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Mon Aug 01, 2011 10:27 am

Hi All,
Just about to start tackling some rusty seam problems, but I'm not sure if the seam sealer needs to be applied before or after the primer? obviously the rust will be removed first, by wire wheel in a grinder and/or grit blasting with a spot blasting gun, any advice would be great, thanks.

Mon Aug 01, 2011 11:35 am

The body shop that's working on my van right now is priming it first before the seam sealer. Then priming it again over the sealer.

Mon Aug 01, 2011 11:52 am

Which primer and which seam sealer is the question I think... I would start with whichever product you think will stick best. I used the 3M 8310 sealer which is super-adhesive and designed for bare metal and for use over old-seams. Then I primed on top of that.

-Bill

Mon Aug 01, 2011 12:17 pm

With some kind of metal etch primer I guess you could primer under the seam sealer. Otherwise I would wonder how strong the bond will be.

On mine I put the seam sealer over bare metal.

Mon Aug 01, 2011 8:18 pm

What do the directions on the seam sealer say?

Mon Aug 01, 2011 10:12 pm

The directions on 3-M 8115 sez--
"Apply over Clean Metal"

Bad news.
The body shop who's laying it over primer is doing the job incorrectly.

Laying a bead over phosporic acid wash, metal prep only is OK.
Never over the top of primer, it'll pull off.

Mon Aug 01, 2011 10:14 pm

I'm sorry.

I use Body panel adhesive for seam sealer.

Better for the long haul.

The clay based seam sealer I guess would be better off over some sort of primer first--Zinc chromate would be my choice for pre sealer prime.

Tue Aug 02, 2011 1:07 am

Some vans are starting to appear in Europe with fresh expensive restorations where the body seam sealer is applied after the final paint top coat. Just like you get on current commercials like VW Crafters/Merc Sprinters etc.
Experience has shown that paint over flexible seam compond just leads to cracking and then the inevitable water ingress. The T3 isn't the stiffest bodyshell around, especially when coupled with firm dampers and hard sprngs like H&R's.
All the extra black lines do look a bit weird at first though...

Tue Aug 02, 2011 7:10 am

I have tried over and under seam sealing.
The factor that determins longivity has been whether the seams have been rust encapsulated or not first.
If they have and the seam sealed and than primed...the rust has been kept at bay.

The opening of the seams and removing all of the old sealer is critical :!:

I also have tested many different layerings of products to seal and protect the inner cavities and underbody.
At my shop I will only consider completely striped, bare metal resprays with underbody protection.
All other localized bodywork has failed within 5 years.
Not worth the expense IMHO.
Do it all and do it right.

Tue Aug 02, 2011 7:53 am

Bare metal, rust removed by sand blast and nothing else:

1-Dupont Chroma Premier Etch Primer 22880S and 22806S reducer
2-Zink Spay can is fine but highest quality (DON'T SAND!!!)
3-Primer (Epoxy for best result) Proform PF 656C (SAND!)
4-Pain-table seam sealer, pale or dark color depending on the van color.

On the first base coat you do the seam first and at the end of first coat you do the seam again.

Ben

Tue Aug 02, 2011 9:30 am

Many thanks for the replies, Haven't got the sealer yet, think I'll try to get hold of some of the 3M Seam sealer mentioned.
a previous repair where a panel section was welded in, which a local body shop did, had sealer applied after primer, but it was showing signs of rust again below the sealer after a year or so, then again, that isn't to say the rust was removed well/encapsulated, or the primer was applied to clean enough metal.

Fri Oct 26, 2012 6:17 pm

ftp2leta wrote:

Bare metal, rust removed by sand blast and nothing else:

1-Dupont Chroma Premier Etch Primer 22880S and 22806S reducer
2-Zink Spay can is fine but highest quality (DON'T SAND!!!)
3-Primer (Epoxy for best result) Proform PF 656C (SAND!)
4-Pain-table seam sealer, pale or dark color depending on the van color.

On the first base coat you do the seam first and at the end of first coat you do the seam again.

Ben

Given Ben's suggestion to use an epoxy primer.....

So I've got 2 coats of etching primer on bare metal seam. Inside of seam was treated with rust converter.
.....

Edit: sorry. Posted that (rhetorical) question in another thread. Thought this thread was in the Vanagon/EV forum.

Neil.

Fri Nov 09, 2012 10:52 pm

It's been a while since I restored my old 69. I no longer own it but I used this:

I wire brushed all the rust and then wire brushed all the old sealer off. I painted it with MasterSeries and then brushed on the seam sealer.

It was then primered and then painted. I was real happy with the results.