How to Solder Aluminum Thin Wall Tubing

Richard Asmus

The difficulty of removing the oxides makes soldering aluminum difficult. Aluminum conduit, made from 6xxx series aluminum with a magnesium alloy, poses a more difficult problem. According to a 2010 article by A. E. Gickler in the American Welding Society's online magazine, "the 6xxx (silicon and magnesium added) series may or may not be solderable depending upon the individual alloy." And since aluminum thin wall tubing (EMT) isn't designed to be soldered, you have to experiment to see if you can solder your particular alloy.

You may or may not be able to solder aluminum thin wall.
  1. Clean off any dirt, paint, oil or grease from the conduit with solvent and a rag.

  2. Apply flux to the areas to be soldered. Place the surfaces so that they are touching, since solder will not fill gaps.

  3. Thoroughly heat the area with your torch.

  4. Touch your solder to the aluminum joint. If the solder melts instantly, the joint is hot enough. If not, continue heating. Do not melt the solder with the torch. The hot aluminum has to melt the solder directly.

  5. Watch the solder as it melts. If your flux and solder suit your particular alloy, the solder should flow onto the aluminum and seep into the joint. If it just rolls off, experiment with different fluxes and solders. There is no guarantee you will find a solder that works.