Alkali metal fluorozincate and method for producing it

#The present invention relates to a method for producing alkali metal fluorozincate, to the resulting product, and to the use thereof in brazing aluminum.

#Alkali metal fluorozincates, such as cesium fluorozincate and particularly potassium fluorozincate, may be used as fluxing agents for brazing aluminum components and components made of aluminum alloys. In this case, these compounds act not only as fluxing agents, but rather they produce a coating of the surface, in that zinc is deposited on the surface of the components. The fluorozincates may also be used together with alkali fluoroaluminates, for example potassium fluoroaluminate and/or cesium fluoroaluminate. These compounds also act as fluxing agents for brazing aluminum. German Published Application 199 13 111 A1 discloses these types of fluxing agents and their use. The production of alkali metal fluorozincates according to this published application is achieved by melting together alkali metal fluoride and zinc fluoride, by reacting alkali metal fluoride and zinc fluoride in aqueous phase, or by reacting zinc oxide with adducts of hydrogen fluoride and alkali metal fluoride.

#It is an object of the invention to provide a method for producing alkali metal fluorozincates which is capable of producing products having defined grain distribution ranges.

#Reaction: KOH+ZnO+3HF−>KZnF3+2H2O

#Batch:

#1) 0.5 ml KOH solution 45.2% w/w 62.3 g ZnO (99.9 cm Aldrich) 40.9 g completely desalinated water (CD water) 30.6 ml 2) HF solution 49.6% w/w 60.6 g CD water 60.6 ml cooling CD water 33 ml