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Given this former Cali car is coming up on 50 years and probably not always taken good care of, I am lucky to have this level or rusting. I went after it with Ospho, wire brush and clean rinse.

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Will be applying POR 15 to this area.

Question: my gut tells me the well adhered tar is sound and is not hiding any rusting.

Agree, looks good

Looks pretty good but playing devils advocate - an oscillating multi-tool with a scraper blade takes the tar off pretty easily.

Or dry ice.

That remnant tar looks pretty ratty, just remove it and replace it.

AA has an original floor tar looking kit, there are other solutions.

Por 15 is trash.

You’re on the right track but once it’s all clean then epoxy primer then body color. Por 15 is well marketed junk just like k&n air filters which is another rabbit hole.

I have wondered that for years. A year or so ago I bought a couple pint containers and go between POR or basic oil based DTM from the corner hardware store. Funny how us Americans are easily sold a bill of goods by the marketing folks. I have some epoxy primer that I am using on the entire body after paint removal.

Does anything stop the rust in it's tracks, my thought is to keep it sealed and dry.

Mar-Hyde is a first rate rust conversion product. Mar-Hyde can be sanded and painted. Apply the MH with a cheap disposable foam brush. Wear disp gloves when using this product. It will leave dark purple stains if you get it on your hands.

and definitely replace the original factory floor pan tar and paint the car's color

Been there, done that, won't ever do it again ...

Here’s my preferred epoxy primer solution - no mixing (other than puncture the 2nd chamber), no spray gun to clean. Lasts 3-4 days in can after activated. Available in multiple colors (grey, beige, black).

Great for small areas like you’re dealing with.

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More devils advocate:

IMHO POR 15 has its uses.

Low buck, low quality, heavily rusted stuff you don’t care about too much but where you are wanting it painted is where I tend to use it.

POR15 is a moisture cure urethane product largely for Paint Over Rust (POR) as the name implies. It depends on the adhesion of the rust to iron to form its bond to metal while sealing the rust underneath. It does not stop rust under that coating despite what is implied.

When used on bare metal, it doesn’t form as strong of a bond as epoxy primer. The instances of POR15 peeling off in sheets from bare metal (smooth or sandblasted) are well documented. This always gets blamed on prep, but is the nature of the beast (moisture cure) paint which was not designed to be used as “primer”. Likewise, once cured, other paints don’t like to bond to POR15. And per the POR literature, POR15 isn’t UV stable so it needs to be topcoated if exposed to UV. But . . . Other paint doesn’t stick well to it . . . So there’s that little problem.

I don’t think highly of POR15, but have used it on occasion, I thought I’d outline why it isn’t the right product to use for OP’s proposed purpose.

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About 10 minutes and yes there is rust under what appeared to be well adhered tar.

Yup!

In a plain steel, pre galvaneal, pre e-coat world, whatever humidity was in the plant is what got trapped between the tar, and paint.

This is why there is no such thing as a rust free 914 and why it is said that 914’s came from factory with rust.

Well on your way to not being DAPO. Now back away from the hardware store DTM.

You need to use an Awl and push in the areas that have some rust. On my 1969 build factory 6, when I removed the tar from the top of the pan and it looked OK but was not at all in the lower parts( recessed areas) of the pan under the seats. Southern California car garaged most of its life and in a garage for sure from 1986 on. There was no rust anyplace on the rest of car that we could find but I am happy that I changed out the pans so it would be perfect. I put factory tar on from George at AA, but PMB Performance wanted to put a different kind of modern mat on with better sound dreading.

I thought it was going to be great right there on the pan but no. We had to go into it for the clutch tube fix so new pans. I am going to show you a picture of the hell hole (not) so you can see just how not screwed my car was.

Best Bob B
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I will go after all of the rusted areas tomorrow with an awl

Is there any 914 in existence that is really rust free? my $5. is NO

thanks all

I just ordered a few cans to try. My main problem with my restoration is keeping the exposed metal rust free till I can get a large enough area to make it worth my while with the spray gun and the 2k epoxy. I'd like to be able to do smaller areas when they are ready with epoxy once, and not have to strip off temporary, and expensive, etch primer. This might be the solution I've been looking for. Thanks @Superhawk996 .

