metal Prep , a mild acid that etches the steel for a good bond ,then use epoxy primer, always use proper respirator when using paint.

[Hitman]

You need to provide a lot more detail here. Are you blasting to bare metal, painting over older layers, what’s your budget, etc.

At a minimum, I’d follow the recommendations of the material manufacturer you intend to use. I wouldn’t follow much of what’s been said here including TSP and flex seal. The paints of the 70’s are nothing like what is used today.

[Fordestes]

Posted twice , sorry.

[Fordestes]

Originally Posted by Hitman

You need to provide a lot more detail here. Are you blasting to bare metal, painting over older layers, what’s your budget, etc.

At a minimum, I’d follow the recommendations of the material manufacturer you intend to use. I wouldn’t follow much of what’s been said here including TSP and flex seal. The paints of the 70’s are nothing like what is used today.

I still have flaking paint as I said iy don't have any primer under it and have not done any prep yet, this is the reason for the inquiry ,I don't want to start off wrong to begin with , I was thinking the flex seal too, But if you think it is a problem , I may pass and use regular under coating on top of the epoxy primer ,bare metal is what I am going for and don't want to re do it, I had forty years of no painting due to respiratory issues, I used Imron in the old days ,a while back I repainted a panel on my Lexus and I used o' reillys paint , it turned out Good , it seems like the paint went on a lot smoother and covered really well also it seemed a lot different than what we used years ago, hope it don't come off . I want a quality Paint , any suggestions on a good brand , I realize technology changes as often as the weather it seem like to me. what grit paper do I need to sand the epoxy before top coating , I can blast , sand or chemically remove the old paint, what is best? then use what grit paper before the epoxy on bare cleaned metal ? then use surfacer over the epoxy ,clean and sand with what grit paper? then top coat and finish sand ? is that what you recommend ? Budget is not a deciding factor at the moment , Thanks D r. Estes

[BRENT in 10-uh-C]

Originally Posted by Fordestes

I still have flaking paint as I said iy don't have any primer under it and have not done any prep yet, this is the reason for the inquiry ,I don't want to start off wrong to begin with , I was thinking the flex seal too, But if you think it is a problem , I may pass and use regular under coating on top of the epoxy primer ,bare metal is what I am going for and don't want to re do it, I had forty years of no painting due to respiratory issues, I used Imron in the old days ,a while back I repainted a panel on my Lexus and I used o' reillys paint , it turned out Good , it seems like the paint went on a lot smoother and covered really well also it seemed a lot different than what we used years ago, hope it don't come off . I want a quality Paint , any suggestions on a good brand , I realize technology changes as often as the weather it seem like to me. what grit paper do I need to sand the epoxy before top coating , I can blast , sand or chemically remove the old paint, what is best? then use what grit paper before the epoxy on bare cleaned metal ? then use surfacer over the epoxy ,clean and sand with what grit paper? then top coat and finish sand ? is that what you recommend ? Budget is not a deciding factor at the moment , Thanks D r. Estes

My thoughts are strictly an opinion and should carry no more weight than anyone else's, ....however I am kinda shuttering at some of these thoughts.



Allow me to offer some thoughts as I feel it applies to what your scenario is.

1st; When you say you have flaking paint, that throws a flag that substrates were improperly applied, -or omitted. The ONLY way to proceed IMHO is to remove all present paint & substrates and start with clean, bare metal.

2nd; TSP is generally frowned upon due to the salts minerals it has in its make-up. After applying, it must be thoroughly neutralized, -which requires copious amounts of water to remove all traces of the sodium. So, as one would imagine, flushing bare metal with water is not generally considered the best way to avoid rust from forming at a later time.

3rd; This next one definitely falls into 'your car / your methods' but the Flex Seal is not the way I would approach this. I tour with my cars on primitive roads and really do not have a rock chipping problem however I did the job correctly the first time. If the bottom side of the fender has been properly etched with media to provide a great mechanical bond, then a good quality 2K Epoxy Primer will provide great adhesion. If the bottom side of the fender does not need any fillers or high-build primers, then apply a good 2K Epoxy primer, allow it to flash dry and then proceed straight to the top-coat 2K Urethane of your choice. It is my opinion that you can spend time metalfinishing the sheetmetal repairs before the paint substrates are applied, -or you can spend the time (-and expenses) applying primers & fillers to cover the imperfections. If there are deep gouges or pitting, there are hi-build 2K Urethane Primers that are specifically made for DTM applications. Etching the metal by mediablasting is an extra step of assurance however sand is now frowned upon. Aluminum Oxide is my choice.

As Hitman stated below, paints have dramatically changed since I began restoring Model-As, -and especially in the last decade or so. You mentioned Imron above, ...and Axalta has reformulated and re-branded their Imron however we have found it has characteristics that are much different now than its forefather. After spraying PPG's DCC Concept for decades, PPG's single-stage products (Essential & Evolution) have fallen to the bottom of our preferred list with S/W Genesis and Axalta's Imron higher on the scale.

