What Solder to Use on A/C

Lead-Free Solder

• Lead-free solder is an alloy mixture usually containing several metals including tin, copper, bismuth and silver. It is safe for all copper pipes including potable water lines because it does not contain any lead products. You need to use an external flux with this solder for optimum adhesion.

Lead Solder

• You can use lead-based solder on air condition lines due to them not containing drinking water or coming into contact with any potable water. Leaded-core, acid-core and rosin-core solder contain a mixture of tin and lead. Standard solid lead solder requires the use of an external flux, but acid core and rosin core do not. The acid core and rosin core have flux within the solder itself, which cleans the piping when the solder contacts the surface.

Flux

• It is essential you apply flux paste to the area you are soldering when using certain types of flux. The flux etches the surface, which removes all oxidation. This allows the solder to properly bond with the copper pipe. The flux also helps the solder flow into the void area, filling it completely. Brush the flux onto the surface thoroughly, especially into the joints of a connection.

Preparation

• It is essential to remove all contents of the air conditioning line before attempting to solder because the contents can have an adverse effect on the solder. To properly solder copper air conditioning lines you must first sand the tubing with an emery cloth or sandpaper to clean any foreign substances from the surface. This allows the solder to properly bond to the copper surface, creating an air-tight soldered joint.

Soldering

• Heat the pieces of copper tubing to be soldered with a hand-held torch. Apply the heat evenly to the piping until it is hot enough to melt the solder. You should protect all areas around the soldering point to prevent fire or heat damage with a fireproof clothe. You then rub the solder around the joint allowing it to flow within the joint, rendering it sealed. Wipe away all excess solder and let it cool before testing for leaks.