I think you’ll like it. @friethmiller

I struggled with same problems when working in Midwest humidity. Seems expensive but the convenience and not having to mix, clean gun, etc. offset all that.

It holds up to nearby heat very well when welding near it.

Good to know! I'll post about it in my build thread next time whenever it decides to warm up again here in Texas.

Almost passed the awl test, one small (less than 1/4" dia.) is all that I could get. Also, the poorly adhered POR is gone. It gripped to the rusted areas, but not at all to the clean surfaces.

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Another option to the POR 15 is Rust Bullet.

Used it on my car, on the undersides and inside floor. But did not paint it over rust. cleaned , sanded or blasted the areas first then two coats of rust bullet followed by two coats of epoxy primer and finally two coast of PPG single stage color.

Have not experienced any lifting.

Check post #22 in my build thread below.

Or use one of these and get it squeaky clean.

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Mine is for sale if interested.

Reading this thread has given me a case of the “what if’s?”

I felt disappointed when I got my first look at my car’s floor pan interior given the restoration and repaint it had. I’m unclear if it’s original or not, but it wasn’t what I was expecting. I might take & upload a pic for comments sometime …

But for now I’m thinking about removing the black coating to see what the floor surface is like.

So my question is does anyone have experience with a brush on epoxy primer they’d recommend?

TIA

From what I know ALL 914's have rust somewhere, but given they have been around for 50 or so years says something. The way I look at is, if I can do my best to get things in order and enjoy while I can it's a plus. In 50 years I will be 121. the hope is to pass on a sporting machine to each of my 6 grandkids. Today I am 5/6 of the way there

I recently started using a brush on epoxy primer from Eastwood. Only time will tell the story.

I used Loctite "Extend rust treatment" which turned flash rust into a black hard protected finish. Treated the inside of the center tunnel with a very long handled paint brush, worked very well.

Any two-part epoxy primer will work. I just use a disposable chip brush. I've been using the Summit epoxy lately as the price is right and I like the product. It mixes 1:1. I buy it in gallons, though it may be available in smaller quantities. Two coats to cover any brush marks.

Excellent, that’s what I was hoping. Thanks guys

Likely the POR15 didn't stick to the clean surfaces because they weren't prepped properly. I seem to be a regular POR15 apologist, but I'd bet that most don't do the requisite prep work before applying it. I did my floor pan 17 years ago after removing all of the surface rust and it looks the same as the day I put the stuff on. At the same time I also did my rocker panels (inside and out) thinking I'd end up re-stripping and painting them later when I got the car repainted (hasn't happened yet ), and they've held up 100%.

I did not use their "Metal Prep Etch". Suppose any product will not work if the manufacturers instructions are not followed. I did use Ospho on the rusted areas and POR 15 appears to have bonded well in those places.

I think BITE is the key phrase here. What will grab steel with good adhesion?

I love epoxy paint. Dry ice will actually work in getting the tar off. Convert the rust or better yet sand it off. Then epoxy. It is expensive but I like the dplf epoxy from PPG.

My gut tells me sandblast is best, but too messy for this application. When blasted a decent profile can be obtained to grip the first layer of primer. Ospho is probably the next best

If using Ospho be sure to rinse / neutralize it thoroughly before primer. The directions on the Ospho bottle are not pertinent to automotive paint systems.

I'll look into eastwood and summit for the brush on. I'm about to start the same, my 356 body guy just uses rustoleum and has good luck with it. It's inside the car and has good adhesion plus I'll put insulation over it anyway.

Mine passed a very preliminary awl test. I’ll get rid of gooey black stuff next to see what’s underneath. Then treat with Evaporust, cider vinegar or sanding as needed and then epoxy primer & paint.

1/19/24 addition: With what I’m now seeing in these recent shots, it looks like there’s a lot more exploring and work (scraping, sanding, rust removal, (and I hope! ) no metal replacement, epoxy priming and painting, etc needed to make my car right.


