This solder contains a 2.30-3.20% acid core. Acid core solders are used for soldering materials with poor solderability- Steels, Zinc, Heavily oxidized Nickel, Aluminum, etc. With some exceptions, tin-lead solders can be used to solder copper and most copper alloys, lead, nickel alloys and steel. The 40/60 solder is a general purpose solder used for non electrical applications. It is used for applications in the sheet metal,stained glass, galvanized gutters, and radiator repair industries. The tin-lead solders are not recommended in high stress or vibration joints in the cooling industry due to lack of sufficient elongation properties. This product contains lead and should not be used in potable water systems.