I would etch prime the metal first, then seam seal with polyurethane. I would then, re prime and then top coat. What products you use is up to you. I have used tigar seal in the past but many others are available.

 

have you tried asking rustbuster?

i don't think i'd bother doing 121 over the sealer. the 121's job is to stick to the bare steel and be waterproof, the sealer's job is to flexibly seal any joints in the panels. between the 2 you end up with a waterproof coating. i'd just stick normal primer/stonechip/whatever straight over it.

 

Always best to paint any overlapping joints (preferably with a thinned paint) where you would use seam sealer as it will penetrate the joint where a sealant would not. Have not used etch primer in 41 years and never would... Nasty, porous, moisture-permeable stuff. Yuck.

Cheers, Carl.

 

Yea, thin the 121 down with the supplied thinners and use a small brush to really force the paint into the seam. Do 2 coats.

I did this for an inch or so either side of the seam and once dried I seam sealed and then painted over everything with 2 coats.

This I did to be a tart and make the floorpan look nice but so long as you thin the paint to get it into the seams then you can seam seal over the top and leave like that. IMO the seam sealer helps stop crap collecting in the seam joins and this along with time and moisture in the air is what will make a paint product fail over time.

 

once dried I seam sealed and then painted over everything with 2 coats.

Ahh, I assume this was this the approach you took on your awesome oval resto Just out of interest; did you spray, roller or brush the mastic 121 onto your chassis? The results were stunning!

Firstly, I would say, avoid having overlapping seams if possible on your repairs. Butt weld if you can.

Thanks Dave. All of my pan repairs have indeed been butt welded with great care and ground back to an invisible finish (I'm a slow working perfectionist!) The seam sealing I am referring to is just on the stock factory joints that would have been sealed up originally (i.e - topside of framehead, naps hat, floor pans etc).

The branded ones like Tiger Seal and Sikaflex are far superior to cheap generic types, but considerably more expensive.

Nice one, I stick to these recommendations!

 

You are all brilliant and I massively appreciate your guidance!

Carl/Psimitar- I should have mentioned that I am intending on spraying the mastic to get the best finish and reach all those areas where a gloss roller or brush would struggle. Would spraying (thinned 20% as recommended) be sufficient to seal up the seams, or should I really get in there with a brush beforehand?

keekster - thanks for the recommendation of the Tiger seal I notice that they produce a black version which could look good on top of the 121

Thanks again all!

 

A sprayed coating will never penetrate as well as a brushed application. Spray mists do not generally go around corners and enter seams!

Cheers, Carl.

 

Spray mists do not generally go around corners and enter seams!

Haha, yeah, I think I knew that deep down - was just ignorantly hoping it might be otherwise so I would have less to worry about. Thanks Carl!

 

Personally I avoid seam sealer at all costs seeing what goes on underneath it after a few years, it should be called rust incubator not seam sealer. Even peeling off VW's original seam sealer leaves a line of rust with good paint on either side. I hate the stuff.

Firstly, I would say, avoid having overlapping seams if possible on your repairs. Butt weld if you can.

Secondly, brush coat a good, thin paint that will wick itself into any gaps and spaces between the welding. POR15 wicks in well and self flats afterwards, although prep must be perfect. Epoxy mastic seems to be much more forgiving but not sure how well it wicks itself into the cracks. Only just started using it.

Look at it this way - if the seams between your panels have gaps so wide that you need seam sealer to cover them over, then your panel fit and welding is what needs sorting out.

Just my 2p -

Dave.

 

Personally I avoid seam sealer at all costs seeing what goes on underneath it after a few years, it should be called rust incubator not seam sealer.

The factory stuff and the cellulose junk in a tin, yes. I think 1k polyurethane mastic is another league though, and is the only product to consider if deemed absolutely essential. The branded ones like Tiger Seal and Sikaflex are far superior to cheap generic types, but considerably more expensive.

Yes, lap welds are the joints of the Devil, however unavoidable on some of the longest repair seams - floor pans for example. Other repairs, though? Butt welds only as Dave advises.

Cheers, Carl.

 

20% works pretty well for thinning and allowing the 121 to seep into seams but going a bit more just increases the drying time.

However, for the spray gun you need at least a 2mm nozzle. 2.2mm might be better. I only had a 1.8mm and had to thin it by a good 30% for it to flow out of the gun properly.

 

Thanks Yeah, I just checked the nozzle size on my gun and its 1.4mm

I guess I could take a punt on a 2.2mm cheapo like this, which should do the job: https://www.amazon.co.uk/Sealey-SSG501-Spray-Gravity-Set-Up/dp/B000ROB7Q0

So, did you paint the inaccessible areas of the chassis (i.e - around the seat frames) with a brush before spraying the coats on then?

Sorry for these fussy noob questions, but I have spent so long bare metalling the bloody thing that I would be crushed if I fudged the paint now. On the other hand, I could just go down the foam gloss roller route and keep things simple :crazy:

 

Wow, so cheap compared to things over here

anyway, yea it should work fine. Even if only for the job at hand. cleaning with gunwash is the way to keep it usable.

Make sure the bare metal has been keyed with 240 or 180 grits sandpaper for best adhesion. Use a quality degreaser/panel wipe to clean everything before you paint.

I used a brush on all areas the roller or spraying couldn't reach and defo do at least 2 coats when spraying as it lays down thinner than if brushed or rolled on. I even used the thinned paint for the seat runners to make sure it got under and into the lap join that exists there.

 

My sincere thanks dude! Really great advice. I shall be laying the paint down as soon as I have finished cleaning & prepping all the nooks & crannies. Man, bare metalling the pan is a gruelling never ending mission