Inliners International Forums General Discussion Body & Paint Using POR 15

Has anyone ever had problems using POR 15 on the chassis? I used some semi gloss black last year on my frame and the whole bottom of the body and now like 70% of it is peeling off like a sticker. I never prep anything but they suggest painting over rust and all. I hate to re do it and do something wrong again. Please share any experiences you may have or if there's anything better.

I've had some peeling in places. POR15 is not as tough as I originally thought. Still a good product. I've heard that two extremely thin coats are best. That is purely heresay though.

I would say the best results are when the metal has been sandblasted clean and still has a texture. Scale rust MUST be removed before painting over any rust. Grease and dirt must also be removed.

I think (my opinion and not fact) that POR15 never really BONDS to the surface. It seems to only be a tough layer that seals out air and water so it prevents rust.

It should touch up pretty easy but I'd scuff the surfaces with 150 grit sandpaper first.

I recently bought a can of their competition - KBS Coatings - but have not tried it yet.

I avoid any product that claims 'little surface preparation needed'. Having said that I am happy with the results of POR products after I grind and wire brush the surface with an electric grinder and then wash off with a metal prep etchant and a final wipe down with a prep solvent. I'm a proponent of the "belts AND suspenders" school of thought.

POR15 web site has plenty of info on correct prep and application
if you want to check it out.

thanks for replying.

I'm watching this because I have a POR 15 kit and an engine ready to paint. The instructions list several steps and I'm lazy. In the long run it will most likely be better to do it by the rules the first time.

I did just that on my floor when I repaired it. No problems peeling a year later.

I had a couple of holes in the floor. Cut out the bad, welded in the good, seam sealed it, wire brushed the ENTIRE floor (scuffing where good, getting deep where scaley), coated the whole thing with POR and then put down a knock off to Dynamat. Everything is nice and solid.

On the bottom I followed pretty much the same process except instead of covering with Dynamat I shot it with undercoating. So far no problems there either.

On the area that is flaking: is it exposed to light? POR will fail under UV light.

[/quote]
POR will fail under UV light. [/quote]

I always topcoat POR15 for that reason.

I have been working with POR15 for several years now and agree with FTF - the zero prep angle is just not the case - especially if the metal in question is both rusty and oily . . .

In my experience POR15 likes a clean rough surface. Be it rusty (but with loose scale removed) or sandblasted - POR15 will grab it. POR15 is best when worked into the surface with a stiff brush. The clear version will make a rusty surface look wet. As it soaks in the rough grain begins to surface. Working in a second coat will return the wet look. I stop at two coats cause it is best to avoid build up. The topcoat (which can even be just primer) must be applied while POR15 is tacky - cause once it cures nothing sticks.

If the topcoat is the finish coat (which I prefer) it important to avoid POR15 build up and to time the topcoat. If the top coat is applied to early the POR15 will out-gas creating bubbles and substrate shrinkage. The best time to topcoat is when POR15 is sticky to the touch - but none of it sticks to your finger! As counter-intuitive as it may sound - cool and damp days are your friend when POR15 is your base. When it is beastly hot - clean and prep and wait for a rainy day.

Beater . . . for an engine block I prefer Glyptal Red as the base coat and an Engine enamel topcoat baked together.

Thank you everyone. I think I'm going to give it another try, but this time I'm going to prep everything well.

I'm a little late to the game, but I'd like to add a few things I learned about POR-15 in the last fear years. I have used it in the past, but now I switched to epoxy primers for various reasons.

1. You need to have a "binder" coat to topcoat POR-15, unless you use POR-15's topcoat (expensive)
2. If you don't, POR-15 can bubble up and peel right off the metal it's applied to.
3. It dries extremely hard. Part of being extremely hard is being NOT being extremely flexible.
4. I don't care who makes it or what it is, you want to start with a clean scuffed or etched surface.
5. POR-15 is not UV resistant and will break down with time if exposed to sunlight and not topcoated.

Alright, my reasons for those statements. I have used POR-15 on the floor pan of a 72 VW bug that we had blasted. Worked great.

I had some left over and, after noticing how well drips on concrete last, decided to pour it out onto a cement pad near the entry to our shop. Sure enough, it was hard as a rock after a few days and not coming off without, I thought, a chisel.

A few months later I was painting something and took my leftover mixed epoxy primer and tossed it onto before mentioned cement pad. Thought with enough leftover paint sessions it would be a neat looking chunk of cement, very modern art. Looked pretty cool.

Later yet, I had some mixed basecoat left over. Tossed it on, went to clear, had some leftover clear and went to throw it on the piece of art/concrete pad. However, all the POR-15 had bubbled anywhere the basecoat had touched it. Long story short, POR-15 really does not like UV reducer, which is why you need a binder coat if you want to topcoat it with any urethane product...so most any single stage or bc/cc paint.

