Paint question..sealer

[Doc Corey]

OK, I took the advice of some on here and removed the edp coating on my new fenders, and sure enough, there were some minor pits in the metal with rust growing in them. My question is , what is the best primer or sealer to spray these bare fenders with. I need to coat them before they flash rust, then do some minor smoothing and filling a few flaws. If it makes any difference, my final paint will be acrylic enamel likely Lemon Twist or Lime Green. I did go online to look for answers, but it turns into a mess trying to decipher a good answer from all the commercial spam.

 

[Adam]

You should use an epoxy primer on clean bare metal. Epoxy primer is very tough and non porous. You can do body work on top of the epoxy. A sprayed panel can sit for years, indoors, and just scuff & top coat. But epoxy is not easy to sand, So most often it is top coated with a 2k polyester filler primer (2k means two parts, primer and hardener). Poly, filler, surfacer, primer refers to a thick primer that has a hardener in it. It is used to fill minor scratches and imperfections. You lay it on thick (2-3 coats for a problem area) and it will chemically harden. These primers are easy to sand and can be top coated with just about anything after they are fully cured.

Filler primers, etc., are for the exterior of the car. You will need to wet sand the filler primer using 400 or 500 wet-dry and a sanding pad. Coarser than 400 may show scratches/ 600 is too fine and you may have adhesion problems. I use a bucket of warm water (easy on the hands) and a rag to wipe the area with. Rinse the sand paper often. As you sand you will feel the primer go from rough to smooth in just a few strokes.

Some people use a sealer primer after. This is basically to get the car all one color (because primer can/does effect the color coat) and to ensure there is no chemical reactions between the color coat and the base coat. This really only happens when shooting over old original style paint, lacquer and such. Any hardened primer, epoxy and filler) is compatible with any modern paint; acrylic enamel is good over all these primers. You don’t need a sealer unless you have these issues.

Some old school guys use a glazing compound to fill scratches, pin holes, and other imperfections. The old glazing compounds did not have a hardener and would lift when the reducer in the top coat got to it. The newer glazing compounds have a hardener and do not need to have a sealer over them.

This is why paint jobs can cost so much, even with no body work, you likely need an epoxy coat, a poly coat, then color coat, and maybe a clear coat on top.

3M Wetordry Sponge Pad No. 20 - 05526

Firm hand sanding pad to be used with a three-fold wrap of 3M silicon carbide paper sheets, Wetordry Color Sanding Paper Sheets or Production Gold Paper Sheets to make hand sanding easier and more efficient. 2-3/4 in x 5-1/2 in x 3/8 in pad size 1 sponge pad

www.autobodytoolmart.com

 

[Adam]

If you do get flash rust you can clean it with ospho and a green scotch brite pad. Ospho leaves a sticky residue, so I dilute the ospho by about half for the first treatment. For the second treatment I dilute it to about 90% water & 10% ospho. Wipe it on and wipe it off. Ospho directions say to use it straight, leave it on, and paint over it. Maybe on really rusty farm equipment… but not on your cars exterior.

They sell Ospho at Home Depot and Walmart.

 

[Doc Corey]

You should use an epoxy primer on clean bare metal. Epoxy primer is very tough and non porous. You can do body work on top of the epoxy. A sprayed panel can sit for years, indoors, and just scuff & top coat. But epoxy is not easy to sand, So most often it is top coated with a 2k polyester filler primer (2k means two parts, primer and hardener). Poly, filler, surfacer, primer refers to a thick primer that has a hardener in it. It is used to fill minor scratches and imperfections. You lay it on thick (2-3 coats for a problem area) and it will chemically harden. These primers are easy to sand and can be top coated with just about anything after they are fully cured.

Filler primers, etc., are for the exterior of the car. You will need to wet sand the filler primer using 400 or 500 wet-dry and a sanding pad. Coarser than 400 may show scratches/ 600 is too fine and you may have adhesion problems. I use a bucket of warm water (easy on the hands) and a rag to wipe the area with. Rinse the sand paper often. As you sand you will feel the primer go from rough to smooth in just a few strokes.

Some people use a sealer primer after. This is basically to get the car all one color (because primer can/does effect the color coat) and to ensure there is no chemical reactions between the color coat and the base coat. This really only happens when shooting over old original style paint, lacquer and such. Any hardened primer, epoxy and filler) is compatible with any modern paint; acrylic enamel is good over all these primers. You don’t need a sealer unless you have these issues.

Some old school guys use a glazing compound to fill scratches, pin holes, and other imperfections. The old glazing compounds did not have a hardener and would lift when the reducer in the top coat got to it. The newer glazing compounds have a hardener and do not need to have a sealer over them.

