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Volume 8,
Issue 1 |
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Bridge and Highway construction to
increase five percent. |
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2008 Construction
Outlook
Based on the 2008
construction outlook from McGraw Hill Construction, all sectors of
construction including residential, non-residential, and
non-building will decline two percent in the US (in millions of
dollars) in total volume. The decline can be defined by the sharp
drop in single-family housing construction because of the sub-prime
mortgage crisis, stricter lending standards, and higher interest
rates. This downturn affects all parts of the construction industry,
including commercial real estate and property development. Amid the
lack of growth, several sectors including institutional buildings
and public works construction will see a modest increase as will an
emphasis on “green” construction practices. Also on the positive
side, public financing will remain in place for infrastructure
projects with transportation and bridge construction in response to
the Minneapolis bridge accident.
> MORE
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 Q:
Do "cold galvanizing"
and hot-dip galvanizing provide equivalent corrosion protection?
The simple answer
is no. Zinc, used to protect steel from corrosion, is applied by
many methods. The two most popular methods are zinc-rich paint (ZRP)
and hot-dip galvanizing (HDG). Often times, ZRP is referred to as
"cold galvanizing," and is viewed as an equivalent coating to HDG
because of a belief that all zinc coatings "galvanize." This is an
incorrect assumption.
The term
galvanizing, from a definition standpoint, means a metallurgical
reaction between the iron in steel and the molten zinc occurs during
the hot-dip galvanizing process. The HDG coating forms a series of
zinc-iron alloy layers, composed of three alloy layers and a top
layer of pure metallic zinc. The HDG coating is bonded to the
underlying steel with an adhesive strength of approximately 3,600
psi and is impermeable to corrosive elements. The metallurgical
reaction forms perpendicular to the steel surface and produces
consistent coating thickness on all corners and edges as well as
flat surfaces. Also, because the steel is completely immersed, it is
coated on all interior and exterior surfaces, and thus thoroughly
protected with barrier and cathodic protection. Zinc is anodic to
steel and preferentially corrodes very slowly to protect the
substrate steel. Furthermore, over time the HDG coating develops an
insoluble patina of zinc carbonate that inhibits corrosion and
offers 50 to 80 years of protection without maintenance.
> MORE
For more information,
DOWNLOAD the AGA publication Hot-Dip Galvanizing vs.
Zinc-Rich Paint. |
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The AGA is a non-profit trade
association focused on providing education and technical support for
architects, engineers, and specifiers. For more information about the
AGA, visit www.galvanizeit.org. Out of respect for your privacy, we do
not sell or rent our lists with any other parties. If you do not wish
to receive Galvanizing Insights, you may cancel your complimentary
subscription by using the link below.
This official publication of the
American Galvanizers Association, Inc. (AGA) does not necessarily
reflect the view of the board of directors or AGA members. Every
effort is made to ensure accuracy. Any errors are strictly accidental
and may be corrected in a subsequent issue. This material provides
general information only and is not intended as a substitute for
competent, professional examination and verification as to suitability
and applicability. The publication of the material herein is not
intended as a representation or warranty on the part of the AGA.
Anyone making use of this information assumes all liability arising
from such use. Questions or comments about this publication should be
directed to the AGA. Comments and suggestions are encouraged.
Copyright © 2008
American Galvanizers Association. The material provided herein has been
developed to provide accurate and authoritative information about
after-fabrication hot-dip galvanized steel. This material provides
general information only and is not intended as a substitute for
competent professional examination and verification as to suitability
and applicability. The information provided herein is not intended as a
representation or warranty on the part of the AGA. Anyone making use of
this information assumes all liability arising from such use.
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