[K3PZN-List] Soldering to Aluminum

[Philip Karras]

In general, as Kyle has discovered, this is impossible to do. This is because within far too short a time for most of us to measure, without some pretty expensive scientific equipment, pure aluminum once exposed to air becomes aluminum-oxide (Al2O3) and Al2O3 is impossible to solder to. This means that it is NOT impossible to solder to pure aluminum and I have done it. It is, on the other hand, very difficult & time consuming to do, at least the first few times you try to do it. The best way I've found to do it is to melt a pool of solder on top of the aluminum to be soldered to and then with a knife scratch the aluminum surface below the solder pool and hope you've done enough damage to get the solder to the pure aluminum surface and not too much damage to ruin the piece you want to solder to.
Note: The Al2O3 surface is very thin and can be scratched away fairy easily but it takes a bit of practice to accomplish this with just the right amount of scratching, not too little, not too much.
Note 2: Except for having discovered this while a teenager taking Chemistry, I have never found a real need to actually solder to aluminum. If you want to use Aluminum for your antenna, and it is used for most manufactured TV and Ham Radio antennas. No one solders to them, they simply drill and tap to connect the wires to the sections needing connections. Clamps or more screws will hold pieces together and screws will hold wires to the pieces as needed.
Note 3: Al2O3 does not get deeper, thicker, as time goes by. The first layer protects all aluminum below it.
Note 4: Al2O3  is also conductive as you no doubt have discovered. 73 de KE3FL,
PhilBS, MA Physics
AEC Carroll County OES, ORS, & VE
http://cs.yrex.com/ke3fl
Karras' Corner: http://cs.yrex.com/ke3fl/KarrasCorner.htm