We Value Your Privacy

We and our partners use technology such as cookies on our site to personalise content and ads, provide social media features, and analyse our traffic. Click below to consent to the use of this technology across the web. You can change your mind and change your consent choices at anytime by returning to this site.

Update Consent
Loading ...

How to Solder Copper to Mild Steel

Updated April 17, 2017

The most common situation where you would need to solder copper to mild steel is in the home. Copper and steel are used to make pipes for plumbing systems, and the two types of pipes are connected by a dielectric union. This is a joint union that is threaded in the middle, with one side copper and the other steel, and a rubber gasket in between. The copper side of the union is soldered into place on the steel pipe. Soldering this union is done the same way you would solder copper to mild steel in any situation.

Loading ...
  1. Clean debris off your copper and metal with a wire brush. If you are soldering a dielectric union, unthread the union connection and wrap Teflon tape around the thread. Screw the steel part of the union onto the pipe by hand, then tighten it with a wrench.

  2. Sand the area of the copper you will be soldering with an emery cloth. Apply soldering paste, or flux, to the sanded area. Join the copper to the steel as the two metal pieces or pipes will be connected.

  3. Unroll 6 to 10 inches of solder. If you are soldering a dielectric union, bend the last few inches to a 90-degree angle. Heat the areas you will solder with a propane torch. Wait for the flux to sizzle. Touch the seam with the tip of the solder. When it melts, apply 1 inch of solder to the area or around the seam. Wipe off any extra solder with a rag and wait for the metal to cool.

Loading ...

Things You'll Need

  • Wire brush
  • Teflon tape
  • Pipe wrench
  • Emery cloth
  • Soldering paste
  • Propane torch
  • Roll of solder
  • Rag
  • Dielectric union (if applicable)

About the Author

Loading ...