These are copper-based filler metals, typically formulated as Cu–P or Cu–Ag–P alloys, and are widely used for joining copper and copper alloys. Phosphorus-bearing filler metals produce joints with good electrical conductivity and strong mechanical performance, and they offer excellent corrosion resistance—including resistance to sulfuric acid. However, they are not well suited for brazing ferrous materials such as steel, where joint quality and reliability can be adversely affected.