Longevity of POR-15 on undercarriage?

[TexAndy]

Those of you who have used POR-15 as an undercarriage coating/rust preventative on your cucv, how well has it lasted over the course of a few years?

I'm considering using POR-15 to undercoat my M1009. Primarily for rust prevention rather than noise abatement.

One thing that concerns me a bit is how hard POR-15 is when it is cured. Will the sheet metal expand and contract with temperature change and cause it to separate from the POR-15? Or is there not enough movement to cause a problem?

 

[acesneights1]

It sucks. Use rustoleum v4700 series industrial paint. It is only available through places like Grainger. We use it on the Fire Hydrants at work and it has taken a brutal beating up on the state roads.
I put 5 coats of Por15 on my frame after sandblasting a few years ago and it peeled off in sheets when I powerwashed the frame.

 

[Bob H]

POR15 will only stick to steel, once cured on the steel it will last forever!
It will peel off of anything else. Paint won't even stick to it after it has cured.
I did a spot on a quarter panel years ago, several years later the panel rusted out around the POR15, I had kept that piece for quite awhile but

 

[swbradley1]

That's good to know as I was going to buy some to put on spots on my pickup.


EDIT: I was commenting on the good to know that it was crap paint.

I do like Rustoleum though.

 

[pigpen60]

Do you mean v7400? Searched v4700 on the rustoleum site and came up with nothing.

 

[Drock]

Agree don't waste your money on POR15. The idea of this stuff is to paint over rust. So you don't have to take the time to clean off all the rust. In other words let your money work for you. The problem is as stated earlier is it WILL NOT stick to anything painted. And buy the time you buy all the chemicals necessary to make it work (around $300.00), And clean off any paint in the way. You could have just cleaned off all the rust and painted it with anything else. I prefer rustoleum 7777

 

[MidnightDuramax]

I second acesneights1. Por15 is a waste in my opinion. used it on two trucks and in less than a year half to 3/4 fell off. I prepped everything the way Por15 instructed to the "T". I then stripped it all down and sprayed Rustoleum on with an HVLP gun and 3-5 years latter still looks as the day I put it on. I will never use Por15 again. I use Rustoleum for all my frames and below body line items.

 

[Keith_J]

Interesting. I used it on my MEP002A generator in 2011 and it is still tightly bonded. The generator case was rolled from hot rolled steel, the mill scale wasn't removed so that was coming off in sheets, after all that was chipped off, a single coat of POR was rolled on.

Coating any used undercarriage is an exercise in futility as road dirt is next to impossible to remove. Best bet is to coat it in used motor oil...leakers don't rust

 

[cucvrus]

It is worth the effort to clean the rusty surface as good as humanly possible. Pressure wash first. Let dry and re clean again. Then you can use Rustoleum Rust reformer. After you clean it real good use an acid surface prep and spray the rust reformer on the area. If you want to top coat it wait 24 hours and apply a good undercoating / rustproofing something that dries. Not the type that stays waxy that stuff eventually just wears off. But if you spray over dusty flaky rust areas. Nothing is going to work. You need to use a good wax and grease remover. I even spray it out of a siphon gun and then wipe and brush the area until it is clean and dust and grease free. No finish will stick to the surface if dirt / grease and dust are present. The prep work on refinishing is 99.9% of the work to the finished product. It is worth the time to achieve excellent results.

 

[milradioman]

I used POR15 on a vehicle 20 years ago, it is still sticking and holding out the rust, at the time I attempted to apply multiple layers per the instructions, because "more is better", apparently I did not do it exactly right and the top layers peeled off later, but the first base layer was ok. I use Rustoleum flat black 777 on all my undercoat jobs, I have applied it on metal exposed to the weather and it last forever, it is the best easily obtainable paint I know of. On my recent project I cleaned the rust off of the floor pan, applied Rustoleum, then paint on bed liner just to make sure it never wears though.

 

[tennmogger]

It's great! I take the other side of the argument. I started using POR15 for rusted metal in the late 90's and most applications have not deteriorated at all in over 15 years. POR 15 has been used here to plug a bad gasoline tank on a 'mog 404, perforated in over 50 places by some kind of splattered acid, and the POR 15 sealed it completely. The floorboard on one 404 was pitted with rust, cleaned, and coated with POR 15. Even heel abrasion has not taken off the POR 15 coat.

IMHO, anytime POR15 peels off there was a preparation problem. Proper prep is part of the cost of a paint job with any paint. Multiple coats of POR15 are almost a guaranteed problem unless you spray the second coat while the first coat is still in the tack stage. The POR15 instructions are clear on that. Coats made at a later time are almost guarantee failure. One heavier coat is the way to go.

A top coat in desired color should also be applied in the tack stage of the POR15, otherwise you have to wait for complete cure of the POR15, abrade the surface well (!) and then paint. Otherwise the top coat will peel. That application should be done on smaller areas so you can catch the POR15 at the right stage. Or, use the topcoats provided by POR15 company which somehow chemically link to the POR15. I just spray the top coat of whatever top coat I want during tack stage. I just did that on a 404 Unimog restoration and top coated with either Rapco 383 or Rustoleum flat black.

BTW, I like Rustoleum too, but use it in less critical applications.

Bob

 

[swbradley1]

POR15 is not for open sunlight. I do know that much about it.


https://www.youtube.com/watch?v=OMxCWNUHNoU

 

[brasco]

I'll put my in here too. First of all, I have never used POR-15 but I have "tested" Rustoleum in extreme conditions. In the early 1990's, I worked for a company that built a carbon steel rack to hold paint test samples in an industrial humidity test chamber. The rack was painted with Rustoleum and placed in the test chamber to hold the actual test samples. That rack stayed in the test chamber for years and years without any major rust. The conditions in the test chamber were 95% Humidity and 95 Degrees at all times. When I left the company a decade later, that rack showed only a few small sections of rust after all that time in extreme humidity. Bare carbon steel test panels would start to rust after a day and were totally covered with rust in a few weeks. I was really impressed by the performance of Rustoleum paint and have been using it ever since.