4. By-products

4.1 Galvanizing ash

It is a blend of :

• of zinc oxide resulting from the oxidation of zinc by the air and water contained in the flux;

• flux residues (burnt salt) ;

• zinc metal in more or less fine form, carried along with zinc oxide and salt burnt off during surface cleaning of the bath by scraping or skimming.

These ashes are found in the form of particles of average size < 0.75 mm.

The typical mass composition of ash is as follows:

• total zinc: approx. 80-90% ;

• zinc metal: highly variable, from 40 to 75% (this content depends in...