The longevity of a galvanized coating is directly proportional to the thickness of the layer of zinc that covers the structures. It is influenced by the quality of the environmental conditions it is exposed to and whether or not there is any acid pollution in the air surrounding it. The thickness of the coating usually ranges from 50 to 100 microns or more. Its longevity is related to its predicted corrosion rate which, in normal environmental conditions, is around 1 micron per year.
A coating can therefore be expected to have a minimum lifespan of 40/50 years or more, in normal applications.
La zincatura a caldo è un trattamento che offre grande affidabilità attraverso la protezione esterna e interna del manufatto il che garantisce la massima sicurezza per tutte le strutture che non possono essere ispezionate agevolmente oppure nel caso di elementi soggetti a condizioni di utilizzo impegnative come possono essere i ponteggi o le gru per edilizia e le attrezzature in genere.
Hot galvanizing is a highly reliable treatment due to the fact that it provides fabricated articles with protection in both indoor and outdoor conditions. This guarantees the highest level of safety for those types of structures which cannot be easily inspected or for items subjected to harsh conditions of use, such as scaffolding, construction cranes and other types of tools and equipment.
A coating formed in this manner cannot come detached. Even small scratches caused by accidental impacts or damage caused during transport or assembly are protected, thanks to the sacrificial action of the zinc.
It is important to remember that the destructive action of rust does not always manifest in such a way as to be evident. Often, beneath an apparently intact layer of paint, a dangerous piece of rotten iron could actually be hiding (remember the cars of the not-so-distant past?).
UNI EN ISO Standard 14713 lists the average loss of thickness of zinc coatings in different environmental condition categories.
The zinc thickness loss values given in the table refer to the first 90 years and, since air quality has continuously improved since that time, we can safely state that today's corrosion rates are much lower than the historic data shown in the table.
UNI EN ISO Standard 1461 calls for a minimum zinc coating thickness that varies based upon the thickness of the material used.
Thickness of the material:
For hot galvanized structural shapes, real values are actually much greater than 100µ in thickness.
Corrosion resistance can be further improved by proper painting subsequent to hot galvanizing (the Duplex system). This protection method is capable of doubling the sum of the lifetimes of the individual zinc and paint coatings.