Soft soldering flux

I need to soft solder a 3" x 8" piece of gauge plate onto the face of a heavy bronze casting. I would assume that it is best to tin both surfaces first, but which flux would be better suited, a past flux such as FLUXITE, or acid flux as BAKERS FLUID.

Are there better alternatives. Would a lead based or lead free be better.

I don't want to use epoxy type glues and want a metal to metal contact.

Your ideas would be appreciated.

Bob

Hi Bob, Either of the fluxes will be OK but the Bakers fluid is not recommended for non ferrous metal so I would go for the resin flux [Fluxite] you could also use the type of flux available for plumbing, these are very mildly acidic but clean non ferrous material extremely well. Make sure you wash well with water when finished.

The solder -- use tin, same as available from plumbers merchants, tin flows to a very thin layer and is stronger than lead / tin alloys. We use this for fixing ribs on shotgun barrels and fitting new tubes into the breech, used with a resin flux and it is of course subjected to stress when the gun is fired. Tin both your components and strap together with wire then heat with a gas torch and feed in some extra solder when you see the tinning go "wet".

John.

PS Bakers fluid = killed sprites = hydrochloric acid + zinc.

Tinning is the right way to go. I would use Bakers fluid to ensure a reliable adhesion to both parts .Wash the job in water afterwards and apply a little oil to minimise chance of rusting . Colin

I would use Bakers fluid on the steel, tin it and then wash. Use resin paste on the bronze and then as John above.

The tin solder is the 'lead free' sold in places like wickes/B&Q not the same as the sort sold as lead free electronic solder. If you look at the composition it is about 99% tin and 1% copper.

Neil

Thanks all for some good advice.

Bob

PS Bakers fluid = killed sprites = hydrochloric acid + zinc.

Some years ago I saw a formula for a home-made tapping fluid known as 'Angels Tears'. Were these in response to the fate of JohnF's elves?

killed sprites?? It will be dead gremlins next!