Painting with automotive paint without primer?

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Creative25
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Painting with automotive paint without primer?

Post by Creative25 »

In our area we don’t have that many options for paint.
Specially if you want a certain color.

Options we have is those.
PVA
Oil paint
Car paint medium quality

I prefer the automotive paint.
We don’t have much rust problems because we live in a very dry area.

My question I this.

If I paint some letters etc that will be indoors
Do I need to use primer or can I paint them directly?
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Joe Jones
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Re: Painting with automotive paint without primer?

Post by Joe Jones »

Rust is a process of moisture interacting with ferrous metal. If the metal you are painting has any moisture on the surface, and you trap that moisture beneath a layer of paint, it will rust. You can try to HEAT the metal before spraying it with automotive paint. Not screaming hot. Just enough to cause water vapor to evaporate off of the metal before the paint is applied.

However, I think a layer of primer is a really good idea, anyway.

Joe
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adbuch
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Re: Painting with automotive paint without primer?

Post by adbuch »

Hi Ueli - you don't necessarily need to apply primer to the metal before using the automotive paint. Just make sure the metal is clean with no oil or rust. For indoor use - you should be fine. For best adhesion of the paint to the metal, you would do well to sand the metal surface first with medium sand paper (150 to 220 grit) and clean it well afterwards.

While you are at it - you can do a test and paint a test piece with no primer and leave it outside to see how it lasts.

David
Creative25
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Re: Painting with automotive paint without primer?

Post by Creative25 »

I found automotive primer to be notoriously rough on the surface. With small inside shapes that would be lots of work to sand the inside. Would red oxide work ok for aoutomotive paint?

I just made this as a gift.
IMG_0832.jpeg

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adbuch
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Re: Painting with automotive paint without primer?

Post by adbuch »

I think that looks good! Sort of like a hammered finish. There are two main varieties of automotive primer - primer surfacer is meant to be sanded, where as bare metal primer is not. I have used both types when painting cars. Normally red oxide primer is more for bare metal and not necessarily meant to be sanded. Also - the primers I use are normally catalyzed with a hardener before spraying. Same for the paint I use. For single stage automotive paint - my favorite is catalyzed acrylic enamel. It flows out nicely if you use the correct reducer, and can be optionally sanded and buffed if you desire a smooth mirror like finish.

Here is a car I painted with catalyzed acrylic enamel. The body was stripped to bare metal and then primed, painted, and color sanded/polished.

David
914.jpg

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Creative25
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Re: Painting with automotive paint without primer?

Post by Creative25 »

I did some automotive painting as well fixing dents on my cars etc.
Our rural areas.
Most places only sell 2 k primer and 2k paint
Except for metallic base coat.

That sign is my first time I used metallic paint.


I just think doing the same prep for a sign as you would for a car is overkill.
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