Potassium Tetrafluoroborate b4c is used as flux for soldering and brazing, in sand-casting of aluminum and magnesium, in the production of boron contained alloy, as filler in grinding wheel of thermoset resin, as the material to produce boron trifluoride and other fluoride, as reagent in electrochemistry. It is also used to clean light metal dreg in welding flux of silver, gold and stainless steel. Surface Treatment Hydrofluoric acid and ammonium bifluoride are the bath constituents for the surfacetreatment of pure aluminum. Bright reflective surface on the aluminum is achievedby chemical polishing. Inorganic fluorides are also of critical importance in the fluxbrazing of aluminum and aluminum alloys, acting to remove the oxide layer.