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Introduction
Arguably one of Australia’s harshest environments
(and one of heaviest populated) is our coastal environment.
These areas often have a very high level of soluble
chlorides which is very detrimental to the long-term
life of steel.
Hot dip galvanized coatings have been used as a successful
steel protection system over many years in these environments.
Industrial Galvanizers is committed to ensuring that
we are aware of the performance of our coatings in
all types of environments, including our harsh coastal
conditions.
The Areas Tested
In order to study the amount of corrosion on the
hot dipped galvanized coating, three sites on Queensland’s
Gold Coast were tested. These sites were first tested
on 24 February 1999, with the same sites being re-tested
by our staff on 14 September 2000.
All of the sites tested were no more than 100 metres
from a surf beach, with all surfaces tested being
those fully exposed to the sea.
What Was The Original Thickness?
The minimum coating mass of a galvanized coating
has been specified in the Australian Standard for
Hot Dip Galvanizing AS 4680-1999. This is dependent
on the section thickness of the steel being coated
and expressed as mass/m2, then converted
to coating thickness in microns for ease of measurement.
In this test, rather that using the standard as a
starting point reference for coating thickness, the
exact same sites over an 18-month period. This enables
the exact corrosion rate for each particular site
to be extablished.
In both instances, coating readings were taken using
a Elcometer 345 electronic digital coating thickness
gauge.
The Results
The results obtained from all three sites are in
the following table. A full copy of the report is
available from Industrial Galvanizers upon request.
| Location |
Product |
Thickness on
24/02/1999 |
Thickness on
14/09/2000 |
Difference |
| Geoffrey Cornish W/Way |
75 NB Pipe |
52.3 |
51.3 |
-1.0 |
| Broadbeach Blvd. |
Pole Nail
10mm FMS |
114.7 |
112.0 |
-2.7 |
| Light Pole |
Tapered Pole
5mm |
128.7 |
124.9 |
-3.8 |
| NB: All thickness readings
are the average of ten readings taken |
We can therefore conclude the following life expectancy,
not including the trouble free life already given:
| Location |
Coating loss
per annum |
Thickness |
Life expectancy
|
| Geoffrey Cornish W/Way |
0.6667 |
51.3 |
77 years |
| Broadbeach Blvd. |
1.8000 |
112.0 |
62 years |
| Light Pole |
2.5333 |
124.9 |
49 years |
Conclusion
The performance of the coating in such a harsh and
corrosive environment is a tribute to the benefits
of hot dip galvanizing. Maintenance free life expectancy
not only saves high in-situ refurbishment costs, but
also results in the project owners not having any
anxiety over maintenance issues. They can rely on
hot dip galvanizing! |
