Degreasing
Cleaning the galvanized product is the beginning and the most important step of the whole process.
In fact, to ensure the best possible result of galvanizing or other type of galvanization required, the material to be treated must be completely free from impurities which would otherwise be uniformly covered.
The first stage of cleaning products is degreasing: any machining residues, oils, lubricants and greases must be completely eliminated by means of baths containing chemicals which, by emulsion, allow detachment from the object.
Pickling
The pickling phase is necessary to eliminate any residual oxide or rust on the surface of the article through the bath of the same in different acidic solutions at different concentrations.
Rinse
The rinsing phase is a very important step, which must be carried out before the subsequent galvanizing step. In fact, rinsing is necessary to remove any residues of chemicals and oils deposited in the previous cleaning steps.
It is important that the galvanized product comes to the uncontaminated galvanizing phase: on the contrary, if this did not happen, the subsequent treatments and the final result would be compromised, with any defects in uniformity of the protective film and less resistance over time.
It is important that the galvanized product comes to the uncontaminated galvanizing phase: on the contrary, if this did not happen, the subsequent treatments and the final result would be compromised, with any defects in uniformity of the protective film and less resistance over time.
Flushing
The flushing phase consists of immersing the product in a bath formed by a flowing solution, which has the task of preparing the entire surface after the next zinc coating.
Flushing creates a thin film of saline on the entire surface, which allows to lower surface tension and facilitate wetting between the two different metals.
The flow also protects the surface from oxidation when waiting for the next step.
Flushing creates a thin film of saline on the entire surface, which allows to lower surface tension and facilitate wetting between the two different metals.
The flow also protects the surface from oxidation when waiting for the next step.
Drying
The metal pieces that need to be galvanized later, go through a drying oven whose task is to preheat the articles themselves in order to reduce the thermal shock at the galvanic bath.
Galvanization
It’s the step where the metal piece actually receives the required protective layer. The metal product can receive 2 different types of galvanization according to the characteristics and dimensions of the workpieces to be treated: hot galvanizing or cold galvanizing.
Hot galvanizing: The artifact, hanging, is lowered and immersed in the molten zinc bath (in the case of galvanization, the temperature is about 450 °). It remains fully immersed for a time varying between 5 and 20 minutes according to the characteristics of the same.
Cold galvanizing: The artifact is hung, positively charged and immersed in a chemical bath where the protective material is present which, negatively charged, is attracted to the article and distributed evenly throughout the surface.
Hot galvanizing: The artifact, hanging, is lowered and immersed in the molten zinc bath (in the case of galvanization, the temperature is about 450 °). It remains fully immersed for a time varying between 5 and 20 minutes according to the characteristics of the same.
Cold galvanizing: The artifact is hung, positively charged and immersed in a chemical bath where the protective material is present which, negatively charged, is attracted to the article and distributed evenly throughout the surface.
Cooling
In the cooling phase, the artifacts are extracted from the galvanic bath and the excess material is drained. It is a very critical phase because it is important to avoid the formation of drips which would compromise the final result.
Metal pieces, though no longer immersed in the galvanizing bath, are still at high temperatures and the chemical process continues. To stop the process being processed, the artefacts are cooled with a mixture of air and water.
Metal pieces, though no longer immersed in the galvanizing bath, are still at high temperatures and the chemical process continues. To stop the process being processed, the artefacts are cooled with a mixture of air and water.
Passivation
The passivation treatment causes the outer layer of the protective film, the one in contact with atmospheres, to react much more slowly in contact with air and other natural elements.
The treatment is needed to avoid the so-called “white rust” that would form and compromise the aesthetics of building-architectural constructions, for example. It is to be specified, however, that this “white rust” does not absolutely affirm the strength and effectiveness of the underlying protective film.
With the passivation process, galvanizing treatment can be considered complete.
The treatment is needed to avoid the so-called “white rust” that would form and compromise the aesthetics of building-architectural constructions, for example. It is to be specified, however, that this “white rust” does not absolutely affirm the strength and effectiveness of the underlying protective film.
With the passivation process, galvanizing treatment can be considered complete.
This post is also available in: Italian