After asking around on the forums as to why POR-15 has such a bad wrap in the professional world (you don't see it on high dollar builds unless they are sponsored) I learned a few things. POR-15 dries very hard, because of this when it's on panels or pieces that flex (about everything on a vehicle) it can develop micro-cracks that allow water to seep past. Hard to see with the naked eye but big enough to allow moisture through. Kind of like how something can rust if you paint it with no primer. Also, the very sales pitch and name of POR-15 (Paint Over Rust) is more or less a lie. People had coated old rusty fenders and, years later, scrapped it off to see what's underneath. The rust continued to grow, just under the POR-15. It is also extremely expensive and the formula,extremely cheap to make, is open for taking to any paint manufacture who wants to reproduce their own version, but no one does.. probably a sign?

All that being said, POR-15 will probably work just fine on properly prepared metal. However, epoxy primer will work just fine on properly prepared metal, is flexible, chip resistant, and able to be painted over without requiring extra steps. It's also easy to touch up and much less expensive. It can be thinned without special thinner and sprayed, brushed, or rolled just like POR-15.

Long story short, I'll stick with epoxy primer as it has every good point of POR-15 (except painting over rust, which just plain shouldn't be done) and fewer of the downsides. It is not expensive, requires no binder step, but is still not UV resistant and shouldn't be on external parts without a topcoat.

End Rant.

Mitch . . . I am not seeing any rant here whatsoever. Metal is inherently ductile in nature so there is no coating - Read NO COATING that will permanently prevent rust in ferrous metal subject to ebb and flow dynamics; which is in fact all metals subject to changes in temperature. Time is not on our side when it comes to steel and iron - and the time frame is shortened the more the metal is flexing.

I agree with your assessment on epoxy base coats - it is indeed the way to go with new metal or rust free metal. But in the restoration world totally rust free surfaces can be hard to come by. This is the niche of POR15. It reduces effort (labor) in preparation - but it doesn't eliminate it. Slathering POR15 onto loose rust scale will never take the place of mindful restoration with diligent preparation.

I also agree that POR15 is hard as nails. For this reason one needs to avoid build up especially in places where engineers intended ductile metal to be present - not rock hard polymers.

In the restoration world we need to work with all the technologies at hand. Non-Acid solutions like EvapoRust allow us to remove the majority of the iron-oxide from a rare part - without etching away good metal in an acid bath (as part of the prep). A thin coating of P0R15 provides rock hard water-proofing and sealing of missed rust or flash rust that appeared after the cleanup/prep step. A prep coat of epoxy based primer further readies the part for top coating . . .

In my mind it is not either/or . . . it sometimes one . . . sometimes the other . . . sometimes both . . .

regards,
stock49

Mitch/stock49, first of all let me thanks the both of you for the well explanations. Sound like you both been in this business a long longer than me. Maybe I don't need por15 after all. All I really want and I'm after is for the bottom of my frame, floors, suspension,etc to look cleaner and all black. I cleaned any surface rust there was. Now I just want everything to be black actually semi gloss. Does the only reason why I went with por15 in the first place, and because it can be applied by brush. I know I can shoot the whole thing with a gun but the car is already painted and I be afraid to get over sprayed. Is there anything out there maybe cheaper that I can applied by brush that will still work?

Either POR-15 or epoxy primer will work just fine for most of that. Neither is UV resistant, but you don't need UV resistance under a car. Both can be applied by a brush. You don't have rust, so you are OK there. Both will be semi-gloss black. I'm a big fan of SPI's epoxy, you can order from them or find a jobber near you. Here is a pickup frame I did with it, sprayed though.

http://c10forum.com/forum/showthread.php?t=14107&page=2

Mitch, can you send me a picture of the epoxy primer stuff? If it's cheaper I may go that route instead. Can I applied that stuff right now or should I spray down the whole bottom with a degreaser? And after that with a metal prep?

Interestingly enough, the silver POR-15 is better to put down first if you can. As for painting over rust, I just used it in some fairly inaccessible spots on the inner fenders, mostly because I am not in a position to take the front end apart and fully restore it so I had to use a few alternatives to address the rust. POR-15 was my choice over plain epoxy primer so I brushed it on and let it dry. Cleaned up the worst of the rusty parts and they look nice. Time will tell I suppose whether it is durable enough. Now on to top coating it with some semi gloss black. BTW, POR now has a product they call their "tye-coat" that can be shot directly over fully cured POR, as an adhesion coat to prevent lifting, bubbling all that stuff of the POR, and then top coated from that point, chassis black for me.

Brown Sugar, sorry for not reading your post sooner. I use Southern Polyurethanes epoxy. You can google the name and it'll pop up, give them a call, tell them what you are doing, and they will set you up. Great people.

Donohue, what information do you have on the silver POR-15 being better first? I'm always researching and would like to know how you arrived at that conclusion. Also, as far as the tye-coat goes, you can definitely go that route. However, by the time you add up the cost of the POR-15 and then add in another product (tye-coat) you are starting to spend some serious dough.

What it all comes down to is that I won't coat anything that is rusty in the first place. I don't take 1/2 measures if I can avoid them. I would rather spend the money and take the time to do it right once than to spend some money doing it "good enough for now" then spend more down the road doing it right. It definitely sucks doing it that way sometimes, but I have no worries in the back of my mind when it's finished. Everyone has their own ways, this is just mine. On clean bare metal, POR and epoxy will probably both work just fine. However, if you want to topcoat or get UV protection, it's more expensive with POR and your color selection is limited.