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Por-15 or Rustoleum


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There is a thread somewhere on this forum , may be about 3 years ago, there was  exhaustive comments. One fellow even emailed me about the negative experience he had. He was from South US. He was afraid of being sued if he went public. Any how he said he painted his frame and left in the garage for a year. When he looked, what seemed like dust was not dust. He bew the "dust" away . It was the POR paint  I never used it. One thing for sure is if and when you decide to remove it  will be hell . I acid dipped my running boards , primed with etching primer and used Rustoleum.

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I feel Por 15 is a top coat.  I would prime and paint as suggested by trini.  Then wipe it with fine steel wool just to lightly roughen the surface.  Then apply Por 15. 

Por 15 is a rubberized coating.  If you do not give it a good surface prep, it will peel right off like latex paint. 

Also, I have never been real fond of rustoleum.  It seems like more of an oil based paint.  My preference is 2 part epoxy primer and then acrylic enamel paint.  That is what all the body shops will use on bare steel.  The Por 15 will provide some protection from rock chips as it has a little flex in it.  

Hugh 

Edited by Hubert_25-25 (see edit history)
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If I remember correctly the instruction on the Por 15 can says it is best to paint on rust. It needs the rust to react chemically in order to be effective. What puzzles me is this product has been around the flea markets for a long time and has yet to be accepted fully by the restorers. Is it snake oil?

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Seems like there is a lot of misinformation on what POR 15 actually is.   First it does not react to rust, it dries in the presence of moisture and forms a seal to keep the ingredients needed for metal deterioration to continue. Effectively moisture is a catalyst similar to how a two part automotive Urethane works.  It is far superior at holding out moisture than a single part primer and Rust-Oleum the same that a modern two part urethane paint is far superior to an old air dry enamel.  One note.  POR 15 contains iso- cyonates.  You need to use a respirator when using with plenty of ventilation and should use a supplied air type.  I spray por 15 after properly prepping the metal, just like any other paint product. The final product is only as good as the prep.

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GM has been using something on bed liners recently but it is definitely not Por 15. The Por 15 I have seen is a thick stuff. stuff. I cannot see how a paint spray can work . I used  a paint brush and no cleaner will wash the brush. May be I am missing something.

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8 hours ago, trini said:

If I remember correctly the instruction on the Por 15 can says it is best to paint on rust. It needs the rust to react chemically in order to be effective. What puzzles me is this product has been around the flea markets for a long time and has yet to be accepted fully by the restorers. Is it snake oil?

 

POR-15 doesn't "react" with the rust, it needs the roughness of the surface to grip. If you apply it to clean, shiny metal, it will not stick. Even sandblasted metal isn't ideal, although it's pretty good. POR-15 has fantastic sheet strength but relatively poor adhesion, which is why it's called "paint over rust." Apply it wrong or to the wrong surface, and it'll fail. Give it something rough to hold on to and it will never come off. If you apply it over primer or paint, it'll fall off. It doesn't need any kind of chemical bond, so primer is worthless and probably weakens the adhesion. If there's no "tooth" to grab, it just won't work. On a proper surface, the stuff is most certainly permanent. I painted the transmission case on my race car with the stuff--just painted it over the raw aluminum casting, and it looks like new. Fortunately, it's under the car where the UV rays don't get to it--POR-15 does discolor in the sun, which is why they offer a topcoat.

 

Almost every failure I've heard related to POR-15 is from a guy who had fresh clean metal or tried to apply it over some other coating, and it peeled off. Yep. They even tell you that'll happen right in the directions. There needs to be an 80-grit scratch on the surface (or worse) for it to work. 

 

If you have clean metal, I'd recommend powdercoating or a proper urethane paint. I've had good luck with Rustoleum on tools and things I've made in the shop, but I don't know if I would trust it for a frame. That's a judgement call for someone with more experience with it. 

 

I have no affiliation with POR-15, but I've used it and like many other things automotive, misuse gives you poor results and then the myth propagates. It's good stuff, but you need to use it on the right application under the right circumstances.

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When I restored my 48 Ford Conv. I sandblasted frame and used POR-15.  Today I can take a hamper and hit it hard and will not chip off.  I bought an enclosed trailer from the South. Was shipped to Maine and rusted on way. I wire brushed the bad rust and used POR-15,  Messy to work with but won't have to think about rust again. Bad part is no reducer with take it off your skin. have to wear it off. Wonderful paint. You do have to top coat if out in sun. Good Luck

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One disadvantage with   POR 15  ( and probably also  KBS....I'm pretty sure that both are isocyanate type coatings )

is poor shelf life after the can is opened.  