This is why paint jobs can cost so much, even with no body work, you likely need an epoxy coat, a poly coat, then color coat, and maybe a clear coat on top.

3M Wetordry Sponge Pad No. 20 - 05526

Firm hand sanding pad to be used with a three-fold wrap of 3M silicon carbide paper sheets, Wetordry Color Sanding Paper Sheets or Production Gold Paper Sheets to make hand sanding easier and more efficient. 2-3/4 in x 5-1/2 in x 3/8 in pad size 1 sponge pad

www.autobodytoolmart.com

Thanks!

 

[Doc Corey]

You should use an epoxy primer on clean bare metal. Epoxy primer is very tough and non porous. You can do body work on top of the epoxy. A sprayed panel can sit for years, indoors, and just scuff & top coat. But epoxy is not easy to sand, So most often it is top coated with a 2k polyester filler primer (2k means two parts, primer and hardener). Poly, filler, surfacer, primer refers to a thick primer that has a hardener in it. It is used to fill minor scratches and imperfections. You lay it on thick (2-3 coats for a problem area) and it will chemically harden. These primers are easy to sand and can be top coated with just about anything after they are fully cured.

Filler primers, etc., are for the exterior of the car. You will need to wet sand the filler primer using 400 or 500 wet-dry and a sanding pad. Coarser than 400 may show scratches/ 600 is too fine and you may have adhesion problems. I use a bucket of warm water (easy on the hands) and a rag to wipe the area with. Rinse the sand paper often. As you sand you will feel the primer go from rough to smooth in just a few strokes.

Some people use a sealer primer after. This is basically to get the car all one color (because primer can/does effect the color coat) and to ensure there is no chemical reactions between the color coat and the base coat. This really only happens when shooting over old original style paint, lacquer and such. Any hardened primer, epoxy and filler) is compatible with any modern paint; acrylic enamel is good over all these primers. You don’t need a sealer unless you have these issues.

Some old school guys use a glazing compound to fill scratches, pin holes, and other imperfections. The old glazing compounds did not have a hardener and would lift when the reducer in the top coat got to it. The newer glazing compounds have a hardener and do not need to have a sealer over them.

This is why paint jobs can cost so much, even with no body work, you likely need an epoxy coat, a poly coat, then color coat, and maybe a clear coat on top.

3M Wetordry Sponge Pad No. 20 - 05526

Firm hand sanding pad to be used with a three-fold wrap of 3M silicon carbide paper sheets, Wetordry Color Sanding Paper Sheets or Production Gold Paper Sheets to make hand sanding easier and more efficient. 2-3/4 in x 5-1/2 in x 3/8 in pad size 1 sponge pad

www.autobodytoolmart.com

Oh, the problem I have with the published instructions of several makers' epoxy-primer coats regards the 'non-sanding' or 'sanding'. Some describe that they (non-sanding) must be top-coated with something within a specific period, or encounter bonding issues. They do not go further to describe scuffing with some grade of abrasive if you wait for weeks or months. I suppose the less they tell you, the less liability they incurr. I get that. Then, there's that confusing 'primer-sealer' class.........

 

[Doc Corey]

Oh, the problem I have with the published instructions of several makers' epoxy-primer coats regards the 'non-sanding' or 'sanding'. Some describe that they (non-sanding) must be top-coated with something within a specific period, or encounter bonding issues. They do not go further to describe scuffing with some grade of abrasive if you wait for weeks or months. I suppose the less they tell you, the less liability they incurr. I get that. Then, there's that confusing 'primer-sealer' class.........

One more thing, about the color of the primer, best suited to either the Lemon Twist or Lime?

 

[Challenger RTA]

SEM rust mort. Do it first. I should have bought a gallon.in the long run would have been cheaper.Then apply USC SPRAY MAX 2K EPOXY RUST CURE PRIMER 3680032 AEROSOL SPRAY CAN Spraymax. best way to buy as you prep areas. once you activate you have to use it! If you spay a thin coat just to cover, it will be a sealer.. then when ready scuff and recoat for build up if needed. someone else my like a different product.

 

[Adam]

I would use a light colored primer for light colored paints and vise versa….

Btw, Transtar speed sealer is ready to shoot out of the can; it is thin and lays down flat, very forgiving. No sanding required. But it is best used over a catalyzed primer, or cured paint.

 

[brotow]

What does 2K mean in paint?


Two-component paints (also referred to as 2K paints) are paints in which a chemical reaction results in paint hardening. Hardeners for two-component paints are usually polyisocyanates that combine with the base paint to form very durable coatings.