How to Solder Copper to Mild Steel
- 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.
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