[time-nuts] cesium clocks..

Neville Michie namichie at gmail.com
Sat Jun 28 06:57:51 EDT 2008

On 28/06/2008, at 1:14 PM, Bruce Griffiths wrote:
> Stainless is trickier to solder than constantan.
> Welding may be preferable.
A hint for soft soldering stainless steel, iron, nickel, chromium,  
copper, brass, nichrome etc. but not aluminium.

Apply a very small amount of phosphoric acid to the clean metal when  
COLD, then solder with a soldering iron and pure solder.
The metal will then solder as easily as clean copper.
The flux residue is very water soluble and washes off.
The dilute acid is not a problem but the hot concentrated flux  
residue (mainly phosphorous pentoxide) is corrosive to fingers and  
clothing and should be treated with respect until dissolved in water.
If you apply the phosphoric acid and heat the metal for a minute or  
so before soldering then some metals ( mainly ferrous) will develop a  
phosphate coating as in the Parkerizing process and you will never  
solder it. You will need to clean the metal
with abrasive paper until bright.

Quite often I "tin" the item with the phosphoric acid as a flux, then  
wash it clean, then later it can
be soldered with resin cored solder with other components. The  
phosphoric acid and resin will
not act together as a flux but make a mess.
Not recommended for children.
Just in case you were interested,
Neville Michie

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