Urethane Primer On Rusto Primer Test OT

[55 Fargo]

Hi all, I bought a high build urethane primer/surfacer yesterday. I was concerned about using it over Rusto pirmer, which is really alkyd/oil based primer.

No issues whatsoever with urethane over the rusto primer, in fact I have been using body filler and fibregalss resin over it too, no issues with adhesion/ wrinkling or peeling.

So far so good, if I was to do this over again, I might prime over the bare metal with 2 k epoxy primer, it is reasonably priced for the more economical brands.

I still think the rust primer doctored with reducer, is a great substrate/initial primer, it has great adhesion, and corrosion protection, as does epoxy primer, but a 2 k epoxy primer has fantastic corrosion/water resistant properties.

So far so good, plan to topcoat with acrylic enamel.........................Fred

[wilmot andy]

I am spraying my truck with SPI epoxy primer. I had sprayed my running boards a year ago with rustoleum, and saw that paint would not hold up, softer and was already scratching. I sprayed the epoxy over the rustoleum after I scuffed and sanded it. The finish is all 'crinkled'. I knew I would have to take it all down to bare metal again, or will have adhesion problems.

[55 Fargo]

That has never happened to me using this type of primer, maybe the paint is different, I als never had the paint/primer stay soft, once hardner was included.

I think for some reason the Rutoleum you had on the running boards may have never fully cured, that would cause a problem like this.

I have used fibreglass resin, bondo, now urethane products, on the fully cured ruso primer, never an issue to date. I know another on this forum who uses filler, and lacquer based priomer surfacer, and acrylic enamel topcoats over ruto primer, with neve na adhesion problem.

2 K Primers, can be different though, so as you say your best to strip to metal and shoot on the epxoy.......Fred

[Norm's Coupe]

Due to the solvents used in certain paints and coatings it's not always possible to coat over them with another product.

Example: If you use a product like Rustoleum or other rust type paint, then go over it with a solvent based urethane or epoxy it could cause the problem Wilmont Andy had. That's because the solvent in the urethane or epoxy paint is a stronger/different type than what is used in the rust type paint. Sometimes you'll get the reaction right away with it crinkling like he had, or sometimes it will take awhile and you'll start to see alligator cracking in the paint. That's because the paint on the bottom is softer and as it continues to dry out, it shrinks causing the top coating to also alligator/crack.

It's the same principle that applies to roof coatings. I'm sure many of you have heard you cannot put asphalt roof coatings over a roof that has been coated with a tar coating. That's because the tar coating stays softer longer and moves more than the asphalt does. So.........if you do that the roof will alligator within about a year (or faster) if you apply the asphalt coating over the tar coating.

Taking that one step further you can do it in reverse, apply the tar over the asphalt without a problem.

The same applies to epoxy and urethane products, unless that particular urethane or epoxy product is designed to go over the softer material.

So........the bottom line here is, you have to watch which products are compatible to one another. Best way to do that is with the paint supplier.

The only other way to go over a softer paint/coating with a harder one is to make sure the softer product is so dried out that it will no longer react from the solvents of the harder paint/coating.

[55 Fargo]

The 2 K Urethane primer/surfacer, is compatible with the following, it can be applied over , all sanded clean OEM finishes whether there enamel or urethane, 2 k epoxy primer, etch primers, all body fillers and putties.

As I have mentioned before, there is an individual that uses Rustoleum Primer, as a base primer,on bare steel. He then uses auto grade lacquer based primer/surfacer, with filler and putty, to date he has done several cars, with no ill effects to the 1 st base coat Rust primer, no paint has fallen off or wrinkled etc.

The cars he has painted are topcoated with single stage acrylic enamels.

There are some high end resto shops in the USA, that use plain old Rustoleum primer,as a 1st base on very expensive classic car restos.

I will agree with follow the directions of a manufacturers paint system, as it would yield the best results, but unless you are a trained professional, ie, you work in the industry, and have been trained by say PPG on the use of there product lines, you as a backyard painter, may not be privy to the manufacturers warranty.

