'68 rust repair question on coatings

[pfrancescutti]

Hello all

I'm 100% new to this type of work but I taught myself how to work with sheet metal and how to weld over the past couple weeks while trying to get my '68 ready for the road. I bought her about a month ago to be my daily driver while I install a new power plant in my '92 GTI.

She runs like a clock and has a solid pan with no structural rust issues. Where she did end up being a bit worse for wear was in the passenger-side rocker panel and in the inner fender areas near the battery and opposite side. Someone had previously "repaired" her with a tube of silicone :/. I've fabricated a bunch of new sections for her and this is what I've got so far, all that remains is the passenger side inner fender area.

Inner fender area:

Rocker panel:

My question is, now that I have a mixture of old rusty steel and new shiny steel, what do I use to coat this on the underside? I'm thinking POR15, seam-sealer then undercoat but is POR15 the right product to use on the new steel?

Epoxy primer on new steel, POR15 on old then seam-seal and undercoat?
Epoxy or POR15 on everything?

I'm lost on this.

Cheers
Paul

[wcfvw69]

Nice work on the repairs you've done so far. Personally, I wouldn't use POR15 on your bare metal repairs. You'd be better off using a etching primer over the clean, bare steel and then hit it with a good quality primer, then paint.

If you took your pictures to your local autobody paint supply house, they could offer some good suggestions or products as well. You also might consider looking into cavity protector sprays for inside your heater channels another areas. If you don't treat inside the welded sheet metal, you'll have to do this again very quickly as it will rust inside out.
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[panicman]

Grab a couple more of those Winter Ales and read this sticky:
http://www.thesamba.com/vw/forum/viewtopic.php?t=131753
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[beetlenut]

Whatever you use, take some 100 grit sandpaper and rough up all that shiny steel, to give whatever coatings you use some bite to grab on to. I used all Master Series products on mine and was very happy with the results.
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[pfrancescutti]

[pfrancescutti]

Thanks for the input guys, looks like I'll have to do some more research.

I got some more metalwork done this evening. Passenger side inner fender. I'm getting better at planishing. One piece of steel this time instead of four.

Cheers
Paul

[Mike Fisher]

Brush on Master Series silver & black on the insides/chassis w/no sanding required, but spray sealer/primer on the exterior painted panels.
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[c21darrel]

At minimum, if I dont sand, I always etch the fresh metal with phosphoric acid then Masterseries.
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[raygreenwood]

Some note on that original testing thread.....some of the original failures were caused by the tester who posted....not understanding the use or chemistry of the products he was testing.

Some of those products are like apples to oranges. By far the most effective rust "converter" out there is the Jasco.

It doesn't matter whose opinion or testing...thats fact simply because the Jasco has the highest solution strength of any of the phosphoric acid based rust converter products on the market.
To equal Ospho.....the Jasco needs to bee diluted with distilled water 3.5X. So one quart of Jasco mixed with 3.5 quarts of water will make over a gallon of solution that is comparable to Ospho.

Of course it burns you and eats concrete...its Phosphoric ACID

the reason the Jasco failed is because it was used incorrectly. If you use it full strength....which I do....it will give the best combination of rust conversion and rust dissolving. it works very similar to muriatic acid.

It will dissolve all rust that is under about .003" thick on one application, leaving bare metal. It will convert all rust up to about .010" thick into black iron phosphate.

In this manner....it can replace the serious derusting step of acid washing with muriatic acid and the subsequent need to heavily neutralize later and then use a phosphoric acid to reconvert flash rust.

The problems encountered with products like Jasco and Ospho are that you MUST allow them 24 hours to dry naturally or used forced hot air to dry them. You must NOT rinse them with water until they are fully dryed.

The next problem is that on high solution strength products like Jasco, there are other oxides that appear as dust/crust or a film on the surface. It is these that inhibit paint grip.

As the products instructions note.....after full ddrying, dont let these products lay around and absorb humidity and moisture to reactivate the crusty oxide that is acid on the surface. Solvent wash them with a clean, fast drying mineral spirit and then paint them quickly with a primer.

Chances are high that it will be eons before these parts rust again. Iron phosphate once sealed is a serious rust inhibitor on the level with Zinc Phosphate. Ray