To POR-15 or not, that is the question

[Rusty Jones]

So, after watching my brother struggle , and ultimately loose the battle, with POR-15 and his 87 BMW 325i I vowed to never use the stuff. I personally saw him prep the floor interior, and ultimately watch it peel up in large chunks. The paint was hard as a rock, no flex at all. Does this product have any redeeming qualities?

RJ

 

[Master Hack]

Never used the stuff. Thick rust encapsulator paint? Flex seal?

 

[67DropTop]

I've used it and have had only good results. It's on parts of my Mustang that was applied more than 20 years ago and there is no bubbling or peeling. Note: I've only used it on prepped metal. There are other moisture-cured urethanes, but I like POR-15 because it comes in little cans.

 

[MyFirstCar66]

When the stuff is correctly applied to surfaces as intended, it's damn near impossible for it to come up. If it is in places that can be exposed to UV / sunlight, it HAS to be topcoated... that said, I used some to coat and level a pitted floor in a car and to coat the inside of a solid but flashed cowl. Some of it spilled on my carport floor. It has been run over thousands of times, flooded, pressure washed, chemicals spilled on it, swept and rolling jack pushed over. That was seven years ago and that stuff hasn't budged.

 

[Jim Herrud]

I used gray POR-15 on the underside of my '65 Fastback way back in 2005 in the middle of this 33-year restoration odyssey. Since the car's still not done, I can't say that the surface has been tested, other than with time. With what I've learned in the intervening years about POR-15, I might make a different decision today. That said, after 21 years, I think it still does look really good:

 

[67DropTop]

It looks like you sprayed it last week. With the super glossy surface, that's what I've experienced as well.

 

[Jonk67]

I used POR15 - 8+ years ago on my lower firewall toe board inside (under brake/gas pedals down to seam), used the required cleaner, etc. followed the can rules and it seemed to be rock hard and a good surface cover but now I've decided to cut the drivers floorboard out and weld in new metal due to some pitting in the floorboards. As I started cutting I had to remove some of the POR15, it peeled up in sheets with some of the metal surface rusting under it. The car has been garaged for 10+ years during rebuild.

I've since switched to MasterCoat metal prep and the Silver + a top coat for UV protection. Looks like they're on vacation right now as they're a mom & pop (or daughter actually) business.

This stuff has been working amazing for me, I soak rusty nuts, bolts, brackets, etc. in it for 15 min. and then dip them in trans fluid and dry. I've used it on boat dock 40' gangway, JD mower undercarriage, Mustang, etc. so far it's holding up excellent. Lizer (scientist) on VMF personally tested and knows the manufacturer and reviewed it often.

 

[money pits fixer]

When the stuff is correctly applied to surfaces as intended, it's damn near impossible for it to come up. If it is in places that can be exposed to UV / sunlight, it HAS to be topcoated... that said, I used some to coat and level a pitted floor in a car and to coat the inside of a solid but flashed cowl. Some of it spilled on my carport floor. It has been run over thousands of times, flooded, pressure washed, chemicals spilled on it, swept and rolling jack pushed over. That was seven years ago and that stuff hasn't budged.

You get it on you ,its wear it off. I'll have to look in my cowl & see if the fix useing por 15 is holding up after 6 or 7 years now.

When the stuff is correctly applied to surfaces as intended, it's damn near impossible for it to come up. If it is in places that can be exposed to UV / sunlight, it HAS to be topcoated... that said, I used some to coat and level a pitted floor in a car and to coat the inside of a solid but flashed cowl. Some of it spilled on my carport floor. It has been run over thousands of times, flooded, pressure washed, chemicals spilled on it, swept and rolling jack pushed over. That was seven years ago and that stuff hasn't budged.

 

[bartl]

Not a fan, especially not a fan of painting over rust. If there's any practical reason for painting over rust then I first "neutralize" the rust by converting the ferrous oxide (rust) into inert ferrous phosphate using a phosphoric acid solution, removing the rust using a chelating agent (eg. EvapoRust) or via an electrolysis bath (works great on items like doors, hoods and trunk lids, especially as it gets into all the "nooks and crannies, seams, etc.). If there's any residue remaining and after the area is THOROUGHLY DRY, an application of an Epoxy Primer or a Moisture-cured Urethane (eg. Mastercoat Master Series Silver) is applied in the hope that the area is now completely sealed and impervious to the two things that will cause rust.... moisure and oxygen. My recommendations are based on the number of negative comments I've read over the last 25 or so years on each product..... you rarely hear of people relating negative issues with using Master Series.....