Solder to stainless steel?

[VK5PJ]

Hi,
 many years ago a good friend shared a method that allows you to solder with normal 60/40 solder to any stainless object.  I have over the years used this to good effect but have not ever seen it done by others.. my first attempt was to a kitchen sink in a rental house, truly surprised how easy that was to do with the right technique.

here is my latest example of soldering a copper wire to a stainless bolt, yes its a good quality stainless bolt not some cheap impostor.  



in case the photo does not show here is a link: solder to stainless
If this interests others I will share the process used.

I should give credit to the person who passed this onto me many years ago, thanks Bob, VK6KRC for many of the work shop hints you have shared with many people over the years.

[ZL3RC]

Go on Peter tell us how you do this.

Can you break it off at the bond?
It looks like a good puddle of solder on the top of the bolt so Im guessing not.

Roger ZL3RC

[VK5PJ]

Hello Roger,
yes there was a decent puddle of solder and it even extends down the 2.5mm hole I drilled down the core of the bolt head some 6mm in depth to test my theory that I could get the solder to flow into the hole.  The hole was to ensure my finished connection had a good physical bond between the copper wire and the stainless bolt and not just some single point connection at the surface of the bolt. 

I know I have over played the build up, sorry, could not help myself... 

The method to get this to work is very simple, clean the stainless surface with a non metallic cleaning pad like a scotch bright dish cleaner, open the secret bottle of Rust Converter (source of the needed Phosphoric acid) from most hardware stores, brand of the product is not important just that it contains Phosphoric Acid.

Apply a liberal pool of Rust Converter to the surface so the area you wish to solder to is covered.  Pick up you soldering iron, in my case and old style Weller iron with a 7 series chisel tip and your spool of 60/40 resin core solder.

Hold the work piece in some rag to stop the heat being drawn away by the vice jaws and heat the intended joint through the puddle of Rust converter with your iron,  Ensure you do this in a well ventilated spot as I am unsure what the fumes coming off are but I am sure they are not good for you.

The rust converter will slowly boil away but not before the solder starts to take to the surface and with a little practice you can produce some nice solder joints.  I am yet to see one of these joints come apart over the 30 years I have been doing this on stainless rod, bolts and flat.

[ZL3RC]

Thanks Peter.
Ill have to give it a go.

What would be very useful, and Im sure you'd agree, is some way to solder to Aluminium.
Theres that "stuff" you have probably seen on somethingBay for welding with a heat source but I haven't tried that.

Have to do a Google search and see what I find.

Thanks again and Ill post my results :-)

Roger ZL3RC

[VK5PJ]

Will be interested to see who you go Roger, have tried to varying degrees of success to solder to Aluminium, if I remember the process it goes like this,

clean surface with non ferrous brush and coat the surface with oil to provide and air exclusion layer, clean again while the oil is in place (the hard part) to get a freshly cleaned surface and exclude the air so it does not immediately oxidize, apply heat to the aluminium via a soldering iron tip through the oil (not gas) and proceed to tin the surface of the Aluminium with standard 60/40 solder.

While I am working on my solder to stainless project on a 50 MHz yagi I am rebuilding (it has dissimilar metal contacts in the feed arrangement that is causing me grief), will see if I can revive my solder to Aluminium skills and if it works out will post a photo

[VK6RO]

In the late 70s  i had a 2 el Hf quad made from stainless steel wire.

At the local gas kleenheat??  or boral?  gas supplier i purchased a stainless steel soldering kit.. dead easy to use

we lived maybe 600 metres direct from indian ocean and on rough days some salt spray  was floating around from memory

I think the kit had flux and solder for stainless steel.

All from memory

vk6ro

e&oe