GalFan ZGF 255 expected design life 50yrs to 150yrs
The estimated time to first maintenance for a
hot-dip galvanized coating that experiences common atmospheric exposure can be
seen below. Time to first maintenance is defined as the time to 5% rusting of
the substrate steel. The time to first maintenance of hot-dip galvanized steel
is directly proportional to the zinc coating thickness. Source American
Galvanisers Association
www.galvanizeit.org
1.5mil = 255grams/m2 = ZGF255 spec
GalFan (95% zinc, 5% aluminium) has proven to be 2 to 3 times more corrosive resistant than the same thickness of Hot Dip 100% zinc Galvanising. Depending on the environment, it may take 50yrs to 150yrs for 5% rust to show on the surface of GalFan ZGF 255 spec, when above ground.
AS / NZS 4534 Zinc and zinc/aluminium-alloy coatings on steel wire. Class W10 (heavy coating)
When constructing gabion retaining walls in strongly acidic soils (PH over 5.5), the soil and the corrosive groundwater must be separated from the gabion structure by using geotextile fabrics and a properly designed drainage system.
Good drainage behind and below your gabion retaining wall will not only improve the retaining walls stability, it will also increase the expected design life of the gabion wall
Below is a link to link to a 15 year long study on factors that effect the life span of gabions
State of California Gabion mesh corrosion report
SPECIAL ENVIRONMENTS
In
New Zealand there are areas where local conditions create an increased
likelihood of corrosion.
Special consideration should be given to material selection and design in these
areas. They include:
1.
Geothermal Areas
Hydrogen sulphide associated with geothermal activity creates a corrosive
environment. Variations in
natural activity or draw-off from steam bores plus the effects of weather
conditions make the high risk areas
hard to define.
2.
West Coast, South Island
In
this area, smoke from the coal burning fires may cause high concentrations of
sulphur dioxide in the air.
The combination of this and the high rainfall for the region creates an
aggressive situation which must be
considered . The effects of a severe coastal environment aggravate the
situation. This
area combines the most severe features of both industrial and coastal
environments.
3.
Coastal Environment
Within 1000m of the coast, characterised by:
Light salt deposits
A frequent smell of salt in the air
In the immediate vicinity of large expanses of calm salt water such as harbour foreshores
This environment may be extended inland by prevailing winds and local conditions.
4.
Industrial Environments
Within 500m of corrosive industrial emissions and subject to heavy fallout from them.
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