To anyone who has used POR 15 in the past did you strip your bay to bare metal or did you apply it over what was there?

Here is my case... Currently my engine bay is painted with rustolium. I am in the process of a wire tuck and cleaning up a few odds and ends. I would like to take the time to fill in unused holes and smooth out a few areas. So some parts of the bay will be down to bare metal.

I am just curious how far I have to go to get a good finish with this stuff. Also did you use the POR20 that they recommend laying down first?

Thank guys!

You can do both but I believe it adheres better to bare metal. When I did the bumper on my Jeep it came bare so all I did was use the metal ready which is just phosphoric acid. That cleans up the rust and etches the steel for the Por15 to bond to. Been 4 years with the stuff already in daily driving thru all seasons and 50K miles. Other than a couple of spots where the rust got through to the thin coats on corners, the rest of it has held very well. My only complaint is it doesn't seen to do well in direct sunlight. I had gloss black and it has turned into a sooty flat black. Shouldn't be a problem in the engine bay.

I always clean the area and get rid of all the dirt and rust I can before applying por15!

Thanks Tim. I am sure under the hood it will be fine but thanks for the info.

Dsmkauai, do you apply it over existing paint? Just clean the surface?

I am thinking if I wire wheel the surface rust, clean the dirt and then take some sand paper and knock the rest down a little then apply the POR15.

I coated the floorpans front to back in POR15. I degreased it, then painted it. If I were to do the engine bay I would do the same. Its been 4-5 years and it is still holding up well. I load tools/tires/jack/fuel in it to go racing, so it is metal to metal stuffing.

Awesome! Thanks you!

A good friend just did his engine bay in POR-15 and was having problems with it but finally, after several attempts, got it to adhere correctly.

I'll let him come in here and give you the details but it does matter what you clean off the existing surface with before painting it or you'll have adhesion problems or the paint will fish eye.

We clean the surface up till bare metal getting as much old paint as possible off and other gunk and rust. I usually just use some acetone for final clean and then por-15 prep and ready to etch the surface before I por-15 hasn't given me problems yet. And trust me bro we use a lot of this stuff out here in Kauai. At my shop "Off road fabrications" I do a lot of rust prevention and restorations! We pretty much por-15 everything we can ! Stuff works!!

Use isopropyl or denatured alcohol NOT acetone.

I just finished painting my engine bay 3 times with POR-15 silver. The first two times the paint reacted with the solvent I used to prep the surface before the paint.

First time I used denatured alcohol and the second time I used lacquer thinner.

On POR website it says not to use any solvent based cleaners in BOLD. Would have been nice if they put that on the can! After research I used a Scotch bright pad and AJAX to clean, Then used the water based cleaner called (degreaser) sold by POR 15 for prep. then washed with soap and water and then blew dry with a heat gun.

Third time it went on good, I used a nice paint brush to apply two coats. The second time I used a new HVLP detailing gun and tried spraying but it puts down a lot of paint and is hard to control. If you spray, use the POR brand solvent with the paint diluted to the max recommendation of 5%. The POR needs to be put on in multiple thin coats. It takes about 5 hours for each coat to become tacky enough to re apply. I felt like I had more control with brushing so I did that the third time.

You can lightly see the brush direction on the paint but its kinda cool looking. It sets up like a rock, Super smooth and hard like glass. Its also very shiny like its clear coated. I also have the POR-15 clear coat that I am about to spray on tomorrow. My friend used black with the POR clear coat spray can and you cant see the brush strokes. Its super nice, shiny and smooth.

I prepped by sanding most of the way threw everything with 220 then 320.

The POR 15 is water sensitive so it hardens faster the more humid it is. If its too humid the paint will develop bubbles from the rapid curing.

Blaze that was great info!! Thank you!!

Any chance I have any pics?

Thanks guys!

If you brush, You want to put down very thin coats. It runs very easy so don't go on too thick. Multiple coats is the key.

I forgot after I sanded everything. I used POR primer in a spray can.It only took one can of primer and one pint of POR silver.

I sanded down the primer with 320 to rough it up to help the POR grab. The first two times I was able to blow off the POR in strips with 150PSI of air. It didn't adhere very well.

I included: (Not in this order)
Pic of bay primered.
Pic of Finished POR bay.
Pic of finished fender well.
Pic of chemical interaction to the paint the second time.

here is a better shot of the shock tower

They say on the website it wont hold up in direct sunlight but besides that its great. i think they make a clear or topcoat if you wanna put it in the sun. i use there cleaner first then a scotch brite then cleaner again. On rusty spots i just wire wheel, clean and put it on. There website has some good info on how to use it. I just painted mine with nasan. And it looked great until i spilled brake fluid all over the strut tower.

Personally, I would go with Rust Bullet over POR-15. Rust Bullet actually reacts with any existing rust, chemically altering it into part of the coating. When I got done with my car, the rust Bullet coating was hard and durable. I doubt I'll ever deal with rust in that area of the vehicle ever again. I decided to go with Rust Bullet after seeing good results on some other vehicles, and reading up on some of the testing they performed Rust Inhibitor Paint | Stop Rust | Rust Corrosion Inhibitor | Rust Converter.

Another perk to using Rust Bullet is they have a lot of other products that work well with each other. They have stuff to prep the surface before application and also offer a top coat called BlackShell that can be used for finishing BlackShell - Rust Bullet LLC.

POR-15 is very similar to Rust Bullet, and is designed to bond to rust. It focuses more on sealing it from oxygen and moisture by creating a non-porous hard coating, though. Again, a very permanent coating, that would probably prevent rust for the life of the car if applied properly. I believe this is probably a very good product as well, but they just didn't have the same amount of testing and info Rust Bullet did. Regardless of the product used, you need to properly prep the surface to get a good bond. That means removal of any rust, and a clean dry surface before application.

I had a few small rust spots on my Galant VR-4 I needed to deal with. I removed all the rust and preped the surface with Metal Blast, a product from Rust Bullet Metal Blast - Rust Bullet LLC . I applied the Rust Bullet (grey in the pictures below) rust inhibitor over the entire front clip and then got some factory matched white (WO9) from automotivetouchup.com and I applied directly on top of the Rust Bullet. I used the BlackShell to do the wheel wells. Overall, the project turned out great. I used a HVLP gun to do everything, but Rust Bullet can also be painted on with a brush if you want. Here are some pics of the entire process.

Everything I used:



After the W09 base and clear:




The core support was one of the few areas I spent time sanding and smoothing before shooting the base and clear coats. In comparison to the other areas I just shot without much sanding, it looks glassy smooth.





Lastly, I thought I'd put a few shots of the overall progression.

Driver side rust area:





Lower front window support.



Front view of the clip:

Driver side of the clip:





Driver fender well:

Very nice work bro! Came out really good!

Thanks! I ended up pulling the motor and doing the same thing to the engine bay as well. Here are a few more before and after pics...

Engine Bay:







Front Sub-frame:





Brake booster/Strut tower:





Firewall:




Battery location/passenger frame rail:

Wow! Thank you for taking the time to post all that up! That definetly gives me sr other good for thought!

While the forum was down it have me some time to look into rust bullet. I think I will be going with them over POR. The amount of information on the site along with the testing and results against ASTM standards really impressed me. It will be about a month before I get it done since I am moving from Ma to Ohio at the end of the month.

Thanks for the help everyone.

I use the Rust Bullet Metal Blast conditioner before I paint/powdercoat parts on my cars. It's a phosphoric acid based cleaner that etches the metal, and helps kill any surface rust.