For that application I would strongly recommend using this flux with the Harris Stay-Brite-8 solder:
Stay-Clean Aluminum Flux
It works very well for soldering Stainless Steel AND Aluminum.
Do a Google on "Harris Stay-Clean Aluminum" to get a listing of a lot of places to get it.
Stay-Clean Aluminum Flux
It works very well for soldering Stainless Steel AND Aluminum.
Do a Google on "Harris Stay-Clean Aluminum" to get a listing of a lot of places to get it.