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?
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.