1.3 Flux

Aggressive brazing alloy fluxes based on chloride and fluoride are required to remove the chemically stable aluminium oxide skins. Residue of this flux is hygroscopic and causes corrosion if not removed. It is thus absolutely essential to remove this residue completely from the soldering points. The residue must be washed away using diluted 10% nitric acid and/or hot water. If the flux residue is completely removed, brazed joints have sufficiently good corrosion resistance.

The aluminium brazing flux Silox F 6 S is a white flux powder which is mixed with water to form a white paste before working. The flux tin must be tightly closed after use because the powder is hygroscopic. The life of the flux paste is one working day. If the flux paste is pink, the flux should not be used any more and must be discarded.

The flux corresponds to Type FL-20 in accordance with DIN EN 1045. This flux begins to act at 500 °C and thus has a sufficiently low active temperature range for the Silox S 6 S aluminium brazing alloy.