Underseal, protection etc

I'm going to strip the full underside of my car to bare metal, and asking preferences on what to use to cure the underside

Upto now I've read epoxy mastic, as it can be put direct on bare metal and can be painted over! 

Or, my mate who's a painter by trade says to etch prime, 2k prime, seam seal the seams, stonechip and paint then. 

Any ideas or recommendations please  

id be interested in this too, the epoxy mastic ive also looked into but im not sure as to what exactly to use, i too will be going back to bare metal!

I'll explain what I'm doing at present and why and let you decide which way to go as it is a bit mind numbing at times and also varies from person to person. Both Bilt Hamber and Rustbusters websites are very good sources of information and products. Obviously you are removing the old  first to see what's left. If it's rotten ie holes you need to cut out and weld in new metal, if it's rusty you need to be brutal and attack it to see if holes appear. It doesn't matter what the  manufacturer's says about it's magic potion of rust converters the best course is to get rid first. So attack it with grinders, wire brushes in drills, scrapers and shot blasters if you have them. You may aswell find holes at this stage than 6 months after when your new paintjob starts bubbling or at MOT time when they are poking about underneath.Once everything is as prepped as possible ie linished sanded or blasted I have then used a rust converter to treat any areas that still show rust staining or heavy pitting or to brush into exposed seams that cannot be cleaned out in any other way. Once dry I have then painted everything with epoxy mastic to give everything a solid base. All seams have then been sealed with seam sealer. Brush it out with a trimmed down brush to try and replicate the factory effect. Try to fill voids and smooth out joint areas to avoid the crud getting stuck at a later date. The whole floor area has then been sprayed with stone chip protection, this is rubberised so in theory stones etc should bounce off. If you're going for concourse you would normally then go for paint finish over the top. I want  a practical finish that will give maximum protection and maximum life to my car so I am painting on 2 coats of Dynax UB followed by a sprayed coat to ensure it gets is in all the nooks and crannies. This product is similar to what VW used on the floorpans and is very good at resisting abrasions. All the cavities will be injected with a cavity wax.. The UB finish is black so should look neat where exposed under the arches compared to the paintwork. My only other advice to anyone is think of future maintenance as well, every year or two  get underneath, get under the arch liners, clear out any muck ,dry it out and give is another coat of the sprayed wax finish of your choice. All finishes get abraded and start to dry out so a fresh coat rejuvinates the protection .I hope my advice helps you but remember it is all in the preparation. Andy.

I did this last year and used epoxy mastic 121 on the shot blasted surface. I was impressed with the results. It seems quite sticky when it goes on but goes rock hard.
Once epoxied I stone chipped it then used Dinitrol as a final wax.(Similar to OEM) and cavity waxed in the nooks and cranies.

Check out my thread here: http://vwgolfmk1.org.uk/forum/index.php?page=topicview&type=misc&id=your-mk1-golfs_2%2F-quot-black-bullet-quot_2&start=40

Wow! Thanks Andy! Think il be going down the epoxy mastic route if I'm honest. Then stonechip and maybe paint, il see about that. 

Much appreciated and also more advice could also help..

I'll second what brad said,mine will be getting this treatment as soon as the weather warms up,great bit of advice there mate 

Great advice here, I was wondering about this and now 5 minutes later I've got a plan!

My link wasn't working to the Dinatrol wax I used. Fixed now….

http://www.dinitrol.co.uk/Portals/0/docs/DINITROL%204941%20TDS.pdf

or

http://www.dinitrol.co.uk/home.aspx

and

http://www.rust.co.uk/products/category/28117/epoxy-mastic-rust-proofing-chassis-paint/

Thanks yomp! I'm also
Looking into 3m bag sealer if anybody has any reviews on this or advice on it. Gives an oem finish! 

http://vwgolfmk1.org.uk/forum/index.php?page=topicview&type=misc&id=your-mk1-golfs_2%2Fswallowtail-1975-the&start=120

I used the 3m stuff, here a link to my project. I find using stone chip on hte underside is no good, as in time it starts to fake. 3m is rubber in a bag, best thing i have come by…..i hope my process helps people too.

I know it's an old thread but looking at the 3M stuff myself… Would you mind letting me know how many bags you used, and where you got them from? I cant seem to find a supplier and have no idea how much they are?

Cheers

Also any reason you went for the por 15 over the epoxy mastic? Cheers

out of interest why are people stripping off the underseal just to re do it again? if you have no rust coming through on the inside and underneath isn't scuffed in areas surely its just a waste of time?

I was asking the same thing.. had no intention of striping it and lost a lot of sleep over it… I did toy with the idea of leaving it well alone, I really was stressing about why the hell do I need to remove it if it looks good, no rust on the inside of the car etc..

Started lke this.. Looking pretty reasonable to be honest bar a few obvious bits-

..

Mid way through it looks like this, think i've been vindicated and well worth the effort.. If i'm gonna spend nearly 4K on the top, seems silly to risk leaving the underside without even a little investigation..  I know it's a pretty solid floor and most of it is just surface rust.. but who knows what that would be like If left for 2-5 + more years..