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Mon Jan 07, 2013 11:01 am

Thanks for the advice!
I don't want to hijack the thread, but here's my quick take on OSPHO and my history of such products.

I've been a fan of "Rust Converter" the milky stuff that dries purple black for many years. I treated my old stretch in 1996 on some majorly rusting floors and in 12 years of use in California like climates the rust never returned.

Eventually I heard of POR 15, I bought a kit but it looked complicated and thick and so I never tried it out. It's still on my shelf.

Then a few months ago I called up American Metal Cleaning in Portland since I was considering having them dip the whole DOKA so I could start with clean metal.

http://www.americanmetalcleaning.com/automotive.html

I was concerned that these products would be so hard that they would not come off in the cleaning tank. The guy assured me that rust converter was no problem but he suggested OSPHO since they've had great results for a long time and it's thinner and so penetrates better. I then asked "what about POR 15" and the guy just laughed! He said POR 15 was so poor it came off with a power washer before they even dip the vehicles.

So there's one man's opinion, a guy who cleans these products off every day and so I assume has some good ideas about it.

For good VW content, you can see a Bay window getting dipped at American Metal Cleaning in this video. http://www.youtube.com/watch?v=tRn-cQp2VqE Dipping starts at 1:00. Now that ought to clean out any seam rust!

Mon Jan 07, 2013 11:32 am

Otmar, I will back up AMC's claims/support for OSPHO and POR15.

I have NEVER been a fan of POR15. I have used it a couple of times and regretted it (one of the times it was used on the restoration of fairly rare '69 Camaro Z28 upon the customer's request. The areas where POR15 was used had to be redone eventually due to failure. I have never experienced a come-back from the use of OSPHO) . I have used OSPHO a number of times and have always been very happy with the results.

One note about OSPHO. Protect your concrete from it. It contains phosphoric acid which severely etches concrete.

As for a process, I recommend the following:

1) Mechanically remove as much rust as possible. Sandblasting, wire wheel, grinding, sanding, picking, etc.
2) Treat the remaining metal with a phosphoric acid based product such as OSPHO. Different products like this have different instructions for use, so follow the instructions.
3) If any welding or bodywork needs to be performed, now is the time to do it.
4) If any pitting is present or any bodywork has been performed, use filler primer now.
5) Apply epoxy primer
6) Apply seam sealer to the exterior seams
7) Paint
8) Treat the inside/backside of the seams with wax, seam sealer, etc. Anything that seals the backside of the seam from moisture intrusion is acceptable.

There are variations on this list and some basic details of the specific procedures are left out, but if you are in doubt, done properly the following this list will yield great results. Traditional rubberized undercoating isn't a very good choice unless seam sealer has properly been applied to the seams prior to the application of the undercoating.

Mon Jan 07, 2013 12:13 pm

Christopher Schimke wrote: One note about OSPHO. Protect your concrete from it. It contains phosphoric acid which severely etches concrete.

I learned that the hard way! I have a sweet diamond polished concrete floor, but not where I was working on the Stretch side seam anymore. I did get a box of baking soda on it pretty quick so it's not that big a spot, but still it's not so pretty.

Thanks for the step by step!

Mon Jan 07, 2013 1:29 pm

Por 15 is a type of "top coat" cover..moisture and oxygen will still find a way to get in there and continue to rust

Mon Jan 07, 2013 3:30 pm

As for a process, I recommend the following:

[list]1) Mechanically remove as much rust as possible. Sandblasting, wire wheel, grinding, sanding, picking, etc.
2) Treat the remaining metal with a phosphoric acid based product such as OSPHO. Different products like this have different instructions for use, so follow the instructions.
3) If any welding or bodywork needs to be performed, now is the time to do it.
4) If any pitting is present or any bodywork has been performed, use filler primer now.
5) Apply epoxy primer
6) Apply seam sealer to the exterior seams
7) Paint
8) Treat the inside/backside of the seams with wax, seam sealer, etc.

A little out of sync, but close.
Do all of the body work, weld sand blast, whatever, then treat the metal with Metal Prep, then do the spot putty or bondo treatment, load up the seams, , acid etch prime, sand, urethane prime, sand, & refinish would be the correct process.

I surely wouldn't be priming prior to sealing up seams--your eliminating the grabber's for the seam sealer to hold onto--
Never would I add any primer of any kind without acid etch priming the open metal first.

Mon Jan 07, 2013 5:11 pm

Terry Kay wrote:

A little out of sync, but close.
Do all of the body work, weld sand blast, whatever, then treat the metal with Metal Prep, then do the spot putty or bondo treatment, load up the seams, , acid etch prime, sand, urethane prime, sand, & refinish would be the correct process.

I surely wouldn't be priming prior to sealing up seams--your eliminating the garbber's for the seam sealer to hold onto--
Never would I add any primer of any kind without acid etch priming the open metal first.

As far as treating the metal with OSPHO (or similar product) prior or post bodywork (referring to metal work, welding, etc., not any body filler work), I prefer to do it prior, but post works fine too I suppose. Just my preference. The reason that I prefer to apply it prior is because OSPHO works great as a pre-weld cleaner and kills any rust that may be encountered prior to welding. That makes for a better weld....not welding over rust I mean.