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From the Por-15 Tech sheet:
POR-15® Rust Preventive Coating is designed for application directly on
rusted, sandblasted, and seasoned metal surfaces.

It could be more clear. What is seasoned metal?

From my experience, if you don't have rust pitting, or any tooth in the metal, POR-15 won't adhere well. If the area is rusted, then it adheres just fine. One thing you can do, if you have an area that has been weakened by rust pitting on one side, but not enough to warrant cutting it out - Put down a coat of POR-15, then lay down some fiberglass cloth, and fill the cloth with POR-15. This is very strong.

I’ve gotten confused with all the discussion about hardware store paint, brushes, and now we’re back to fiberglass.

Was this thread how to avoid DAPO or how to create DAPO?

Definately DAPO, if a little fiberglass is good, more is better:
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Your average 914. Seasoned for about 50 years.

I would guess seasoned metal has been treated by their "metal Prep'" as part of POR's system.

Must admit though, I have never heard of the term seasoned metal. It could mean many things

Kinda like treated metal … I took my car to Dairy Queen

The only seasoning of metal I know about is in reference to cast iron cookware.

There are so many alternatives to POR.

I'm glad to see the OP taking it to bare metal, removing (not 'treating') the rust, and applying the proper coating, epoxy primer. Absolutely, positively the best (and only, IMO) way of doing it.

Their Metal Ready product degreases and 'etches' the metal to allow POR15 to adhere to it. There are of course other products that do the same thing. As with any kind type of paint work, prep is key.



Please don't do this.

Please, this is a good sign of a ...... well you know

Perhaps I wasn’t clear. Sometimes people get scared into thinking they have a junk car, when it really can be fixed. I remember long ago some advice I was given by someone who told me my car was not worth fixing on account of some visible pitting in the hell hole area. An in depth repair was required but nothing like needing a new chassis. You can take your whole chassis apart spotweld by spotweld at every sign of minor rust, which is in many cases economically unfeasible. But this is also about knowing when to stop cutting. Major rust, yes, cut it out. Then weld a new panel in. But there are instances where, for isolated pitting, one might prefer to keep the original metal in place. Now, you have to use your judgement of course, and know which portions of your chassis are load bearing, and study the reinforcement. Typically, one needs to follow the tech sheets, which , as I pointed out, POR 15’s is vague. These products, and even epoxy primers can be tricky. Some products are DTM, direct to metal. Others require etching to give a mechanical tooth. Coating any bare metal, new or old is essential. But each product should be judged only after following the tech sheets. I would never apply POR-15 to new or smooth metal, because it can flake off.

This thread has become really interesting to see where people draw the DAPO line.

For me DAPO is more or less defined by “solutions” that defy logic - like the photo I posted from my chassis where some idiot (not pulling punches for the sake of kindness) laid in 1/4” of fiberglass and resin to “repair” or conceal a floor pan that needed complete replacement. I knew this to be the case when I bought the car. Unfortunately I’m not so sure about the guy I bought from when he bought it before me. He seemed to believe the car was less rusted than it was but eventually sold it to me at an appropriate price.

Where it crosses the line for me into bad behavior is when things are concealed that otherwise should be left exposed for the sake of transparency. Excessive undercoating is a great example of a benign product used by some to intentionally conceal rust, deep pitting, and pin hole perforations.

Your definition may vary.

When I was looking to buy a 914, excessive and fresh undercoating was a no-go for me. I'd rather a seller leave all the bad exposed so a potential buyer can make a fair assessment.

Too bad many sellers simply spray on "undercoating" to cover up any/all questionable areas. When buying any older machine requires a thorough inspection especialy if you are paying the long dollar

I agree the DAPO threshold is fuzzy. And I have to admit that some things I did when I was 17 I would now consider extreme DAPO. DAPO might also depend on the value of the car. Or its projected life span.

Maybe like porn, DAPO is something you know when you see it.

Second on Rust Bullet. I had no rust on my floor boards, however, it adhered extremely well and is almost a perfect match to my L96A silver.

We are all DAPO of the future.

Not sure if I agree, many of the restorations are making 914's better than factory