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Ok. I’ll start this by saying I’m not a professional painter in anyway. Don’t have any spray equipment and am pretty much at this point limited to rattle cans.

I can get a decent coat down but am having trouble getting the top coat to stick.

I’m re doing my son’s fast hitch for his cub. I blast everything and then prime it with this.



I can get this stuff to stick well and lay down very nicely.

The I hit it with this.


Can get it to go on well but even after drying for a few days it will just about scrape off with a fingernail. Not sure what I’m doing wrong. I’m. It standing between coats as the stuff I’m painting is cast and won’t be smooth anyhow. Shouldn’t it chemically ind to each other?

Any suggestions are appreciated.
 

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I would use an equipment primer in the same line as the farm color paint.

It is common to use a different solvent for the automotive vs the farm equipment. Example if I spray John Deere paint over a mineral spirits based primer it will soften the primer back up right to the metal. You might also try to paint at test piece as soon as the primer dries in 10 minutes or so. If the paint is incompatible it will wrinkle. You should never need to sand before using a farm enamel paint.


From the product page.
Prep your vehicle for a premium finish with Rust-Oleum® Stops Rust® Automotive Primer Spray. This heavy-duty base coat provides unmatched corrosion resistance and works beautifully with most brands of automotive
lacquers and enamels


From the equipment paint page. Paint and primer
Clean up wet paint with xylene or mineral spirits.

From the automotive paint
Wipe off tip when finished. Clean up wet paint with acetone or lacquer thinner. Properly discard empty container. Do not burn or place in home trash compactor.



The mineral spirit based farm enamel based paint should use the farm equipment primer. Even though the automotive and farm equipment paint are both enamels the automotive uses a stronger solvent.
 

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Leaving aside the two part epoxy paints, there are basically two types: lacquer and enamel.

Lacquers dry strictly by solvent evaporation. Think of a plastic dissolved in a solvent. Apply the mixture and when the solvent evaporates the plastic stays behind and hardens into a film. Lacquers are "cured" once the solvent is gone. Neat thing about them is that when you apply another coat or spray a repair area, the dried film is dissolved again by the new coat and the new coat bonds very well.

Enamels cure in two stages - solvent evaporation followed by polymerization. The solvent is a carrier that allows you to apply the mixture. Once the solvent evaporates, the film cures by linking monomer molecules into polymers. Without a catalyst or heat, this process can take several days. Once cured, it is no longer soluble in the original solvents. In order to get another coat to bond after curing you need to sand in order to create a gripping surface.

The Rust-Oleum primer you showed is an alkyd enamel primer and should be compatible with the topcoat. I prefer lacquer based primer surfacers as they dry more quickly and can be sanded immediately. They have better filling power then regular primer due to the very thick pigments used.

It sounds to me like your primer has not cured before applying your topcoat and that is the reason for the poor adhesion. Is it a fresh can or has it been sitting around for years (I still have rattle cans dating to the 1970s in my garage). Try priming a test piece and putting it under a heat lamp for 12 hours. Let it cool and apply a top coat. Give it the same heat lamp treatment and see the adhesion improves.

Al
 

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I used to do bodywork. Your problem is that your color coat is not adhering to the primer coat because the primer coat needs to be roughed up after it's dry. I like to use Scotch-Brite pads to sand the primer before adding my color coat. A fine sandpaper will also work, but the sanded primer tends to build up too quickly on the sandpaper.
 

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I agree. I used to paint commercially and it sounds like your top needs something to "bite" into. I would also suggest scuffing up the primer coat with a coarse pad and then top coat. Keep in mind any "spray paint" type application is going to be very weak and lack durability because it doesn't include a hardener. With all the HVLP/ DIY applications out there today, you'd be better off going that route if you have a compressor. No need to go crazy, some implement paint and a cheap-o harbor freight HVLP sprayer is really all you need.
 

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I agree with the other two.

You either need to be recoating within the required time frame when spraying like paints (primer or topcoat), or once its dry and past that time, you need to scuff it slightly to get the next coat to adhere.
You could use the best primer in the world, but if you dont scuff it first, nothing will stick well.

Also make sure the paints are compatible.
Sometimes tractor and implement paint is oil based, and it needs a proper compatible primer. Well, any paint does, but they are specific to the type of paint.

I also agree about the spray method.
Spray paint is pretty darn expensive comparatively. Now if you cant do it, you cant do it, but if you already have a compressor, its not that hard to do.
Cleanup can be a bit messy if you arent used to it, but even then, you end up with a better overall finish, even with a cheapie spray gun.
 
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