..like crevices, conventional plumbing flux and when I've had luck with most solders, four% silver bearing solder is much better In the long term...kinda high priced tho... I'd Harris solder on hand at some time so no big deal for me but high-priced if you do not need the strength https://whentoremovecollisioncove99617.fare-blog.com/27389190/the-5-second-trick-for-types-of-solder-to-use-on-aluminum-radiator