Soldering aluminium sheet metal. Which flux?

I am busy on a car with MIG welded sheet metal from 1050 grade aluminium. My welder advised me to get 35/65 S7 ally welding sticks (tin/lead, 1/4" thick) to fill gaps and followed with the procedure: Wire brush surface. Pre-Heat wider surface area to 170F. Then beyond 500F on the spot while filling with S7 stick.

I figure a flux is needed. I can’t reach my other welder to tell me. Perhaps somebody here knows. I hear about zinc chloride flux and many others…

Suppose the flux has to contain tin and lead as the welding sticks?

Can’t help with the flux but you need to use a new stainless steel wire brush otherwise the ally can be come contaminated.

Thanks, every little bit helps. I went to get Dowty washer at Hansa Flex and next door happens to be a welding/soldering specialist whom I ignored for years. He had some additional info! I report back.

I would also type your exact question into Google and Youtube

There is a remarkable amount of videos on so many specialised tasks these days

(in fact I just did that for you and there is lots of info)

One must be selective, but even reading comments on the Youtube vids can be very illuminating

Yes, I shall do that more. Your point exactly: Must be selective. The metal compositions, flux and welding stick seem to be critical. As is temperature and clean surface.

Today’s priority was mechanics and cooling system. Also a manual choke. Different topics…

Not sure about your good friend, but the alloy certainly will… :slight_smile:

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