..including crevices, normal plumbing flux and although I've experienced luck with most solders, four% silver bearing solder is more robust Over time...kinda highly-priced tho... I had Harris solder available at the time so no major deal for me but high priced if you don't want the strength for off road/ https://myleskykft.izrablog.com/27789626/a-secret-weapon-for-types-of-solder-to-use-on-aluminum-radiator