I will close by saying that I have found that most restorers applied WAY too many finish coats where the Mil thickness caused the paint to crack or chip. Modern vehicles can be driven on gravel roads without worry of paint damage simply because the Mil thickness is small from the factory. With modern paints, if you have a high-quality spray gun that will atomize the paint where it lays down without trapping air (-cause of orange peel), then applying one medium coat to act as a tack coat, allow enough time for it to completely flash followed by a heavy topcoat with slow solvents allows for minimum Mil thickness that generally flows out well. If you have complete coverage with two coats of paint, then go clean your gun and let it cure. I've listened to "experts" argue with me that they need to apply plenty of paint so they can colorsand and buff the paint. My argument is if you spray 4 coats but sand 2 - 2½ coats off to make it flat and smooth, then what have you gained?? Best wishes to you as you proceed.

[Richard Knight]

That is a lot of good and true info from Brent. I am not a painter or restorer but that doesn't mean I haven't painted some. I have painted nitrocellulose lacquer, acrylic lacquer, enamel, super enamel, color coat clear coat and most recent single stage urethane. When you paint infrequently and there are gaps of several years between paint work one thing I learned is that during the gaps everything changes. Every single time it is like starting over completely. What I did in the 60s, 70s, 80s, etc. have very little bearing on how you use the current paint products. I have a 29 A with some amazing original paint. I have a 30 coupe that was restored possibly in the 80s and it appears to be acrylic lacquer that has completely failed. Thousands of cracks, paint popped off, just a mess. For exactly the reason Brent said too much paint thickness. Whoever painted it seemed to think the more the merrier.it needs to be completely stripped. Most recently I restored a firewall loaded with bondo, brazing, welding and pushed in from an accident as far as I can tell . Fortunately I had the advice of a auto body shop owner. Completely strip to bare metal, do all metal work, epoxy primer, urethane primer, block sanding, a light coat of black sealer and TWO coats of single stage urethane. It was so hard to not put a third coat on but I was told TWO and that was the right thing to do. Hopefully this is somewhat helpful. Stick to one system of paint, read the instructions and get professional advice if possible. I used a hvlp gun and an old fashioned touch up gun. This was the easiest paint to spray ever for me

[Fordestes]

Originally Posted by Richard Knight

That is a lot of good and true info from Brent. I am not a painter or restorer but that doesn't mean I haven't painted some. I have painted nitrocellulose lacquer, acrylic lacquer, enamel, super enamel, color coat clear coat and most recent single stage urethane. When you paint infrequently and there are gaps of several years between paint work one thing I learned is that during the gaps everything changes. Every single time it is like starting over completely. What I did in the 60s, 70s, 80s, etc. have very little bearing on how you use the current paint products. I have a 29 A with some amazing original paint. I have a 30 coupe that was restored possibly in the 80s and it appears to be acrylic lacquer that has completely failed. Thousands of cracks, paint popped off, just a mess. For exactly the reason Brent said too much paint thickness. Whoever painted it seemed to think the more the merrier.it needs to be completely stripped. Most recently I restored a firewall loaded with bondo, brazing, welding and pushed in from an accident as far as I can tell . Fortunately I had the advice of a auto body shop owner. Completely strip to bare metal, do all metal work, epoxy primer, urethane primer, block sanding, a light coat of black sealer and TWO coats of single stage urethane. It was so hard to not put a third coat on but I was told TWO and that was the right thing to do. Hopefully this is somewhat helpful. Stick to one system of paint, read the instructions and get professional advice if possible. I used a hvlp gun and an old fashioned touch up gun. This was the easiest paint to spray ever for me

Thanks , I have gained a lot, AS I said it has ben a while , when I shot the panel on my Lexus It was the first time I ever used a H.V.L.P, Back when I only used a cup gun, so It was like starting over for me.I agree about too many coats may be a problem in the making .Thanks again.

[Fordestes]

Originally Posted by BRENT in 10-uh-C

My thoughts are strictly an opinion and should carry no more weight than anyone else's, ....however I am kinda shuttering at some of these thoughts.



Allow me to offer some thoughts as I feel it applies to what your scenario is.

1st; When you say you have flaking paint, that throws a flag that substrates were improperly applied, -or omitted. The ONLY way to proceed IMHO is to remove all present paint & substrates and start with clean, bare metal.

2nd; TSP is generally frowned upon due to the salts minerals it has in its make-up. After applying, it must be thoroughly neutralized, -which requires copious amounts of water to remove all traces of the sodium. So, as one would imagine, flushing bare metal with water is not generally considered the best way to avoid rust from forming at a later time.