I'm not a big fan of acid etch primers, but some people are. In my opinion, the application and use of OSPHO and epoxy primers is a better way to go.

In fact, PPG does not recommend using their etch primers over any other metal treatments and not over media (meaning sand, aluminum oxide, etc.) blasted metal.

And finally, yes, I do in fact think it is best to use seam sealer over primer. If you seam seal over filler primer, it's best to make sure the primer is sanded to its final state (600-800 grit for most applications). However, seam sealer can be applied directly over epoxy sealer primer too. It bonds to both really well, provided a good quality seam sealer is used. In fact, epoxy seam sealer over epoxy sealer primer is almost impossible to remove due to the chemical bond between the two.

In my opinion, seam sealing is near the last step. If I seam seal over sanded filler primer, it is the very last thing that I do prior to applying an epoxy sealer primer. If I have to seal over the top of epoxy sealer primer, I will spray just a light coat of epoxy sealer over the top of the seam sealer (after the seam sealer is applied and cured of course) just to ensure that the paint has a good, even base to bond to.

As I said before, different processes for different people, but if someone has no clue one way or the other, the process as explained is a proven route to take.

Mon Jan 07, 2013 6:17 pm

3-M recommends to apply the 8115 on clean & dry sheet metal directly, not over any primer.

Dupont recommends using acid etch / zinc chromate primer directly to the clean area to be locked down & sealed.
Sanded & then primed--you'll never have anything lifting after the application of the zinc chromate.

Urethane primer's are far superior to epoxy based primer's in that they take more abuse, and are much easier to prep prior to the top coat, and if you treat the sheet metal as you would aluminum or stainless, (which you have to use Vari Prime) you'd never have any lifting, primer, or top coat failures.
Epoxy prime all by itself is not a suggested or recommended for a peliminary primer for either one---the paint would blow off in sheets.

It has no acid etching properties.

Aluminum automotive & truck,as well as stainless steel requires zinc chromate self etching primer prior to doing anything else--I treat sheet metal the same way.
I 'm much rather be certain whatever I have the Vari Prime on will stay put---

Mon Jan 07, 2013 11:57 pm

Here's another way to get all of the rust outa the seams, for those of you who don't have access to an air compressor, or don't want or care to have one.

A stainless tooth brush sized wire brush, and a bottle of muriatic acid.
( I will tell you guys right up front that this process will screw up more of the paint on either side of the seam than the spot sandblaster--)

Tape off either side of the seam,the width of the mini wire brush, and along with it dipped in the muriatic--brush away.

It'll get all of the rust outa that seam faster than you can blink--plus it'l get all of the rust out of any pits in the metal you may have.

Have a mixture of 1/4 of a cup of baking soda ,mixed into a quart of water to neutralize the acid.
Let it dry.
Give it a quick wipe with Metal Prep, and seam seal it with something.

I use this cleaning process prior to leading panels.
filling in the seams on a chopped top--frenched in tail lights, whatever.

It's important to get the panel sqeaky clean as you can prior to using lead so it sticks.
Muriatic works the best.
You just have to remember to neutralize the acid when your all done.

Tue Jan 08, 2013 7:09 am

Scared to post again with all the stern talking but I must...

What's OSPHO? I take it that its a rust remdy fro bare clean metal much like the POR15 product, which I have used with limited success.

I found it...

http://www.ospho.com/

Hmmn I wonder if its available in the UK.

Tue Jan 08, 2013 7:10 am

Dyno Soar wrote: Scared to post again with all the stern talking but I must...

What's OSPHO? I take it that its a rust remdy fro bare clean metal much like the POR15 product, which I have used with limited success.

I've never heard of it, either - but at a wild google-fuelled guess...
http://www.ospho.com/

Tue Jan 08, 2013 7:12 am

AdrianC wrote: Dyno Soar wrote: Scared to post again with all the stern talking but I must...

What's OSPHO? I take it that its a rust remdy fro bare clean metal much like the POR15 product, which I have used with limited success.

I've never heard of it, either - but at a wild google-fuelled guess...
http://www.ospho.com/ ..can be purchased from almost any hardware store..

Tue Jan 08, 2013 7:16 am

err... thanks.

Its exactly the same as Kurerust her in the uk by the all accounts.

Tue Jan 08, 2013 7:21 am

Sounds pretty much the same as Dupont Metal Prep, only probabaly a mail order item at twice the price.

The 5717 S Metal Prep can be had at any local Dupont automotive paint dealer, and is about 8 bucks a quart.

Wipe on, rinse with water. When it's dry it leaves a phosphoric acid etching in the metal.

Been around & used in automotive painting for a 100 years.

Good stuff.

dpcprd.asp.dupont.com/.../html/prodinfo/chromasystem/H-19298_5717S.pdf

Tue Jan 08, 2013 7:24 am

Dyno Soar wrote: Its exactly the same as Kurerust her in the uk by the all accounts.

