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3. How does
the cost of hot-dip galvanizing compare to
other corrosion protection systems, such as
paints?
When compared with paint systems,
hot-dip galvanizing after fabrication has
comparable initial application costs and,
almost always, lower life-cycle costs. In
fact, the lower life-cycle costs of a hot-dip
galvanized project make galvanizing the smart
choice for today and tomorrow.
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4. Does the
galvanized steel coating of zinc resist abrasion?
The three intermetallic layers that
form during the galvanizing process are all
harder than the substrate steel and have excellent
abrasion resistance.
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5. What causes
wet storage stain and how can it be prevented?
Zinc on newly galvanized steel is very reactive
and wants to form zinc oxide and zinc hydroxide
corrosion products that eventually become
the stable zinc carbonate. When galvanized
steel is tightly stacked or stored in wet
boxes that don't allow for free flowing air,
the zinc forms excessive layers of zinc hydroxide,
otherwise known as wet storage stain. Most
wet storage stain can be easily removed with
a cleaner or nylon brush. To prevent wet storage
stain, store galvanized steel indoors or block
it so that there is ample free flowing air
between each galvanized article.
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6. What
are the specifications governing hot-dip galvanized
steel?
| |
Designation |
Title of Standard |
| Galvanizing
Standards |
| Australia/New Zealand |
AS/NZS 4680 |
Hot-dip galvanizing (zinc)
coatings on fabricated ferrous articles |
| Canada |
CAN/CSA G164 |
Hot dip galvanizing of irregularly
shaped articles |
| South Africa |
SABS/ISO 1461 |
Hot dip galvanized coatings
on fabricated iron and steel articles |
| Europe |
EN ISO 1461 |
Hot dip galvanized coatings
on fabricated iron and steel articles |
| International Standards
Organization |
ISO 1461 |
Hot dip galvanized coatings
on fabricated iron and steel articles |
| Reinforcing
Steel Standards |
| United States |
ASTM A 767 |
Zinc-coated (galvanized)
steel bars for concrete reinforcment |
| France |
NF A35-025 |
Hot dip galvanized bars
and coils for reinforced concrete |
| Italy |
UNI 10622 |
Zinc-coated (galvanized)
steel bars and wire rods for concrete
reinforcement |
| India |
IS 12594 |
Hot-dip coatings on structural
steel bars for concrete reinforcement
specifications |
| International Standards
Organization |
ISO 14657 |
Zinc-coated steel for the
reinforcement of concrete |
| Europe |
prEN EC019023 |
Steel for reinforcement
- Galvanized reinforcing steel |
| Reinforcing
Steel Specifications |
| Germany |
Z-1.4-165 |
Allgemeine Bauaufsichtliche
Zulassung - Feuerverzinkte Betonstahle
General approval by the building authorities
- Galvanized reinforcing steel |
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7. What
if the article to be galvanized is larger
than the dimensions of the galvanizer's kettle?
Can it still be galvanized?
Galvanizers can progressively dip
such a fabrication or article of steel. They
dip one half in the molten zinc bath, remove
it, turn it around or over and immerse the
other half in the zinc. This method is often
erroneously referred to as 'double dipping'.
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8. Where
are galvanized steel products used?
First of all, the variety of things galvanized
is broad. Structural steel (angles, channels,
wide-flange beams, I-beams, H-beams), grating,
expanded metal, corrugated sheets, wire, cables,
plate, castings, tubing, pipe, bolts &
nuts. The industries that utilized hot-dip
galvanized steel range from bridge & highway
(reinforcing steel for decks and column concrete,
girders, stringers, light and signposts, guardrail,
fencing), water & wastewater treatment
plants (walkway grating/expanded metal, handrails)
architectural (facades, exposed structural
steel, lentils), parking garages (reinforcing
steel for concrete decks, exposed structural
steel columns and barriers), pulp & paper
plants (structural steel, walkways, handrail),
OEMs (motor housings, electrical cabinets,
frames, heat exchanger coils), electrical
utilities (transmission towers, distribution
poles, substations, wind turbine poles), communication
(cell towers), rail transportation (poles,
switchgear, miscellaneous hardware), chemical/petro-chemical
(pipeline hardware, manufacturing buildings,
storage tanks, walkways), recreation (boat
trailers, stadiums, arenas, racetracks), and
many more.
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9. Sometimes,
the galvanized coating is shinier in some
places than others. Why is that?
The galvanized coating appearance may either
be bright and shiny resulting from the presence
of an outer layer of pure zinc, or duller,
matte gray as the result of the coating's
intermetallic layers being exposed. Performance
is not affected. Coating appearance depends
on the amount of zinc in the coating.
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10. I'm
interested in specifying hot-dip galvanizing
for reinforcing steel. Are there any concerns
with fabricating rebar after galvanizing?
Rebar is commonly fabricated after galvanizing.
In order to minimize the possibility for coating
damage, avoid bending the rebar at a radius
of less than 8 times its radius. ASTM A 767,
Specification for Zinc-Coated (Galvanized)
Steel Bars for Concrete Reinforcement, has
a table that provides maximum bend diameters
for various-sized rebar.
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