POR15/Rust Bullet advice to coat underside?

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POR15/Rust Bullet advice to coat underside?

Postby toayoztan » Tue Mar 02, 2010 10:49 pm

I was curious what you guys recommend on coating the underside/fender wells of the car?

I want to do this myself before sending the car in for a paint job.

Should i scrub and clean it before applying it?

How can I check for any hidden rust...should I try to peel back any of the stock coating underneath?

I just want to clean things up underneath and seal it, so any recommendations (if any other than POR15 and Rust Bullet) would be helpful, thanks!

Bryan
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Re: POR15/Rust Bullet advice to coat underside?

Postby Sifu » Tue Mar 02, 2010 11:12 pm

If you're going to apply POR15 make sure you clean off as much junk as you can (old paint, dirt, oil, rust, etc.). Their marine clean is suggested but I've just used an oil/wax remover and it's holding well. I didn't spray mine because you can't dilute it too much (plus I don't own a gun nor would I try it with this stuff, hardens pretty quick) but I prefer using a foam brush.

Don't apply straight from the container. A little goes a long way. 2 coats and you should be good. I have gotten away with one coat on some surfaces.

Sorry if this is a bit fragmented... I just woke up from my nap... :oops:
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Re: POR15/Rust Bullet advice to coat underside?

Postby toayoztan » Tue Mar 02, 2010 11:32 pm

Hah, seems like we could all use naps with the pain the alltracs give us.

So how much do you recommend I get, gallon? I'll probably use a brush or foam to apply it.

I'll make sure that the underside is clean (i'm taking pretty much everything off, suspension, subframes, etc.). I guess i'm more curious about taking off the stock coating (there is a stock "rubberized?" coating from the factory, right?). Do i just wheel brush it off?

Would you guys recommend doing all of this before a paint job? If i decded to do it aftewards, I cold use painter's tape and plastic sheeting to cover the new paint job.

I want to get my car into the shop within 2 weeks, but I'm not sure if that's going to happen...depends on the shape of the underbody. I'm scared to see how it'll look lol.

All the other parts, like suspension and subframe components, i'll be powder coating myself.

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Re: POR15/Rust Bullet advice to coat underside?

Postby Corey » Tue Mar 02, 2010 11:44 pm

My friend POR-15'd the entire underside of his FD and the subframes.

First he had the subframes sandblasted.

He opted to spray the POR15 on, and it looked great.

The parts he didn't spray in POR15, he coated in rubber rock guard.
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Re: POR15/Rust Bullet advice to coat underside?

Postby Sifu » Wed Mar 03, 2010 1:11 am

First thing first. Triple check that everything on the underside does not need any major body work. That needs to come first.

One gallon should be enough. I purchased a small can to test out but it goes a long way if you apply it well. If you can sandblast it would be great, if not just make sure you apply it to every nook and cranny.

I first applied it with a brush. You can see some of the strokes still and some of the bristles fell into it. Foam brush works way better because it lays more evenly and unlike a brush the POR15 (it's pretty thick) will not be trapped. The brushes are pretty much garbage after the first use and foam brushes are much cheaper.

The undercoating I would try to loosen as much as I can. It's best to get rid of it all but that can be near impossible if you don't have a chassis rotisserie. My MR2 had some shotty undercoating on it (that crappy 3M spray on junk in a can). I scrapped off as much as I could, sprayed an oil/wax cleaner, scrapped some more, sprayed oil/wax cleaner, dry and applied POR15. One coat looks like it'll get you through it, but two coats never hurts. You'll probably have to wait a few hours to dry (esp. in the winter cold) or half a day.

You can sand POR15 and paint right over it. I can't remember if you need a primer but I'm not worried since I will save money by not painting the underside.
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Re: POR15/Rust Bullet advice to coat underside?

Postby MWP » Wed Mar 03, 2010 1:55 am

If youve got small areas of rust to fix, then sure, use the Marine Clean, Metal Ready & then POR15.
There is no point in doing the whole underbody with POR15 over the top of the existing paint/primer though.

POR15 also isnt quite as strong as the company claims.
Itll chip & flake away from rock/debris hits under the car.
It also wont stay nice & shiny like it looks shortly after painting... itll dull over time.

So my advice....
Fix rust areas with POR15.
Coat whole underbody with a thick bituminous/tar underbody sealer.

The tar sealer is cheap, you dont need to clean as much before applying, and will last a lot longer than just POR15 in that harsh environment.
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Re: POR15/Rust Bullet advice to coat underside?

Postby toayoztan » Wed Mar 03, 2010 2:48 am

Sifu, they stated you don't need to paint the POR-15 if it isn't exposed to UV rays, which I doubt the underside will see any sun unless you rally and flip!

MWP - got any recommendation for which tar sealer to use? I'll have to look into that too.

I was thinking a rubberized coating would work, applied over POR15 rust areas, and that should suffice...

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Re: POR15/Rust Bullet advice to coat underside?

