The pre-treatment operations required to clean the pieces to be galvanized are carried out by dipping the materials into a series of degreasing, pickling, washing and fluxing tanks. The tanks lie on a basin, perfectly sealed to prevent accidental leaking, and are included in a fully sectioned tunnel, equipped with an acid fume extraction and reduction system, protecting the work environment and constantly keeping under control the emissions into the atmosphere. The whole system is self-contained and has no external exhausts. The treatment solutions are heated by a system which recovers the heat released by the galvanized product cooling tank. The presence of redundant treatment stations and the mechanical handling of the materials to be treated allow to drastically reduce the solution concentration, allowing to save raw materials and reducing the production of acids and exhausted solutions to be disposed of. Operation management is fully automated, with definite and pre-determined immersion and dripping times, avoiding unwanted solution consumption and drag-out. The pickling solutions also include corrosion inhibitors and products that further increase their efficiency, reducing the consumption of acid. The subsequent washing is performed in a tank of water which is continuously de-ironed to limit the unwanted drag-out of the dissolved iron to the galvanizing tank; this strongly limits, during the galvanizing stage, the production of bottom mattes which then need to be recovered. The flushing fluid includes products allowing to reduce the usage concentration, thus reducing the production of zinc ash, while helping the subsequent galvanising of the materials by the HAl-Ga ® technology.

 

 

The materials, cleaned free of grease and rust and protected by a thin coating of flushing products, are moved into an automatic feeding 4-station drier; the latter is directly connected to the pre-treatment tunnel and is basically heated by the hot fumes leaving the galvanising furnace.
The system automatically controls the weight of the materials that are to be sent to the preheating stage; this allows to properly feed the galvanising furnace, avoiding unnecessary operating temperature fluctuations, which may affect gas consumption.
A similar flow prediction system automatically manages the access of the materials to the pre-treatment tunnel.
The large size of the drying chamber allows for the materials to remain in it for a longer time and for the pre-heating temperatures to be reached with certainty; this ensures, in the subsequent galvanising stage, important gas savings and a limitation of the production of skimming and zinc ashes which then need to be recovered.

 

 

The new latest generation furnace, enveloping and heating the galvanizing tank, is fuelled by natural gas and is of high-speed type, with controlled stratification of the tank bottom section temperature.
Compared with traditional furnaces, performances being equal they allow considerable gas savings and prolong the tank life.

 

 

The galvanizing tank is equipped with an extraction booth, fitted with a fabric filter allowing to fully extract and reduce the white fumes generated by the dipping of the materials into the zinc, thus drastically reducing the emissions into the atmosphere.
For the filling and topping up of the galvanizing tank we only use 99.995% SGH-type initial melting hyper-pure zinc and technological alloys bringing the content of zinc in the tank down to at least 99.7%. No metals regarded as "dangerous" to people and the environment, like Lead and Nickel, are used in the galvanizing bath.
The production of slag and by-products, like skimming ash and bottom mattes has been reduced by the adoption of the measures listed above.

 

 

The HAl-Ga ® patented technology, used to control steel reactivity, was implemented during the year 2008.
This allowed to easily eliminate the use of metals regarded as “dangerous” to people and the environment, like Lead and Nickel, in the galvanizing bath, while also allowing to considerably reduce the zinc consumption.

 

 

The Chrome-free passivation cycle was implemented by ZIMETAL, for the first time in Italy, in 1995; the galvanized materials are first cooled in water and then dipped into the passivation solution.
The heat released by the galvanized materials, through an exchanger system, fully covers the supply requirements of the pickling stage heating systems.
Passivation helps limiting the formation and the uncontrolled release of zinc corrosion products.