How to Solder Stainless to Copper

Stainless steel and copper sometimes need to be soldered together for beer brewing equipment.

Silver soldering, or brazing, is the best method for joining stainless steel and copper.Silver soldering, or brazing, is the best method for joining stainless steel and copper.
Soft soldering, which is used for electronic equipment, is not a strong enough bond for the fitting together of stainless steel and copper. Instead, a silver soldering technique called brazing is required. Brazing requires a great amount of heat for the strongest joint possible. The best brazing alloys have a melting point between 1094 and 1598 degrees Fahrenheit. Use caution when brazing and always wear good safety equipment.

Clean the stainless steel and copper by scraping the surface of each gently with a piece of wire wool.

Place the stainless steel and copper joint together on pieces of fire brick to lift them off the surface. This prevents fire.

Mix together the borax flux powder with water to make a paste. Brush the paste along the joint. This prevents oxidization in the joint, which would create a bad connection.

Light the pilot light on your torch according to the instructions for the torch. Once lit, put on your safety gloves and welding mask. Turn the gas and air control until a flame appears at the end of the torch.

Run the heat around the entire piece of steel and copper to slowly raise the temperature of the metal.

Move the flame close to the joint so the blue portion of the flame touches the joint. Heat until the metal turns red.

Touch the brazing alloy, which comes in the form of a rod, to the joint. Run the rod along the joint to seal it, applying the to the metal to keep everything hot. Let the steel cool slowly to prevent cracking.

Things You Will Need

  • Wire wool
  • Fire bricks
  • Flux
  • Brush
  • Brazing torch (blow torch)
  • Lighter
  • Work gloves
  • Welding mask
  • Brazing alloy rod