Postby Sifu » Wed Mar 03, 2010 3:10 am

No you don't need to paint it if you don't want to; some people like to though because you can use it for small body work (I'm testing the results on my MR2 as well). I also purchased the matte version and not the shiny one.

MWP I'm not sure how rust is in your location but here in the US Midwest our roads are completely smothered with salt (thank goodness I don't drive the projects in winter, but they do sit outside during the winters). I'm probably going to cover the MR2 underbody since it's really not that much. I don't care much for resale value or selling a 'classic' because I plan on using and keeping them. I just want to make sure rust never returns...
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Re: POR15/Rust Bullet advice to coat underside?

Postby MWP » Wed Mar 03, 2010 5:15 am

A thick coat of a sealer (tar/bitumen/rubber) will protect better than POR15 against salt too.
Ive used POR15 quite a lot, and in a few places (like seams), bolt holes, etc, it has cracked... hence why i suggest using a sealer coat over the top for extra protection.

Here is a photo of under my project car ('77 Celica).
Its brush painted (f*ing hard work to do) with thick tar + sand mixed in.
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Re: POR15/Rust Bullet advice to coat underside?

Postby Sifu » Wed Mar 03, 2010 12:27 pm

I was given this recipe for an oil/tar recipe. What do you think?

NEVER add 3m rubberized coating to anything on the car. The rust will come back ten fold. Do not just spray rustoleum on the underside of the car. The only way to slow the rust is to use oil/grease with phosphorus acid and zink.

You can mix a cocktail of oil using;

Mostly Bar&Chain oil - contains Ph
Small amount of MMO - solvent
ZDDP - zink
small amount of Machine oil.

Use the Oil to coat the seams and rockers or any where salt spash can access, You can use a Marine grease to coat the under panels to make a barrier between the metal and salt.

Ive used Rust bullet, and the rest came right back. I used the Bar&Chain oil, and in those spots there is no sight of any corrosion. Think Waxoyl
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Re: POR15/Rust Bullet advice to coat underside?

Postby turbo4wd » Wed Mar 03, 2010 4:55 pm

If you've already got rust, maybe consider using a rust converter?

http://www.eastwood.com/rust-solutions.html
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Re: POR15/Rust Bullet advice to coat underside?

Postby 88gt4DE » Wed Mar 03, 2010 5:37 pm

Im testing out the stuff we are coating tacoma frames with right now under a recall ... just did the fuel tank thats to go in tomorrow and eventually the rest of undeside of car and shock towers ...
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Re: POR15/Rust Bullet advice to coat underside?

Postby MWP » Fri Mar 05, 2010 10:58 pm

turbo4wd wrote:If you've already got rust, maybe consider using a rust converter?http://www.eastwood.com/rust-solutions.html


POR15 Metal Ready is rust converter.
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Re: POR15/Rust Bullet advice to coat underside?

Postby Simba » Thu Mar 11, 2010 3:22 am

POR15 works great. I've used it on many restorations, and the AT. It won't chip at all providing it is applied properly to a reasonably clean surface. I have stuff that has been blasted by gravel for two years and still looks new.

First, remove all grease, oil, debris, etc. Use a good degreaser followed by brake cleaner and give everything a good scrub with a plastic bristle brush.

Then, if you have surface rust (e.g. not something that needs to be cut/welded), hit everything with Metal-Ready as directed.

Once prepared and cleaned, LET IT DRY. Stuff the car in an enclosed area with a heater and keep it above 50 degrees for a few days at least. Above 70 is better. Be careful that your fuel tank is not completely full as it will expand with the higher temperature.

Once dry, paint as you like. Again, I would not apply the paint below 50 degrees. Above 70 for application and curing is ideal. Be sure and wear gloves and cover up well, POR15 will stay with you for a while.

POR15 does not need to be primed, sealed, or anything else of that nature. It works better than most sealers on its own. You may want to use several coats in areas that will see a lot of road gunk.


Doing the underbody and fender wells is a very good way to keep those respective areas happy. I would personally not used rubberized paints as they can trap water if damaged and accelerate rust.

Specific to the AT, one thing you REALLY want to do to prevent rust is completely remove the rear hatch panels, rear seats and associated panels, and speaker boxes. That will allow you to closely inspect the rear wheel well seams, which are an extremely common trouble area for rust. Coat the backs of the seams via the access holes in the body and you'll be rust free for a good long while.

It's also wise to pay attention to the lower fender area directly behind the wheels. Again, you can access both sides through the access holes-- directly below the jack bracket is the area I'm talking about. Get a bunch of POR15 in there and you're unlikely to have rust issues.

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Re: POR15/Rust Bullet advice to coat underside?

Postby toayoztan » Thu Mar 11, 2010 6:59 am

Simba, thanks for the write up, very nice to have a step by step.

One question though, would you recommend getting the OEM coating off? If not, that would be great. If so, that will suck, but I guess I'll need to do it.

Bryan
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