 

When I use it I...………

 

        Dip out of the can with a new plastic spoon or ladle  whatever I need for the task at hand

        Promptly put some Saran wrap over the can opening...….I don't leave the can open any longer than I have to.

        Then put the lid back on 

        And I store it in a refrigerator ( non-food storage ) after the can has been opened

 

And even so it has poor shelf life after the can has been opened,

This is because moisture catalyzes the curing of isocyanate type coatings.....and it doesn't take moisture to cause this

 

But is promptly applied it is PERMANENT.

 

Jack Worstell

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I have been using POR15 and POR15 TopCoat for several years, and love all of their products.

 

NEVER open the lid!!!!  ANY paint on rim/lid WILL prevent opening again!

 

Poke 2 holes in the lid... one for vent -  one for pouring, and screw-in 2 ea. 3/8" lag screws.... this limits "new" air in the can...... currently my can is about 3 years old...not refrigerated and seems to be still useful...

 

I store the POR15 can upside down so if a skin forms it will be at the bottom of the can.

 

I used these 2 coatings on my 1909 Sears Motor Buggy step plates and pedals.... after 8 years,  no wear and still have like-new surfaces.

 

Sandy Rose

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Sandy.….thanks for the tips...….sounds promising,    I'll give these ideas a try.

 

A product  I like is "Mastercoat"....which is also a moisture cured isocyanate type coating.   (and It has the disadvantages of an

isocyanate  based coating.)

It has a dull aluminum sort of appearance   and it is "toothy" which means you can

apply a top coat with no need for surface prep     e.g.   no scuffing with sandpaper.

 

Jack Worstell

 

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When I was in the Navy and our aircraft carrier was in dry-dock,  I asked the guys painting the hull what they used to combat/prevent rust.  They told me they used Ospho to treat the metal first then painted it.  The phosphoric acid in it changes the rust (iron oxide) to iron phosphate and paint sticks to it very well.  So in 1979 I was painting my 39 Chevy which had some large paint/ rust blisters about the size of saucers on the roof and trunk.  I wire brushed the rust and painted it with ospho.  The next day I did that all over again.  It turned the rust a black color with some white powdery residue.  I brushed the powder off, lightly sanded the area and primed and painted it.  To this day not one of those blistered areas as bubbled or cracked.  I swear by Ospho.

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On 10/13/2019 at 6:47 AM, Mark Kikta said:

it changes the rust (iron oxide) to iron phosphate and paint sticks to it very well

I too use Ospho as soon as bare metal is exposed by sand blasting etc.  It prevents flash rust for up to a year in my wet NW climate.  And, unlike Por 15, it is relatively  inexpensive and available in most hardware stores.

 

http://ospho.com/

 

Edited by Mark Shaw (see edit history)
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On 10/17/2019 at 7:40 PM, B Jake Moran said:

 

KBS is better than Por 15.  But - why not just powdercoat it?

 

Most people don’t have the equipment nor large enough oven to do Powder Coating at home, but someone can use a DIY approach with a quality product and it’s more affordable and easier.

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  • 4 weeks later...

I have lived on boats most of my life. One of the yachts I owned was a 1956 FeadShip made of steel in Holland. The fight against rust was EPIC. Warm salt water is about the most corrosive environment in the world! 
 I have been a fan of OSPHO but find that since it’s a “Marine” product, it’s two to three times as expensive as normal hardware products. Metal Prep from Home Depot has the same phosphoric acid content but is half the price. 
I yearly had to grind area on the hull to bare steel, applied phosphoric acid and let dry. I wire brush the white powder then apply coal tar epoxy for large areas and POR 15 for smaller spots.  
 Whether using above or below , any top coat needs to be applied just after its past tacky or you will have a heck of a job sanding it to top coat it. POR 15 doesn’t have any UV filters and must be top coated if in the sun for prolonged periods of time.

 I have used both POR 15 and Rustoleum each on the frame of one of my Cadillacs. When using Rustoleum, I usually chill the can in the refrigerator over night so when using it, the paint has time to flow out before hardening. 
 So, that’s my 2 cents!

Edited by yachtflame (see edit history)
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