I have personally used the rust primer on my car, it was reduced with Medium Speed acyrlic enamel reducer, 3 coats wet-on wet. To date I have also put over this primer, bondo filler, fibreglass filler, fibreglass resin. These products are very strong , they did not phase the rust primer, this primer is not soft, it is hard as rock.

I recently painted some heat registers, I used white rust rattle can paint, this paint is over a month on the registers, it is still soft, that is because I did not doctor there formula, with hardener or reducer, that paint would no doubt have troubles with adhesion and compatibility with other paint type.

Whatever works, works, not everything does mind you, the guy who gave me the rusto primer idea, I respect and value his judgement, he has a proven track record working with these products..........Fred

[Johnny230]

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Edited December 31, 2021 by Johnny230

[JoelOkie]

Strictly "for what it's worth".......This paint on this 46 Ford truck is made up of 2 coats of rustoleum rusty metal primer on all surfaces (while the truck was torn down, to insure edges were well covered), then rcovered by 2 coats Crossfire 2k filler/primer, then the truck was reassembled and covered by 2 coats regular lacquer based primer (inexpensive HighBuild brand from O'Reilly's that sands very fast, and gets very smooth quick), then top coated with 2 coats NASON enamel. It has stayed better overall than any paint job I have done up till now. There is absolutely no crackling/bubbling/peeling/blisters ect. issues anywhere. I have no idea if this is supposed to "work", or not, but 5 years in to this, this truck still looks pretty nice. Joel

[Norm's Coupe]

Strictly "for what it's worth".......This paint on this 46 Ford truck is made up of 2 coats of rustoleum rusty metal primer on all surfaces (while the truck was torn down, to insure edges were well covered), then rcovered by 2 coats Crossfire 2k filler/primer, then the truck was reassembled and covered by 2 coats regular lacquer based primer (inexpensive HighBuild brand from O'Reilly's that sands very fast, and gets very smooth quick), then top coated with 2 coats NASON enamel. It has stayed better overall than any paint job I have done up till now. There is absolutely no crackling/bubbling/peeling/blisters ect. issues anywhere. I have no idea if this is supposed to "work", or not, but 5 years in to this, this truck still looks pretty nice. Joel

Nice looking truck.

[55 Fargo]

Strictly "for what it's worth".......This paint on this 46 Ford truck is made up of 2 coats of rustoleum rusty metal primer on all surfaces (while the truck was torn down, to insure edges were well covered), then rcovered by 2 coats Crossfire 2k filler/primer, then the truck was reassembled and covered by 2 coats regular lacquer based primer (inexpensive HighBuild brand from O'Reilly's that sands very fast, and gets very smooth quick), then top coated with 2 coats NASON enamel. It has stayed better overall than any paint job I have done up till now. There is absolutely no crackling/bubbling/peeling/blisters ect. issues anywhere. I have no idea if this is supposed to "work", or not, but 5 years in to this, this truck still looks pretty nice. Joel

Thanx Joel, so using bondo fillers/fibreglass resins, 2 k urethane or epoxy primers, lacquer based primer, acrylic enamel or urethane paint should be fine over rusto primer?

I have done most of these things to date,on my rustoleum type metal primer on my car, so far no problem, hopefully there is no problem.

I am going to PM you, I have some filler questions, if you don't mind? Will do this later today, or might email you..........Thanx Fred ps luv the Truck, hope to see it someday

[JoelOkie]

Thanks Norm. I have enjoyed this truck.

Fred, I have put body filler directly over both the rustoleum primer, and, also, after blocking in the filler primer, in regard to finding and filling low spots. Mostly after the filler/primer coat, though. I don't sand the rustoleum, so don't usually find the lows until after the filler/primer. No problems thus far, as to body filler sticking to anything. I don't typically have too deep of a low to fill, so the body filler is not thick. I have not used any glass filler.

I am not sure that it would make any difference, but I have always applied the 2k filler/primer directly over the rustoleum primer, then the other primer/paint applications over the 2k.

