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Sat Jun 05, 2021 5:41 pm

I did some google-fu on soldering sheet metal, as I recently cut out my floorpans and welded in some new pieces. To fill the seams and (from my lack of skill) inevitable gaps, I would like to use solder applied with a propane torch. Most forums I browsed indicated that brazing is stronger, but requires the much higher temperatures of acetylene. MAPP is no longer made, and MAP-Pro is barely any hotter than propane, and therefore not worth the extra cost.

I would like to NOT use seam filler, because if I end up having to repair anything (busts a weld, or rusts through again, what with the salt water here) I won't have to scrape the stuff off and still have it clog up my wire wheels.

I couldn't get specific answers about what supplies I needed, so I raided Home Depot and and want to know what I should keep. I have also within the last half hour heard of Eastwood soldering materials (courtesy of this thread https://www.thesamba.com/vw/forum/archive/index.php/o-t--t-422444--.html), which also include a wide array of products - solder sticks, solder paste, flux-n-solder, tinning butter, etc.

Will any of these that I have work?

Also, will they (or the proper solder, if not these) help fill cheese holes? There were a few sections that would have been difficult to cut/weld, so I left in. I am limited on time, skills, space, and budget, so I hope mostly for these repairs to get me by for the next four years until I move back home and have proper resources.[/url]

Sat Jun 05, 2021 8:08 pm

I wouldn’t use that at all. There are some things you can use but I wouldn’t use that. You can use master series and keep covering it until the pin holes are gone. In some very small areas I’ve used JB weld stick and then covered with master series. You may also be able to use a few coats of epoxy primer.

Sat Jun 05, 2021 10:17 pm

I brazed up a few pin holes when I was a kid. Dad had one of those cheaply, screw on bottle, type solder torch. Worked great!

Sun Jun 06, 2021 6:42 am

Post photos of what you want to try and close up with solder. I am interested in both the location, and the width of the gap you are trying to bridge.

Sun Jun 06, 2021 8:12 am

The solder you are posting is acid core and it won't work. Well, it will work if you don't mind it bleeding through your paint and continuing to rust underneath. The other products are likely acid which doesn't contain the lead you need to tin the surface.

You are going to need lead sticks and a lead flux in order to do what you intend. The process is to tin the clean, rust-free surface. Wash off all the flux-acid with a blend of very hot water and a neutralizer (baking soda), then apply body solder (lead) to the area with a paddle lubricated in tallow. Wash again, wipe it down with acetone to remove any tallow which floated to the surface, then body file.

Can you use the products you have? I met a guy once who was very impressed with himself at the fact that he 'welded' aluminum to steel...

Sun Jun 06, 2021 12:18 pm

seam sealer.

Mon Jun 07, 2021 11:18 am

I still get pin holes no matter how carefully I weld. If they bother you, shine a light behind your welds to find them, then mark them with a sharpie, weld them up and grind them flat. It’s tedious but probably easier than messing with body solder. Coat with master series, seam seal if you like and top coat. You can back up your welding with copper if you are worried about burning through.

Mon Jun 07, 2021 4:37 pm

^^^^ This.

Just keep practising with the welding. I think everyone has these pin holes when they first start. I did.

Just do the light trick and zap each one of those pinholes for a second. Repeat until there are none left. It will be quicker and probably cheaper than looking for alternatives and your welding will get better from more practice.