[cutlas]

Hay guys, my car had the underside, subframe, and firewall coated with POR 15 by the previous owner. It was done with a paint brush and left brush marks on the cowel. I would like to paint this chassis black but am not sure if I need to apply epoxy primer over the POR 15 or if I can apply the paint over the POR 15.
any help would be appreciated.

Joe.

[ITSBACK]

Doesnt POR 15 make a primer to go over in order to top coat. Check Eastwood.

[69Customs]

Should be able to sand smooth and paint over it. Sanding is suppose to give it a mechanical bond. I have found that instead of using their primer that self etching primer can be sprayed on top of it without sanding and will bite into it. Then that can be top coated. Regular primer will just wipe off if not sanded first. I think it has something to do with the acid mixing with the epoxy enamel on the self etch stuff which they tell you not to use self etch primer under epoxy enamel but it works for me over the POR15.
May want to do some sample testing before you go too far.
If it was me I would sand out any brush marks where needed, Bug bomb with good self-etch primer, then paint.
It held up on my rims which were sandblasted, phospated, then POR 15. Primed with self-etch primer, and top coated back in 2003 cause I was too lazy to sand all the little nooks and crannies in the rim.
Let us know how you make out.

[rustedgoat]

POR is such a hit or miss if it stays on or comes off in sheets. In highly visible areas I would sand it off and epoxy prime and get the finish you want. If when sanding it starts to come off in flakes then you know the bond just isn't there.

[sts]

<POR is such a hit or miss if it stays on or comes off in sheets.> The reason I would strip every molecule off.

[61-63]

Originally Posted by sts

<POR is such a hit or miss if it stays on or comes off in sheets.> The reason I would strip every molecule off.

x3 what he and rustedgoat says. I've dealt with enough POR15 on items now I would sure get it all off and see what you have underneath.

[cutlas]

Thanks Guys.
I guess I have some sanding to do.
I will let you know how it works out.

Joe.

[ITSBACK]

I used Bill Hirsch miracle paint which is the same as POR-15. I did 2 coats. First coat dried and sat for week. I sanded it by hand, oainted inside the chassis with Eastwoods paint for inside the chassis which looks like green primer. Sanded any drips or high spots that ran out and did a second coat of BH. If you use the Eastwood internal paint it has a long thin tube you feed into the chassis and spray as you slowly pull it out, remember it sprays out of any little hole in the chassis and drips out so dont use ot last or have the chassis close to anything you dont want green paint splattered on.

[mikes2nd]

This is why I like silver bullet better... much better. I only use POR15 on stuff I can reshoot.

I silver bulleted the whole car, then sprayed undercoat paint on the bottom(not the thick heavy rubber crap). Never put rubberized undercoating on your car.

http://www.rustbullet.com/Products/A...Automotive.asp

[ho421]

Originally Posted by mikes2nd

This is why I like silver bullet better... much better. I only use POR15 on stuff I can reshoot.

I silver bulleted the whole car, then sprayed undercoat paint on the bottom(not the thick heavy rubber crap). Never put rubberized undercoating on your car.

http://www.rustbullet.com/Products/A...Automotive.asp

Can you expand upon non-rubberized "undercoat paint"? I too have used rust bullet with success but as the others have said above, it either sticks or comes off in sheets and IMO the same would apply to POR15 and Chassis Saver. The key is prep. I intend to use the metal impregnated (silver) rust bullet on the underside but intend to take a few extra precautions. I'm going to remove all flash rust and scale with a cup brush on an angle grinder, followed by a cleanup using a prep solvent (GON) and finish by etching the underside with POR15's Prep-n-Ready. After I coat with Rust Bullet, I want to cover that nasty silver stuff with "something" black. So, I'd be interested in knowing what would be a good undercoat paint to topcoat the Rust Bullet.

[mikes2nd]

i used eastwoods rust encapsulator over the silver bullet.

I wonder about lizard skin though...

[paint guy]

I am wondering why there are so many people who use MDI (methylene diisocyanate)type products (POR, "rust encapsulator", "Silver bullet",etc.) rather than removing rust, cleaning the substrate, and then applying epoxy primer? This is the tried and proven method in the automotive industry, heavy equipment, railroad, military, etc... Somebody please educate me as to why one feels that this type of paint is better.

[61-63]

Originally Posted by paint guy

I am wondering why there are so many people who use MDI (methylene diisocyanate)type products (POR, "rust encapsulator", "Silver bullet",etc.) rather than removing rust, cleaning the substrate, and then applying epoxy primer? This is the tried and proven method in the automotive industry, heavy equipment, railroad, military, etc... Somebody please educate me as to why one feels that this type of paint is better.