Being in the building/remodel trade for many years has afforded me a pretty good working knowledge of the mechanics of painting, I am just not schooled enough in the science of various paints, like Norm, and some of the others on the forum. I know that what he is saying about how the various coating's own particular solvent, or vehicle, used in that particular paint could be in conflict with the chemistry of the previous coatings, or what it will be topcoated with, ect, makes sense. I have not encountered this at all in the method I have used, but would hate to steer anyone in the wrong direction, but I don't think that you would have to wait too long to know if something is going to work, or not.

I'll look forward to hearing from you soon, Fred.

Joel

[Norm's Coupe]

Joel,

Even though I said what I did, it's not all black and white either. I play around with this stuff all the time trying different things. Even things that aren't supposed to work, just to see why it doesn't work. Like with our epoxy flooring. Several years back I mixed one of our epoxies with something that was a total no-no according to all that was printed about you should not do it. I could see nothing harmful health/safety reason about using an additive that it said not to. So........I did it anyway. Well..........it worked just fine as far as doing the job it should do, and even better than expected. Only problem was the color of the finished product that couldn't be changed. Was a real ugly green, like a rotten color. So........that's been shelved ever since.

But the point is, nothing ventured, nothing gained. I've been playing around with various things like that for 40 years. Some turned out good, and others not so good. So.....the same applies to what you guys are talking about with using various paints/primers.

[55 Fargo]

Hi all, worked the outer trunk lid, 3 coats of filler, then a skim coat. The trouble then began, for some reason skim coat does not want to dry, 3 hours later, it is set, but not cured hard, every bit of sand paper was clogging, planned to finish the skim coat, with 120 then 180, then shoot on 2 coats of primer surfacer.

I had to end up using 80 grit, but it dug in a bit leaving me with some scratching, it was getting hardened, but the scratches were there.

Now either I did not use enough cream hardener, or the humidity level was too high, or both.

I shot on the primer, sprays real nice, but man is this stuff ever strong, yes I was wearing an MSA respirator mask, garage doors up a bit.

The primer looks great, my filler work on the panel looks good, but the scratches are still there.

I will have to sand down the trunk lid, try and get out the scratches, then shoot on 2 to 3 coats of the urethane high build, and hope for the best, and/or use some 2 k putty.

Now this a learning experience, I did my spray gun clean-up with lacquer thinner, man that stuff is awful too, the HVLP gravity feed gun, leaves very little overspray thank God.....................Fred PS the 2 k urethane primer and body filler went over the alkyd oil based rusty metal primer no problem

[Plymouthy Adams]

odds are you were a bit lite in amount of cream hardener...sure makes for a mess I assure you..I have done this before..I normally use the blue tinted hardener instead of the red for I can see the blue better...let this primer set up good...sand with 120 Norton gold...will lay smooth..then shoot some primer surfacer..should go a long way covering the scratches...

[55 Fargo]

odds are you were a bit lite in amount of cream hardener...sure makes for a mess I assure you..I have done this before..I normally use the blue tinted hardener instead of the red for I can see the blue better...let this primer set up good...sand with 120 Norton gold...will lay smooth..then shoot some primer surfacer..should go a long way covering the scratches...

Thanx Tim, I like Norton paper, it seems better than some of the others, my Local Wallyworld has it.

This primer can be used as highbuild, just use without adding any extra reducer, only hardener and primer, now if I could learn to pour out of a full gallon without being sloppy, any suggestion, what do you use for mixing and measuring devices.

[Plymouthy Adams]

I bought a very nice large Pyrex measuring cup..easy clean up might I add..I also cut the front off a rectangular gallon reducer can..this makes for ease of clean up and you can easily our off the cleaning solvent into another container for reuse.. cut so the screw top is at the top edge...I recycle this stuff till there is nothing left to recycle..cover and let stand..heavy stuff settles, carefully pour off the good stuff..wipe out the residue with a rag/paper towels..