What flux for soldering old brass?

[Pbassred]

I have a big old MOSFET amp with T-03 devices screwed into brass bushes which in turn ar soldered onto the PCB. After a 1/4 century of rock and roll the solder arround the bushes is cracking, so I'm cleaning and resoldering.

What is the best flux for that?

 

[fizzard]

Plumber's flux works pretty well on brass, but I've always read that it doesn't mix with electronics. I've never tried it myself. The zinc in brass oxidizes quite quickly, so a more potent flux is required for soldering.

 

[Mitch Alsup]

I have always had good luck with the wattery flux that comes with silver solder when tin-lead soldering brass to steel or copper.

 

[unclejed613]

an aspirin tablet (NOT ibuprophen or acetaminophen, or containing caffeine) works as a good flux for brass or even steel (not stainless steel). since it is a mild organic acid (salicylic acid) it must be cleaned off with hot water. also, the fumes are very irritating but dissipate quickly, so use with adequate ventilation and keep the flux smoke away from your eyes and nose (a small computer fan will do fine).

 

[AndrewT]

an aspirin tablet .... works as a good flux for brass or even steel (not stainless steel). since it is a mild organic acid (salicylic acid) it must be cleaned off with hot water.

dissolved to make a saturated solution or applied as a powder and melted with the heat?

 

[Juergen Knoop]

I'm very fond of oldfashioned colophony based flux.
It is claims to be non corosive and does not smell to bad.
http://www.loethonig.de/
Regards