You already know the answer; it is a lot more work to do it right that to spray the POR15 type junk.

[mikes2nd]

Originally Posted by 61-63

You already know the answer; it is a lot more work to do it right that to spray the POR15 type junk.

well yeah it is and yes the classic response "dude Im a pro, i would never use a rust encapsulator"...

Well.. I think its kind of a toss up, and it an arguement that can go on forever.

I think many "pro's" argue, you should never try to paint your car yourself(its good for their career of course to discourage home painters). Multiple coats of epoxy paint lends itself to a paint shop... Someone using a home sprayer and one coat defeats his income. So there is some biase there.

But epoxy will work, and I think something like Rust Bullet will also. We have all tried Por15 but we put it on a non scuffed greasy frame and it flakes off. I shot rust bullet one a blasted body and it worked great. I think POR is much more "finicky" than rust bullet. Will it work better? possibly(see below). But for me spraying rust bullet on worked great, looked great.

I personally think por15 is meh...(application wise), but thats because you can't simply apply it over anything and no uv protection.

Eastwoods Rust encapsulator goes on easy also.

http://www.eastwood.com/por-15-vs-ru...arision-part-1

http://www.drjing.com/Mini/BLOG/SideBySide.htm

Here is Rust Bullets "answer" to epoxy primer being better.

How does Rust Bullet compare to an Epoxy Primer?
An Epoxy Primer is not an anti-corrosive coating and will not furnish the protection provided by Rust Bullet. Rust Bullet coating penetrates and dehydrates rust then forms a protective shield that defends the surface against corrosion and abrasion for many years. If an epoxy finish is desired, and the existing surface is an epoxy finish, scrape off any loose rust and epoxy coating, rough-up the remaining tight epoxy with 100 3 grit sandpaper prior to applying Rust Bullet, then re-apply the epoxy coating over the final coat of Rust Bullet. Please note: For best results, the surface should be prepared down to bare metal. Rust Bullet works best when it is in direct contact with rusted or clean metal.

How does Rust Bullet compare to an Epoxy as a Bridge Coating?
Rust Bullet provides excellent, long lasting, low maintenance protection for bridges and other transportation infrastructures. Rust Bullet is a high performance coating that has been awarded two (2) United States Patents for its two (2) unique technologies for rust and corrosion control. Generally Epoxy coatings are much thicker, plastic type coatings not intended to control corrosion. Epoxy coating applications are more complicated and labor intensive than Rust Bullet’s application. Other paints and coatings, including Epoxy coatings, require extensive preparation using a variety of techniques such as, sand blasting and collecting, needling, heavy scraping and chemical treating. Added to the high cost for these preparation procedures, costs for the containment and disposal of the waste created by these extensive preparation procedures, in order to comply with EPA (Environmental Protection Agency) requirements, often make these costs far greater than the initial cost of the product. None of these extensive preparation procedures are needed for Rust Bullet, consequently saving down time, labor, and cost. An Epoxy topcoat can be applied if desired.

This is the sales pitch but there is something to be said about what they are pushing, its not all bs(anti corrosive protection). There is none in epoxy primer... period. and they are more labor intensive.

Myself I have seen great results with spraying Rust Bullet right on a bare metal... Its thick, its cheap(well...) and its easy to spray and takes top coats and body filler fine. No bubbling, no issues at all, slap it on, go nuts.

If epoxy primer worked so well, why would all our cars be so rusted out. These cars were metal etched and primer sealed... they rust when you look at them funny. The factory doesnt mind your car rusting.

The whole arguement about "factory" doesnt use it is a joke, the factory could make your car last 100 years if it wanted to, but its a good thing when your car rusts out after a while. Back in the 80's the car makers made them practically fall apart driving off the lot. Now car makers were forced to compete with the japanese so your body panels are great. But after 5 years go look under the car, your frames will be rusting if your in the snow belt. That didn't have to happen, your car maker made a decision to ignore that bolt and save some money by not rust proofing it correctly.

Heavy equipment does use "anti corrosion" primers

I know modern epoxy primers are better now of course(zinc included is even better)... so basically I think its a toss up, they both have their pro's and con's. My choice is to rust bullet a car with a gun twice, call it a day.

[dataway]

3M or Dupont ...forget which, still sells an "asphault" based undercoat in a spray can. Not cheap, and not common. I get it at the local NAPA where I usually have to order it. I also have a can of (again expensive) brush on asphault based undercoat that I got at my GM dealer. Had no label or anything, just a silver can, parts guy said that techs used to to patch up undercoat after making repairs or replacing parts. I use both these products on my new vehicles when I buy them.

