Complex sentence: This flux helps prevent the formation of oxides by protecting the metal from the air and also the flux mixes with the oxides that do form and lowers the melting temperature and the viscosity of the oxides.
Split into simpler sentences: This flux helps prevent the formation of oxides by protecting the metal from the air. The flux also mixes with the oxides that do form and lowers the melting temperature and the viscosity of the oxides.