I’m going to strip a roof of rust this weekend. I need to protect it as the car will sit outside during the winter. Will epoxy primer withstand the rainy weather? Or do I need to spray paint over it? Also, some good stuff to use?
Not sure about weatherproofness, but I know that epoxy products tend to have poorer UV resistance than polyester alternatives. It might embrittle under harsh sunlight — I don't know how quickly, though.
With the cost of products these days it makes zero sense taking the risk and the problem is without taking the primer off again you can never be sure if it has started rusting underneath until it fails down the road. What's the point of do anything with it if it's going to sit outside all winter?
If you going to prepare it good enough for epoxy primer, get some colour, any colour in the product you will use eventually and hit it with that. You can block that down later and squirt over it. Most primers are not waterproof, they are water resistant and some are moisture absorbing.
I guess without know what it's like its hard to say what to do. If its a 50 plus year old car that has been rusting for it's whole life my thinking would be how much worse will it get over one more winter? Personally I would never take the chance of doing work over anything that has sat outside for a long period of time that didn't have a top coat on it designed to be exposed to the elements. Primers are not. Just way too much work and expense to have to redo something if it goes bad down the road.
If you have the panel prepared just as good as if you were ready to paint, 2 coats of epoxy will protect it for a while. The statement about epoxy not having uv protection is correct. The winter season has the least amount of uv rays. I recently painted a vehicle that had gone 6 months in epoxy before it was sanded and painted. It was indoors most of the time but exposed some. The epoxy sanded way better than when it's fresh. There were no signs of degradation. There were places that I sanded through and applied bondo. There was no sign of water leakage. I live in a semiarid area. If you live in an area where it is wet for months, I don't know if I would do it. To shoot a couple of coats of urethane over it could be very good insurance. I appreciate the comment about not having redos but that isn't a luxury that all get to enjoy.
Seems to me that rolling on a coat of Tractor Supply Implement oil base enamel would keep the weather out for a winter. Damn sight more protection for something outdoors than primer. My '46 Merc got a coat of house paint brushed on back in 1960 and it's still holding up.
I can't speak for the product you will choose to use, but here is 3 1/2 years of weathering wearing Epoxy Primer. That's a couple of winters, sun, wind and rain. That little bit of rust was an area a bit light on product.
The thing that I would be concerned about is making sure all surfaces had a sufficient coverage, top, sides edges etc.. Over the winter isn't going to hurt but over the winter can turn into ten years...
Once epoxy primer cures, it is very difficult to get paint to stick to it best to top coat within the window of about 24 to 48 hours for best adhesion Rustolilum will keep it sealed and stop the rust
If the intent is to start getting it cleaned up a bit, then protect it through the winter, so you have a head start on next spring. I'd cover it with some sprayed on Rust-oleum. What ever you cover it with this winter, you will likely sand off next spring. A gallon of Rust-oleum is $40, a gallon of epoxy is near $100 (both prices a couple months ago). The Rust-oleum will protect the metal better then the epoxy will over the winter if its sitting outside. If it ends up being longer then next spring, the Rust-oleum wins hands down longer term.
I always wonder in threads like this if all the guys who recommend procedures that no paint company would ever ok if they are going to donate their time and money to correct a problem if it happens down the road.
Not sure what brand ,but I am using Southern Polyreuthane epoxy and on their label it states the longer you leave it mixed in the pot before spraying the better the uv protection.
Add one-half part reducer to the epoxy and hardener, of the type that is appropriate for the brand/line. That will help close up the porosity of the primer, and add moisture resistance.
They have "winter" in California ? I agree with K13. Even if you do a good job protecting it, seems like something else always pops up that causes a problem. I just primered a raw steel body and then put some paint over the primer on the bottom of the body and inside the body. Left the rest in primer because it had to have something on it. It will sit inside a building though.......but even that will sometimes get colder than California.
Back in 1991 put on PPG DP 90 primer and still protected no rust bin in all types Weather Last photo current 2022
2006. Guess I was mistaken on when I sprayed these out. I guessed 3 and 1/2 years, more like 15 years. What's the best protection you ask. One that lasts. I'm not saying Rustoleum isn't a good product, just that for my needs Endura 2 part epoxy was money well spent. And while I'll have to scuff it down eventually, it won't be anything like the paper plugging power of Rustoleum stopping me.
DuPont 80S for the win! Car was sprayed in the early 80s, (with I think one re-spray possibly). She was never inside a garage and survived years exposed to the elements in N.J. The roof was shot at a later date with a different product that didn't hold up so well; it may have been POR-15. That said, it's currently undergoing a major re-do (yes, it's going down to bare metal before a new prime job) and will live in a garage.
SPI epoxy primer is one of the few that has UV inhibitors. https://www.southernpolyurethanes.com/epoxy-primer I've had a car in epoxy and dust for a long time, it's proven to be a very effective coating.
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