In theory, yes, similar to Kurust - it "converts" rust into a solid and stable oxide layer, preventing further corrosion from developing. In practice, I doubt it - going by the positive comments about Ospho. Which, unfortunately, doesn't seem to be available over here in the UK...

Vactan's one that's available over here and gets positive comments, though.

Tue Jan 08, 2013 8:09 am

Terry Kay wrote: Have a mixture of 1/4 of a cup of baking soda ,mixed into a quart of water to neutralize the acid.

You just have to remember to neutralize the acid when your all done.

Many who have experienced products not adhering have forgotten this step.

Tue Jan 08, 2013 8:11 am

AdrianC wrote: ...Ospho. Which, unfortunately, doesn't seem to be available over here in the UK...

Vactan's one that's available over here and gets positive comments, though.

Or, right on cue and mentioned by a pro restorer on another forum, there's this stuff... Omnicote.

http://www.anti-slip-paint.co.uk/omnicote-litre-250ml-rust-converter-black-p-132.html

Tue Jan 08, 2013 9:27 am

Clearly what is available varies by your location.
I used to mail order Rust Converter, but now I go to my local True Value hardware store to pick up OSPHO, $9 for a large bottle.

Tue Jan 08, 2013 4:27 pm

Goods info here, so I have a question for you seam experts.

I did my seams a couple of years ago. Por 15 inside, sand blast followed by a rust inhibitor (brand?) outside. Used a good pro seal sealer from an auto store. Good rattle can (paint match.com) primer & paint & clear coat on top. No rust has reappeared, but the seams all look black & dirty. Washing & scrubbing doesn't help. What's the deal?

In addition my paint job doesn't have the shine of the adjoining panel. On this aspect of the problem I can't figure out if I applied the paint and/or clear coat too thin or rubbed out the clear coat too much or not enough.

Any advice from a paint expert is gratefully received.

Tue Jan 08, 2013 6:13 pm

This is what I'm going to try out for my seams and re-finishing. Any thoughts besides spend money on a real paint job? Please keep in mind all I want out of it is a bargain refinish to halt the body rust and hopefully look half decent and last a while without me worrying about pushing a $$ paint job through logging road bush. I have a friend at a local chemical/paint store who can get me their stock at cost so I'm working with what inventory they have to keep the budget low (this way I have a bigger budget for phase 2 to swap my "better" engine in and freshen up a few things...)

1. Wire-wheel the rust and sealant from exterior seams. The wheel pictured seems to do a really good job without grinding away steel when I did a few seams as a test. I will also remove the panels and clean up the interior seams with the wire wheel/brush.
2. Rust converter on the exposed metal and cleaned rust, inside and out on seams.
3. Body work (couple holes to fill and small dents to try and straighten).
4. Seal up the seams with spray-on sealer. Rubberized, flexible, paintable and rust-inhibitive so sounds good right? (I hope!) I plan on masking and spraying the seams with as many coats as it takes to build the seam up to flush, with the idea that the more liquid spray-on stuff will penetrate deeper into the seam? Then the same spray-on sealer will be applied to the seams from the inside in multiple coats.
5. Sanding prep and Etch primer
6. Paint upper with Rust inhibitive Polyurethane:
http://www.insl-x.com/viewProd.asp?prodID=44
7. Paint rocker panels, fenders, front with truck bed liner:
http://www.herculiner.com/

Some of the products I'm currently using:

Results of the wire wheel with rust converter on a rusty seam:

Anyway... think it will do the job? Any thoughts on the Acid-etch primer going on over the rust converter or the spray-on sealer? I got an acid-etch with the thought of priming over a combination of metal, old paint and body filler and thinking this would hopefully bond well to everything but perhaps I should be going with an epoxy primer like Chris suggested?

Thanks,
GT
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Tue Jan 08, 2013 7:39 pm

geo_tonz wrote:

Anyway... think it will do the job? Any thoughts on the Acid-etch primer going on over the rust converter or the spray-on sealer? I got an acid-etch with the thought of priming over a combination of metal, old paint and body filler and thinking this would hopefully bond well to everything but perhaps I should be going with an epoxy primer like Chris suggested?

Thanks,
GT
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You know, each paint system has its own quirks and requirements. Companies such as PPG do not recommend putting etch primer over any other metal treatment. While I don't think it is necessary to use the etch primer, if you really want to use it, I would call that company's tech line and ask before doing so.

In my opinion, using a metal prep type product on bare metal, followed by filler work, then a coat of urethane filler primer (properly sanding after dry) followed by a coat of epoxy sealer primer (such as the DP line from PPG), then paint is a far superior way to go, but that's just my preference. You are doing things that are somewhat out of the norm, so you may have to come up with your own methods here.

I'm not so sure about building up the sealer so it is flush. I feel it would be better to mask off the seam right at the 90º bends in the sheetmetal (on either side of the seam) to protect your surrounding bodywork, paint, etc., then apply your sealer, using your finger to work it into the seam, then making a full, smooth pass with your finger to give it a nice concave radius. Then remove your tape and give it one final pass with your finger wetted with either spit (seriously) or solvent to smooth out the little ridge left at the edges of the tape. Then when the sealer is dry, paint away.