Most of the processes are essentially passive anticorrosive: coat the steel with a tin coating isolating it from the surrounding environment.
Once the coating is damaged rust appears that propagates rapidly eroding the structure that deteriorates progressively.
La zincatura a spruzzo, Unlike, It offers active protection because zinc acting as an anode protects the iron (cathode) sacrificing herself in his place. It 'a simple and rapid technique based on the arc where electric two zinc wires are melted in a myriad of particles immediately projected by a jet of compressed air on the pre-cleaned support(no presence of VOC volatile organic components). In addition to zinc spraying aluminum, brass copper, inox, etc.. The zinc deposited thickness depends on the number of passes made by the operator and ranging from 40um to 500 one (no other protective system can achieve these high levels). The higher the thickness of zinc is the longest duration of protection against rust that may exceed 70 years or more without the need for costly periodic maintenance.
Consider the following corrosion rate :
| atmosphere |
corrosion rate (um / year) |
||
|
steel |
zinc |
aluminum |
|
| rural |
5-10 |
0,85-1,4 |
0,1 |
| urbana |
10-30 |
2,70-16 |
1 |
| heavy industrial |
30-60 |
2,00-16 |
1-3 |
| marina |
10-30 |
1,00-8 |
0,4-0,6 |
the designer is able to know from the outset what is the thickness of zinc necessary to ensure the artifact an average life before it appears the 5% of red rust on the surface.
for the designer reminder :
a) Establish the nominal life (NTC technical standards Construction-Circular February 2008) and identify the durability of anticorrosive systems (EN ISO 2063:2005 thermal spray)
b) Identify and classify the corrosivity of the environment and minimum thickness UNI EN ISO 2063:2005 (B)
c) Preventive sandblasting of the support UNI EN ISO 11124-2, 11126-3, 11126-7
d) Painting of galvanized (effect duplex) for aesthetic reasons and / or prolong duration EN ISO 12944- 5 UNI EN 13438:2006
and) Extraordinary maintenance, is reached when the degree of rusting Ri3 (1% of the protected area)
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