Wurth Stone Guard Gray - Drying Issue
 

Has anyone (besides me) had any problems with Wurth Stone Guard Gray (fuel tank paint) drying? If so what's the cure?

I repainted the bottom of the used fuel tank I acquired for my SC at least two months ago, using the Wurth product in spray cans. I put it up in a loft area while it was still tacky to get it out of the way. The storage area was dry and believe me it should have gotten hot enough to cure paint. When I pulled it out a bit ago it was STILL tacky, enough so it stuck to my jacket and clothes. So what gives here?

Any residual gasoline in the tank leaking? It would do just that to paint.

No, tank had been out a car and dry for some time. No gasoline residue in it at all. And this thing as been painted for at least sixty days, maybe ninety, and stored in an attic; pretty high temps and low humidity.

I have the same issue. I have plastic over the tank and don't have time to redo. The first coat was fine, but when I did the second coat, it felt dried. When put back in a car it got very sticky. Still in a car with plastic over. Need to remove and redo my tank. Not sure if its a paint and yes I used Wurth Stone Guard Gray.

ALMOST EXACTLY my experience. Needless to say I'm not a happy camper. Fortunately(?) I only did the bottom so I just may leave it sticky. Not decided yet.

I was hoping someone would have a solution!

Later - I tried excess heat, as with a heat gun, on a limited area with no success (i.e. no change). As this stuff is REAL sticky, as in leaving significant residue on my hands from just touching it, I have found that both Xylol and plain old gasoline cut it well. Since my tank is out of the car I can take it to a remote area outside the garage and use one of those to clean it - I hope. I also have access to a high-pressure steam cleaner which I may try first. Either way is going to be messy and a pain in the ass.

I also noted that the only place (which is most of the tank) where it did not dry was where it was sprayed over the original coating! Anyplace it was something else; bare metal (the strainer base and the inlet/outlet) or taped off it dried fine. It just doesn't like "itself," apparently.

I am not pleased with Wurth's product at all. I went to their website for possible tech support or to voice a complaint and I found no way for doing either; it's strictly sales oriented. Fat chance of that happening again with me! Whenever I get this stuff off I'll hit it with some black undercoating and be done with it, "originality" be damned!

Mine was somewhat sticky even two years after application. It looked pretty good but it was sticky

My tank did not dry either
 

I experienced the same thing very tacky using Wurth paint. My tank was removed from the car and cleaned well. Put the tank in the warm sun for about an hour. I then sprayed the tank in the garage. Some places it did dry somewhat but most of is tacky. It has now been three weeks. So, this past weekend I put the in the warm sun and it became more tacky. Sunday morning I put the tank next to my dehumidifier in the garage and ran the dehumidifier with the garage closed. Tonight I checked on the tank and it was much more drier and not very tacky. I plan on checking it again this weekend. Hopefully it will be dry. I really want to put this tank in the car. This whole pull the tank and paint has been a pain.

Went through this too. Discovered that Wurth StoneGard is very sensitive to how thickly it's applied (aerosol, not schutz gun). Did 2 moderate coats; still soft/tacky after 2 weeks. Stripped & tried again, this time 5 very thin coats w/~1 hour between coats -- success.

HTH

This is a very timely thread as I have the tank out of the car and plan to re-spray with the Wurth Stone Guard Gray soon and will try the five very thin coats technique. I may go with fewer coats because I don't plan to strip the old material, but simply spray over it. If that doesn't work out so well, then I'll strip it and start over.

Since the Gray product is available only in a rattle can now, I assume that is what most of you are using? Did this yield the correct texture?

And for those of you that the Stone Guard remained tacky, did anyone try spraying a gray topcoat over it?

The 5 thin coats is a good solution - I know from experience.

I sprayed the entire underside of my car and it seemed dry then went sticky. I ended up removing it all (what a PITA!) and starting again. Fortunately the Wurth dealer replaced the product for no charge.

For the fuel tank you could apply a 2 pack matte clear to get rid of the stickiness. Best solution is 5 thin coats if that works for you but the clear coat might be a solution for you.

First a very thin coat as a "primer" for the following coats. Let it dry and spray 5 or more thin coats with an hour or more drying time between them. Just build it up carefully. A color top coat can be applied after one or two days.

Otto

It would be good if they told you the painting technique required up front, or did I miss something on the can?

Once the goo is gone I'll not be playing with the Wurth product anymore, you can bet on that. The end doesn't justify the means, particularly since it's under the car!

There are other products out there that behave better and look quite good. I have used the water based Sikkens OTO, applies the same, it is a darker grey and zero issues with drying. Mine has been in for 15+ years, still good as new...

..and yes, the product is still available, applies with a schutz gun, cleans up with water.

Dennis

I had the same problem using a similar automotive rubberized undercoating product (not Wurth), on my 71. I ended up heating/scraping off all of the original coating and then painting with the new. It's also a good opportunity to apply POR15 where needed.
So I don't think it's a problem with the new Wurth product, the problem is whatever Porsche used and how it reacts with new coatings. Also consider that after 30 years of aging, road grime, fuel, etc., who knows how the original composition has changed?

Just did the entire bottom of my car with black Wurth Stoneguard and the tank with gray and no such problem. Process was to strip to bare metal then 2 coats of POR15 (applied with a foam roller) followed by 2 light coats of etch primer (sprayed) followed by 2 coats of Stoneguard (applied with Shultz gun). Dried perfectly within a few hours.

Update
 

I removed the spray-can version of Wurth Stone Guard Gray gas tank paint this morning. It took about an hour, and about a gallon and a half of gasoline, to get it off the bottom half - which is fortunately all I had painted. O'Reilly's brake parts cleaner also worked well as a solvent but is more expensive and I didn't have enough of it on hand.

But here's the bad news. NOT ONLY did the various solvents remove the obviously uncured/undried parts of the coating, they ALSO took off those sections on bare metal, masking tape, etc. that seemed to be totally dried and hard. Made no difference.

So does using a gasoline soluable coating to paint a fuel tank with seem like a good choice? Not to me it doesn't. "Originality" (and I'm not sure it is) can go away in this case.

And anyway, nothing is original once it's been reworked, even if the original materials were use. So I'm not going to worry about it anymore; here goes the off-the-shelf at O'Reilly's undercoating!

How did that work, using etching primer over the por 15? The instructions for the por15 said that won't work, once the por15 is dry...

I have a 91 964 and it looks like the stone guard grey is what was originally used in the wheel wells? Is there anywhere else to buy this besides Good speed motoring ? Pelican doesnt seem to carry it, and Good speed shipping rate is nearly 100% of the price of the product to ship it to me.

What does the etch primer do? ^

I had this problem also years ago. Never dried, I assumed it was because of the original tank coating reacting.

I applied it with a Shutz gun and while it took a day to cure, it was hard as a rock after that. It was applied over epoxy primer.