..such as crevices, standard plumbing flux and though I've experienced luck with most solders, 4% silver bearing solder is stronger In the end...kinda costly tho... I had Harris solder available at the time so no big deal for me but expensive if you don't need to have the toughness for https://types-of-trailer-hitch-co11110.dsiblogger.com/60034536/a-simple-key-for-types-of-solder-to-use-on-aluminum-radiator-unveiled