The spray on stuff has the appearance of rubberized undercoat when it goes on, but after it dries it appears much more of an oil or parafin based product, black, not as sticky as old school asphault undercoat, but not "clean rubber" feeling like the rubberized stuff. I've got some down in the shop, I'll try to remember to get the number off it.

The canned stuff is great, goey, old school, oil based undercoat, very thick.

JohnnyB

[paint guy]

Mikes2nd: The sales pitch you posted about Rust Bullet , and your post, contains some incorrect information. Your statement "there is none in epoxy primer" (corrosion inhibitive pigments) is simply not true. Likewise the first statement in the Rust bullet literature: An epoxy primer is not an anti-corrosive coating... This statement is total and utter BS. BTW, this is NOT opinion, it is fact that can be supported by reams of salt fog and water-immersion data, recommended corrosion control procedures published by N.A.C.E ( National Association of Corrosion Engineers), published specs by various D.O.T.s (bridges), the U.S. military, John Deere, G.M., Ford, Chrysler... want me to go on? And your statement " the factory doesn't use it" is the real joke. Have you noticed how much better corrosion control in transportation is nowadays compared to 30-40 years ago? And do you really think that engineers for steel bridges would engineer in pre-determined obsolescence? Please refer to the I-35 bridge collapse in Minnesota a few years ago.If anyone cares to send me a sample of POR, Rust Bullet, or Rust encapsulator, I will spray them and various epoxy primer formulas on std. paint panels in a laboratory, put them in a salt fog and water-immersion cabinet, document and publish the results on this forum. Any takers?

[61-63]

I've got a '64 GP chassis outside my shop right now that I am in the final stages of parting out and the POR15 (I'm pretty sure that is what it is) is coming off of the frame in sheets due to rust creeping between the frame and the coating. I cannot know this but I think if a person took something down to bare metal and put one of those coatings on it would probably be OK. But that is not what the manufacturers of those products say to do; the tell people to knock the flakey stuff off and spray the POR or whatever on and you are good to go. That might work too possibly if a perfect covering was accomplished and no moisture ever got in between the coating and the metal. But that apparently never happens and I have seen it over and over now where the POR15 type product has rust going on underneath and starts letting go.

I am not a professional and I have taken lots of shortcuts, most to my later dismay, and I've finally decided it is just better in the long run to do it right rather than have to redo it down the road.

Someone on the Autobodystore site did a test once on all of the POR15 type coatings and as I recall the Eastwood product turned out to be the best one at that time. But that was several years ago and their product's formula may not be the same now. Plus it would be interesting to see now what those same test panels look like after several additional years.

[ho421]

I should know better to chime in on this as its a topic that has been discussed before. For starters, my chassis was sandblasted with three shots of PPG DP90 epoxy (lead-based). That was (gosh) 5-6 years ago and although it sits in my shop, it looks as good as it did when I shot it. I'm totally sold on epoxy and when I sand the body down, I have no intentions to use etching primer. Epoxy all the way. But, I have also taken advantage of using an encapsulator (Rust Bullet) on internal areas. For example, I had to completely refab the inner rockers on my b-body and the insides of the inner and outer rockers were cleaned, sanded, etched and encapsulator (bullet) applied with success. I tested this product out and on smooth or surfaces that are not properly cleaned and etched it sheds like paper. I'm no expert but I'd expect the same to occur with an epoxy on improperly prepared metal. I intend to use rust bullet under the body above and around where the perimeter frame meets the rockers. Why? Because I can't be 100% certain that i've removed every tidbit of rust from this area. There's some pitting in areas and if I could have bought repop'd floor pans I would have done so but these parts are just not available. I have no rotisserie and no means to move it out of the shop to sandblast. Anyway, once this area is hit with an encapsulator, the entire underneath will be shot with epoxy and then with something else to provide durability. Maybe Endura black since UV won't be an issue. I respect everyones opinion on this forum. Whether you are a novice or an expert, you make this forum tick and I thank you.

[69Customs]

I use Por15 as directed when possible removing rust and applying to bare metal with the phosphate as directed. I never spray as that is not recommended. I used it in the inner truck lid when I had the lid off, Cleaning out as much inside without taking it apart. I then poured POR15 into it with it upside down and swished the trunk lid so it came out all small drain holes in corners. WHY? Cause I can't get into sand surface rust out and paint. I wanted all inside creases to fill with it as it is a moisture curing paint. The more moisture the harder it gets. I figure it will block any air or moisture from getting to any surface rust and seal it from going any farther. Regular paint breathes and can let moisture thru.
So I figure something to seal light surface rust is better than nothing. Plus POR15 you don't have to mix like epoxy enamel.
That's why I use it and have had good results.

[ITSBACK]

Bill Hirsch recomends painting in the garage on a rainy night for optimum curing.