POR15 and other cancer preventiveness

I have used POR15 in the past and liked it except its cost, smooth bedliner has worked "okay" at this function at best, general paint seems just to buy some time...

I have removed my underbody HDPE protection from the rally car to find well, not a a pretty sight... 2 years of not removing this and doing some ice racing/winter rally/misc gravel/rallyX etc seems to have dropped a lot of dirt underneath as well as moisture. 

I spent about a day underneath and got the worse of the two sides done by grinding and wire wheeling everything down and put a whole can of primer on it to seal it. Now the question is can I POR15 over the top of the primer for a belts and suspenders approach? As I'm sure i didn't get every last cubic mm of rust. Or does this defeat the purpose of POR and it doesn't work?

whats the hive mind? southerners need not apply as they have never seen rust before. 

I'm pretty sure POR is supposed to go directly on the rust with nothing in between.

Yeah, from what I've read, the POR15 goes on the rusty metal.  Even putting it on clean steel can give bad adhesion versus rusty steel.  Over paint is a no-no.  They Say.

In reply to fidelity101 :

Not sure about POR15 but RustBullet (one if it's major competitors) is basically just clean, degrease, remove flaky loose rust and paint over what remains.

Tom_Spangler said:

I'm pretty sure POR is supposed to go directly on the rust with nothing in between.

problem is there is plenty of dirt and such that cleaning it would get to the rust would take some of the rust off as is. 

How large of a compressor do you have? I was unimpressed but rustbullet when using it but have loved soda blasting then hitting clean metal with Rust-Oleum rust converter as a primer, to be followed by a high build primer for blocking before top coat.

I can confirm from personal experience that POR-15 will not adhere to clean metal or paint.

I've had great results with Rustbullet covered with some Rustoloeum 

My procedure for the rally car's wheel wells and undercarriage is just to use the biggest thin gauge wire wheel I can get, "clean" the whole thing (rust, dirt, flaking paint, whatever comes off) then repaint with Rustoleum enamel once per season.  Seems to work OK and is relatively quick to do.

fanfoy said:

I can confirm from personal experience that POR-15 will not adhere to clean metal or paint.

I've had great results with Rustbullet covered with some Rustoloeum 

I may do an A to B comparison. Driver side do the wire wheel prep then primer and use my existing tractor paint I have laying around and on the passenger side straight up POR15. in 2 years I will have to re-do my seat belts when they expire so I will see how each side ended up.  To do this I need to remove my underbody guards and expose the floorboards. 

I need to do a touch up on the suburban on the frame rails and this stuff comes in handy so much that I think I'm gonna buy a gallon and use it where I can. 

Do not apply to hootus. 

In reply to Appleseed :

is hootus my wang-dang?

Yes. 

I think POR actually recommends wire brushing to get any loose flaking rust off then spraying    With their converter which converts ferrous oxide to a phosphate. The converter is really just phosphoric acid which you can get at Lowe’s or Home Depot under various brand names. The rust color turns to a gray/black color. They recommend this step on bare metal also. I did a rear end housing using this method and have had not adhesion problems with the POR 15 or the topcoat of paint. You can use a pump spray bottle for the phosphoric acid but you need the wear a mask and eye protection. All the safety rules about the hootus apply and also be prepared to wear POR 15 on your skin if you don’t wear gloves.

I haven't tried hitting rust with a converter first and then following it up with POR-15, but can say that if you don't, POR doesn't go that deep into the pores. It's still a tough finish, but when a bit of it scrapes off, I still find rust under.

The POR 15 is pretty thick so probably doesn’t penetrate well. The phosphoric acid actually stops the rust if enough is applied to soak all the way through to good metal. The POR 15 is really tough stuff but like powder coat if scratched or breached the rust can run on the inside under the coating until chunks fall off without you even knowing there was a problem.

Some else mentioned it, but POR-15 sells a metal prep for smooth/clean surfaces. I wheeled, welded and generally prettier up the steel tub in my FJ40, hit it with the metal prep, let it dry overnight, and then did 2x thin roll on coats of POR15 the next morning. 3 years later it has survived everything, including a leaking rear heater that put 2 quarts of radiator fluid inside the cab with no issues. One thing with POR15 is the need to topcoat, and any UV exposure with compromise it (according to The Prophecy, at least). 

I was impressed, but I have nothing else to compare it to, so take it for what worth.

I’m a believer in POR 15. It’s tough against impacts of rocks and wears very well. My only complaints is it is somewhat expensive and once a can is opened if not fully consumed it hardens in the can. I have tried cleaning the cap real well, storing it upside down, putting in plastic bags and even putting in the shop refrigerator.  Still hardens. Now I buy smaller cans instead of one big can so that I use the whole can and do not have to store opened cans. Anyone else have this problem or a solution?

My usual go-to for protecting metal lately has been: clean it up, apply POR15 metal prep, then POR15.  Let it dry, apply a coat or 2 of Rustoleum semi-flat black for UV protection.  Once that's dry, apply a heavy coat of CRC SP400 (heavy, waxy rust preventer).  The SP400 slowly wears off over time (so eventually you'll need to clean the dirt off and reapply), but it's an extra layer of protection and helps keep stuff from wearing / chipping through the paint or POR15. 

In reply to pirate :

The trick is to never open the can. Drill the lid instead and pour what you need in a can. When you're done, use aluminum tape on the hole. To use again just remove the tape or drill another hole. It will still harden, but slower. At some point a crust will form on top of the remaining paint in the can. Either drill it or flip the can and start over.

Although I'm a southerner, I live at the beach where even plastic rusts.

I did the trunk of my old Comet with POR15. Following the directions on the can I wire brushed off the big chunks, sanded any shiny spots the original paint somehow clung to, and slathered on that black gold. Adherence was good and I saw no more trunk rust for the next 2 years I owned that POS.

Rocambolesque said:

In reply to pirate :

The trick is to never open the can. Drill the lid instead and pour what you need in a can. When you're done, use aluminum tape on the hole. To use again just remove the tape or drill another hole. It will still harden, but slower. At some point a crust will form on top of the remaining paint in the can. Either drill it or flip the can and start over

Interesting I have never heard that before but will try it!

albenpure said:

{canoe} cancer treatment
 

Very interesting article, but you are a canoe.  

Tom_Spangler said:

I'm pretty sure POR is supposed to go directly on the rust with nothing in between.

I have peeled POR15 off like the joke about buying used paint ("it was shaped like a house") after this method.

Yeah, POR15 is a poor material; its a phosphor, the same stuff in coke, and causes a chemical reaction on the surface with rust to leave a metal oxide called Magnetite. It's not very strong on the surface, and it's brittleness means it chips off in my experience.

There's a guy on youtube I watch I can link to later, who makes an underbody spray out of melted wax rings for toilets, used motor oil, and a solvent (I think he either used diesel or kerosene). As it dries it leaves a film layer that prevents oxygen from getting to the metal, and he's got tons of videos showing that it works.

In reply to GIRTHQUAKE :

Kinda crappy wax used....

(I'm here daily....)