Spot Weld Paste

I read that one time, and didn't think twice about the end result desired. So many things have changed since the engineering of that weld and paste scenario. I have a good idea that might work instead, but no idea on where to find that paste mentioned.

I used to make roof and chimney flashings for a living, along with a bunch of other things , all at the same time, and we (me and the rest of the metal shop guys ) used a process called soldering. This was done after the spot welding procedure and sealed the seams watertight and sealed them with the (mostly lead) solder. If the paste is not available, you might try and find a large soldering iron and utilize this process too.

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Though I don't know how it was done back then, I can tell you how I did it when installing my new pans. Go to a welding supply shop and get some weld-thru primer. It's not cheap, I think I paid ~$16 for an aerosol can. Hit both of the overlapping edges with it, weld, and then use a good seam sealer from both sides. That should do it...

-Chip

Wes Pears> The VW Manual (Big Blue One) talks about a spot weld paste that you put

I do this regularly.. that's how "lead sleds" were made back in the day.

Lazy people use plastic filler, it's faster, easier and more easily available.

The priming compound / paste for soldering ("leading") weld seams and other car body metals has lead and tin and acid in it so it will etch itself into the metal. Bare solder won't stick to sheet metal or weld seams without it. (Don't even try). You can only apply it to SHINY clean metal. It won't stick to rusty, dirty or darkened metal (typically around fresh welds). So you first need to polish the area you wish to cover. I have managed to make it stick to sandblasted surface too. It's a bit more difficult. Sometimes you can apply a thicker layer, and if you are careful and patient, you can stretch the solder over a non-sticking area. It will leave a pocket underneath of course.

When you're done spreading the priming compound, you let it sit for a while and then start heating it with a small gas torch. Once it changes color (it will turn silvery yellow), it's hot enough for you to WIPE IT OFF. you wipe off all the excess lead/tin that the compound had in it, plus all the impurities that sort of float to surface. What is left behind is a mirror shiny surface of lead/tin to which you melt more material on from a solid lead bar. You do NOT use a resin filled soldering tin. (The impurities iun it would ruin the job).

The tricky part is controlling the heat, you have to keep heating the work area constantly until you have managed to apply a smooth layer of lead on there. Use a non-metallic spatula or something, dipped in vegetable oil. (wipe off the oil but leave the tool sort of glimmering wet of it). This way the solder won't stick to your spreading tool.

When you're done, you will have a very rough surface that's hopefully solid inside. You can start shaping it with a special lead file, but I have found that a regular sanding disc on an angle grinder works best. Shit will fly, so protect your eyes. Don't spend too much time sanding in one spot, the heat of the friction will soon start melting the lead. Move fast, use light pressure only.

When you are pleased with the result, you can wash the area with some good solvent that doesn't leave any film. (has to be washed down for paint etc. to stick).

if you can't get a smooth finish, you can aim for a rougher finish and a shallow indentation, and finish the job with a thin coat of plastic filler. Note that sandpaper eats lead and plastic filler differently.

Jan

I left this step out I suppose because it's been so long since I have done it. ............We used slightly diluted Muratic Acid to etch the surfaces before soldering. Sorry for the missed info.

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