Canadian Finishing & Coatings Manufacturing Magazine September/October 2021 - 30

PLATING AND ANODIZING: GALVANIZING
Hot-Dip
Galvanizing
for a
Sustainable
Future
protection systems.3
BY ALANA FOSSA
F
or more than 150 years, hot-dip galvanizing after
fabrication has been a proven technology in combating
steel corrosion with a protective coating of zinc.
Often considered a rugged or unpolished coating
system, hot-dip galvanizing is an essential option for specifiers
in need of an affordable and maintenance-free coating for steel
structures in harsh environments. However, many specifiers are
surprised to learn of widespread applications throughout Canada
where hot-dip galvanizing is increasingly identified to achieve
versatile designs in the pursuit of constructing resilient and
sustainable structures. Innovative and proven applications are
found throughout Canada's bridges, transit facilities, recreation
centers, parking structures, buildings, and more.
After fabrication, hot-dip galvanizing (HDG) is a coating
process where steel is cleaned and then immersed in a bath of
molten zinc. The result is the formation of a metallurgically
bonded coating comprised of intermetallic alloy layers and often
an outer layer of pure zinc. Unique in comparison to concrete,
wood, stone, or corrosion-resistant steels, this protective barrier
coating also protects steel cathodically, meaning zinc sacrificially
corrodes to protect the base steel1
.
Another key aspect that differentiates HDG from other
construction materials is its longevity in atmospheric
environments. Using real-world corrosion data, coating life is
estimated using the American Galvanizers Association (AGA)
Time-to-First Maintenance (TFM) chart (Figure 1). As the TFM
chart shows, a common coating thickness requirement of 100 -m
[3.9 mils] provides a minimum of 72 years before maintenance in
an industrial environment, or greater for other environments.2
Because HDG remains maintenance free for many decades, the
life-cycle cost is often the same as the initial cost, representing
significant savings while also remaining competitive on an initial
basis with other construction materials and steel corrosion
30
www.cfcm.ca
A life-cycle cost calculator is available at
lccc.galvanizeit.org to input specific project details and compare
HDG cost to the published costs of more than 30 other corrosion
protection systems. 4
Though excellent corrosion resistance and reduced lifecycle
costs are inherent when hot-dip galvanizing, HDG steel
is increasingly recognized for its ability to assist with other
project requirements including quick turnaround times, low
maintenance, versatility, sustainability, and aesthetics. This
is showcased in innovative projects throughout Canada where
hot-dip galvanizing highlights one or more of these benefits for
a variety of industries. In particular, such benefits have offered
elegant solutions for many of Canada's infrastructure needs.
The Olivier-Charbonneau Bridge is a six-lane, 1.2-km
cable-stayed and steel-girder
combined
bridge
connecting
Henri-Bourassa Boulevard in Montreal to Autoroute 440 in
Laval (Figure 2). As the first public-private partnership project
of its kind in Quebec in 2011, the demand for strict governmental
standards, maintenance-free longevity, and a low life-cycle cost
to ensure company profit was a significant challenge.
Hot-galvanized bridges have demonstrated long-term
performance in Quebec since 19635
. This paved the way for
its specification as an affordable means to protect against
Quebec's cold, humid and rigorous winter weather on every
100
10
20
30
40
50
60
70
80
90
1.0
1.5
2.0
2.5
3.0
3.5
Average Thickness of Zinc (mils)
*Time to first maintenance is defined as the time to 5% rusting of the substrate steel surface.
4.0
4.5
5.0
1 mil = 25.4µm = 0.56oz/ft2
The Time to First Maintenance Chart shows the anticipated longevity
of the hot-dip galvanized coating in various atmospheric environments,
based on the coating thickness. The chart was developed
based on actual corrosion rates in the field.
Key
Rural
Suburban
Temperate Marine
Tropical Marine
Industrieal
Time to First Maintenance* (years)
http://lccc.galvanizeit.org http://www.cfcm.ca
Canadian Finishing & Coatings Manufacturing Magazine September/October 2021

Table of Contents for the Digital Edition of Canadian Finishing & Coatings Manufacturing Magazine September/October 2021
