the wetter it is, the more salts are generated. Instead, in a dry environment the zinc is
passivated; this means that a film forms on
the metal surface which protects it against
external factors. So the zinc becomes more
resistant and stable, a constant exchange of
wetting and drying cycles is needed, meaning this metal is optimal for outdoor use.
Conversely, if the profiles are permanently
in a humid environment, that is when the
zinc salts appear, starting the oxidation and
deterioration.
The relative humidity of the frozen storage is, in theory, practically zero, only being
found in the entrances and exits of the
warehouse. That is why galvanized racking
is a perfect fit. However, humidity is higher,
even necessary, in cold storage. For this reason, the installation of galvanized racks in
this kind of cold storage is a mistake: passivation will protect the entire structure for a
few months, but once it loses its effectiveness, the zinc will decompose forming zinc
salts and disappear.
In fact, during tests in a salt fog chamber, it
can be seen that the behavior of hot-rolled
galvanized material is much worse. By not
being passivated, its deterioration occurs in
under 100 hours and pre-galvanized sheet
metal at around 150 hours. This test is applicable when determining the comparative
anti-corrosive quality of various types of
coatings.
Above: results from tests of different finishes in a salt fog chamber for a period of 100, 400, 700
and 1,000 hours.
Below: view of some tests in a salt fog chamber
CATA
100H
CATA+POWDER
100H
POWDER
100H
GALVA
100H
CATA 700H
CATA+PO WDER 700H
POWDER 700H
CATA+PO WDER 400H CATA 400H
POWDER 400H
GALVA 400H
CATA
1000H CATA+POWDER
POWDER
1000H
GALVA 700H GALVA 1000H
