When to Use Fluxes?

In soldering, a flux is used to remove oxide films, promote wetting, and prevent reoxidation of the surfaces during heating. Rosin is widely used as a noncorrosive flux in soldering electronic equipment; for other purposes, a water solution of zinc chloride and ammonium chloride may be used.

Do I need to use flux when soldering?

Yes, solder can be used without flux. To do so, you will need something other than flux to break down the oxides on the metal surface, without which your surface may be damaged or not properly cleaned.

How do you use flux to solder?

Use a small paintbrush or your fingers to scoop up a small amount of soldering flux. Spread the flux over the area you will be soldering, making sure to cover the wires fully. Wipe any excess flux off your fingers or brush before soldering. Soldering flux is only corrosive once it is heated up and in its liquid form.