Flux Regeneration

With the evolved methods of today, where the steel is only etched on the surface, the fluxing have a broader meaning. Through the safety margin, as is composed for the iron/zinc-reaction, it also has become a buffer and a guarantee that no iron is added to the zinc melt.

The flux coating also has a meaning when the goods are stored in a buffer zone before galvanization, since it gives a good protection against corrosion.

Because of this it is of greatest importance that the flux system is shaped so that it can perform a firsthand total reduction of all iron added from rinse tubs, light grazing or that which is released from the goods in the flux bath.

The parameters that a well working flux system has to fulfill is:

  • Iron must continuously be reduced from the bath until it is below 1 g/l
  • Sludge and impurities must be reduced continuously
  • Flux salts must be kept at an exact, pre-determined, level
  • Neutral salt value should not exceed 10 g/l
  • The pH value should be at 4,5
  • The temperature should always be kept at a previously decided point
  • Neutral salt content should be trimmed in so that it reaches the right reaction speed between iron/zinc
  • The flux coating must be dry when added to the zinc melt in order to stop release of iron from the goods

The flux bath holds two salts, zinc chloride and ammonium chloride, that will protect against corrosion and simplify the iron-zinc alloy.

In the process it is a constant release of FeCl2 from the grazing baths. When FeCl2 is pulled over to the zinc bath, each part of the iron binds up to 25 parts of zinc and forms what we call “dross” or hard zinc.

In the continuous flux regeneration we use peroxide to oxidize Fe to Fe(OH)2. Automatic dosing of ammonia catches the free chloride ions and builds ammonium chloride. From the zinc deduction bath we recycle zinc chloride.

The iron hydroxide sludge is filtered out through a filter press and keeps the value of Fe down to under 1 gram per liter flux.