3rd; This next one definitely falls into 'your car / your methods' but the Flex Seal is not the way I would approach this. I tour with my cars on primitive roads and really do not have a rock chipping problem however I did the job correctly the first time. If the bottom side of the fender has been properly etched with media to provide a great mechanical bond, then a good quality 2K Epoxy Primer will provide great adhesion. If the bottom side of the fender does not need any fillers or high-build primers, then apply a good 2K Epoxy primer, allow it to flash dry and then proceed straight to the top-coat 2K Urethane of your choice. It is my opinion that you can spend time metalfinishing the sheetmetal repairs before the paint substrates are applied, -or you can spend the time (-and expenses) applying primers & fillers to cover the imperfections. If there are deep gouges or pitting, there are hi-build 2K Urethane Primers that are specifically made for DTM applications. Etching the metal by mediablasting is an extra step of assurance however sand is now frowned upon. Aluminum Oxide is my choice.

As Hitman stated below, paints have dramatically changed since I began restoring Model-As, -and especially in the last decade or so. You mentioned Imron above, ...and Axalta has reformulated and re-branded their Imron however we have found it has characteristics that are much different now than its forefather. After spraying PPG's DCC Concept for decades, PPG's single-stage products (Essential & Evolution) have fallen to the bottom of our preferred list with S/W Genesis and Axalta's Imron higher on the scale.

I will close by saying that I have found that most restorers applied WAY too many finish coats where the Mil thickness caused the paint to crack or chip. Modern vehicles can be driven on gravel roads without worry of paint damage simply because the Mil thickness is small from the factory. With modern paints, if you have a high-quality spray gun that will atomize the paint where it lays down without trapping air (-cause of orange peel), then applying one medium coat to act as a tack coat, allow enough time for it to completely flash followed by a heavy topcoat with slow solvents allows for minimum Mil thickness that generally flows out well. If you have complete coverage with two coats of paint, then go clean your gun and let it cure. I've listened to "experts" argue with me that they need to apply plenty of paint so they can colorsand and buff the paint. My argument is if you spray 4 coats but sand 2 - 2½ coats off to make it flat and smooth, then what have you gained?? Best wishes to you as you proceed.

Thanks Brent , I hope I can make it shiny again, from what I have learned this car was used as a display piece for a business , the paint has no primer at all, and what I see it shouldn't be on the road till I get the mechanicals in order .I could read all the books in the world and cannot get an answer as good as what real world experiece has taught many . Thanks for sharing ,D.Estes

[BRENT in 10-uh-C]

Originally Posted by Fordestes

Thanks Brent , I hope I can make it shiny again, from what I have learned this car was used as a display piece for a business , the paint has no primer at all, and what I see it shouldn't be on the road till I get the mechanicals in order .I could read all the books in the world and cannot get an answer as good as what real world experiece has taught many . Thanks for sharing ,D.Estes

Yes, the advent of the Smart Phone and YouTube have almost ruined the concept of reasoning and common sense thinking.


What many do not understand is how paint technology has continually changed. IMHO, unless someone is exposed to this technology on a daily basis, what someone learned 6 months to a year ago is seemingly obsolete in today's world. Following advice from someone that is outdated or obsolete with today's products can get you into trouble very quickly, ...and at great expense.

While it is hard to wrap our heads around this sometimes, what we did 5+ years ago is often incorrect in today's work. For example, 10-15 years ago we use silica sand to sandblast Model-A sheetmetal. Because of the silica being imbedded into the metal where it caused contamination issues, we moved to mediablasting with glass. Now the manufacturers won't warranty unless the paint is stripped with plastic and followed with Aluminum Oxide. Next we can discuss fillers. In my early years, fillers (-i.e.: Bondo) were applied directly to the damaged areas of the sheetmetal. Do that today and the manufacturers will not warranty any adhesion issues ...which you likely will encounter. Today there is a difference between a Primer and a Surfacer. Most Primers are DTM whereas most Surfacers are not DTM however are designed to fill and be applied at a higher Mil thickness. How these are applied is different as is the type of spray gun that is used. In some materials, a spray gun is not used at all. Sandpaper technology is another thing that has changed. I could go on and on about things that I have seen changed during my restoration shop career, so my advice is that unless you are exposed to this craft on a daily basis, find someone who truly is and understands it. Likely this is not the O'Reillys A/P counter salesman.

[gdmn852]

Hello again, about new technology, I found that the newer type paint strippers are not to effective. I stripped the hood of 1949 Buick a few years back, paint came up in layers dryed up and easily scraped away. Recently bought some and was worthless! I guess they changed the formula as some one died ,didn’t read instructions about not using it in an enclosed place.

[Fordestes]

Originally Posted by gdmn852

Hello again, about new technology, I found that the newer type paint strippers are not to effective. I stripped the hood of 1949 Buick a few years back, paint came up in layers dryed up and easily scraped away. Recently bought some and was worthless! I guess they changed the formula as some one died ,didn’t read instructions about not using it in an enclosed place.

I agree, we used the aircraft stripper back 40 years ago ,I bought some in the spray cans and found the same results as you stated, I am thinking about using a vacuum blaster to remove some of the paint , I used to rent hem back in the early 80s from safety kleen to etch numbers in parts of my trucks, I blasted a mustang with one and it took forever but it done a good job . thanks for your input . D,R Estes