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Username Post: POR 15 questions and pics inside.        (Topic#344525)
Posts: 279

Loc: northern California
Reg: 01-27-17
05-05-17 05:16 PM - Post#2689746    

I kinda like my truck having rust in certain spots, but I don't want the rust to spread anymore or else it won't look good and will eat up through the metal.

Here's some examples of some heavy rust spots on my truck that I want to keep at bay and from spreading any further.

Now, I read that you apply marine clean first, then metal prep and then the POR 15, is that correct?

Do you think that based on those pics of my truck, that POR 15 will keep the rust from spreading any further?

Another question, can I use POR 15 without sanding anything down? I just want to stop the corrosion/rust from spreading any further. That's all.

And what color is POR 15? My truck is red, so is POR 15 a clear substance that won't make it look odd?


Very Senior Member
Posts: 4070

Reg: 12-29-02
05-05-17 07:57 PM - Post#2689768    
    In response to Eric_Gary132

I've tried POR15 a couple of times following their instructions exactly and didn't have any positive results. The rust just kept spreading until the POR15 peeled off in sheet. I then tried wire wheeling the surface first to take off most of the rust and it worked no better.

Since then, I have come to the conclusion that simply getting the rust off is the best solution. Sandblasting and painting with a proper primer for bare metal works well. Grinding/sanding/wire wheeling most of the rust off and then using a product like Ospho with steel wool or a wire brush to work the surface until it's clean before using a proper primer works too. Electrolosis on smaller parts works and then painting with a proper primer for bare metal works too.

"7th Year" Silver Supporting Member
Posts: 4017
Loc: Salt Lake City
Reg: 06-20-09
05-15-17 06:20 AM - Post#2691389    
    In response to 65_Impala

You can buy it in at least two colors that I know of: black and silver.

Edit. Just checked their web page and I see gray and clear also available.


'95 K1500 Z71 EC Short Step 5.7L+0.040/NV3500
'00 Explorer XLT 4.0 V6 Auto
'94 K2500 5.7 NV4500 ECLB - SOLD
‘87 GMC S15 SCLB 4.3 Auto - SOLD

"The only thing necessary for evil to triumph is for good men to do nothing" Sir Edmund Burke

Forum Newbie
Posts: 75
Loc: Enterprise, MS
Reg: 01-12-17
05-26-17 09:06 AM - Post#2693018    
    In response to CowboyTrukr

The best way to deal with what rust you have is to sandblast it or take a wire wheel on a side grinder and grind it off. Spray it with some Phosphoric Acid, let it sit for 5 minutes or so an rinse, wire brush and repeat. Do this until you no longer see the phosphoric acid turn any rust black. At this point spray it with a self etching primer, then a sandable primer filler, sand and repeat and then a primer sealer. Repaint it and be done with it. I only use POR on the underside of the truck because it is not UV safe and will break down if left exposed to sunlight. Por will slow the rust down until you can fix it.

Silver Supporting Member
Posts: 113
Age: 67
Loc: Florida and UK
Reg: 05-02-17
11-26-17 12:03 PM - Post#2715799    
    In response to 65_Impala

POR 15 sticks like nothing I've ever seen. Once you put the lid back on the tin you'll never get it off again. I had to drill a hole in the lid to get back into it. That's why they sell it in small tins so you don't waste so much.
I actually use it as a sealant also - I fitted new freeze plugs in an XK engine I'm rebuilding & painted the edges with POR before I fitted them. I hope I don't have the job of getting them out again!

Posts: 28737
Age: 48
Loc: Texas
Reg: 08-01-03
11-27-17 05:16 AM - Post#2715886    
    In response to Hugomiller

That's why they suggest (or used to?) using a layer of plastic wrap across the can before re-applying the lid. Worked great for me.


06 Silverado ISS / 06 Silverado SS / 06 300C SRT8

"3rd Year" Silver Supporting Member
Posts: 481
Loc: Western NY
Reg: 06-15-02
01-14-18 11:15 AM - Post#2721018    
    In response to someotherguy

Some observations regarding POR15:

POR15 sells many different items but it hasn't always been clear to me which are, and to what extent, they prevent or seal a surface to stop rust from coming back. My perception was always that their black was their original product for that purpose and anything else may not perform the same. POR does not convert rust it instead prevents anything from permeating through to the rust so the rust doesn't continue to grow (my understanding).

The POR15 rust preventative coatings are not UV resistant. If you plan to use POR15 and you don't want it to dull you need to top coat it. I have top coated with other paints and it does work but if you do it too soon the top coat gets absorbed into the POR and if you wait too long adhesion is not the best.

POR takes a very long time to dry but because it does it wets-out very nicely. I've noticed, and it seems it should be expected, that if you coat over something heavily rusted to the point the rust is basically delaminating the material you have little chance of the POR doing much other than coming off with the outer rust layer.

If you spill POR on yourself wipe it off fast because it sticks to skin better than almost anything else. Acetone will take it off but even Acetone doesn't do much if it is allowed to fully dry. If you have a plastic coffee or lemonade mix scoop you can use it to ladle POR into a plastic container. After use just let the plastic ladle and container fully dry. POR will NOT stick well to plastic and comes off in sheets or even as an exact form of the plastic scoop once it is fully dry.

I found myself contacting POR customer support with questions on information they provided which was just vague. They may have improved but things like which coatings are rust preventative and is there any difference between colors or products as far as future rust prevention. My perception was yes there is and black was my go to color.

Despite what have been pretty good results with POR15 I've since tried Rust Bullet Products. Rust Bullet seems to offer some test report type information. When I dug into it there is some good information as well as so many listings it also makes it difficult to find which is and which is not useful information. They did have one report where a bridge authority performed some testing with their product in both the Silver and Black colors versus their traditional best practice solution. I am giving the account by memory of reading this about 2 years ago but I liked how they showed in the report that there was even some difference between the silver and black Rust Bullet products (they didn't seem to be hiding this and silver was better than black). I also liked that Rust Bullet is UV resistant. Based on what I've seen as far as information offered more than stating I have long term experience with both (I don't) I have moved to Rust Bullet. There are other POR15 products which I like such as their POR Putty. Their engine paints also seem to coat very well although I was never certain how well they held-up to heat and so at times I was a little reluctant to use them on some parts of the motor.

Silver Supporting Member
Posts: 113
Age: 67
Loc: Florida and UK
Reg: 05-02-17
02-18-18 10:59 AM - Post#2724760    
    In response to toro455

The POR15 system consists of a cleaner (was called Marine Clean, now cleaner & degreaser I think), followed by 'Metal-prep', which is a species of phosphoric acid, and which (I believe - but I am not a chemist) converts iron oxide to inert iron phosphate. The you cover it with two coats of their black paint, which is intended to prevent air & water getting at it & thereby stopping it from rusting any further. I like it. That paint certainly sticks better than anything I've ever come across! And it goes on very nicely indeed.


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