hot dip galvanizing

NUCOR FASTENER
hot dip galvanizing
TECHNICAL DATA SHEET
General
Hot Dip Galvanizing is one of the oldest
methods of zinc coating which involves
immersion of a fastener in molten zinc to
provide a corrosion protecting finish. This
zinc coating provides sacrificial or cathodic
protection to the steel. Because zinc is more
reactive than iron, the zinc galvanized
coating corrodes first, protecting the steel substrate. The appearance of the galvanized surface can vary
from shiny silver to a dull matte gray finish depending upon variables such as the steel composition, rate
of withdrawal from the molten zinc bath and cooling method. The dark gray matte finish will provide just
as much corrosion protection as the shiny appearance. Our domestic sources are qualified and utilize
in-process quality systems enabling us to maintain full traceability from raw material to each container of
product we ship. Chemical and physical certifications are provided with every shipment. Nucor Fastener
is TS16949 and ISO9001 Registered and our laboratory is A2LA Accredited.
The Hot Dip Galvanizing Process
The hot dip galvanizing process starts by carefully cleaning the surface of the steel to prepare it for
galvanizing. After cleaning, the parts are dipped in a flux tank containing (typically) an aqueous solution
of zinc ammonium chloride or they are fluxed by passing through a layer of molten zinc ammonium
chloride floating on the top of the molten zinc. In the galvanizing tank, the parts are completely immersed
in a molten bath consisting of a minimum of 98% zinc. After slowly withdrawing the parts from the molten
zinc, the fasteners are spun in a centrifuge while the zinc is still liquid to remove excess zinc. The parts are
then either air or water cooled to solidify the zinc and to permit handling.
Hot Dip Zinc Coating
The resulting coating from Hot Dip Galvanizing consists of a layer of pure zinc on the outside, with layers
of zinc-iron alloy underneath, ranging from 6% to 25% iron content, leading to the base metal. The
thickness and chemistry of the galvanizing will be principally determined by the bath immersion time, bath
withdrawal rate and the chemistry of the steel being coated. Hot Dip Galvanizing of fasteners is typically
specified to meet the requirements of ASTM A153, Class C (AASHTO M232, Class C); or to ASTM F2329.
The thickness requirements are listed in Table 1.
TDS-007A 2-15-08
TABLE 1 – Coating Weight (Thickness) Requirements
ASTM A153/AASHTO M232/ASTM F2329
FIGURE 1 – Service Life of Hot Dip Zinc Galvanizing
(Source: American Galvanizers Association)
Hot Dip Minimum Weight of Galvanizing oz/Ft2 (Thickness) of Surface
Thickness of Zinc in Micrometers
11
STANDARD & CLASS OF MATERIAL
AVERAGE OF SPECIMENS TESTED
ANY INDIVIDUAL SPECIMEN
1.25 oz/Ft2
(.0021")
1.00 oz/Ft2
(.0017")
ASTM A153, Class C (AASHTO M232)
Fasteners over 3/8" in diameter &
Washers 3/16" or 1/4" in thickness
1.00 oz/Ft2
(.0017")
0.85 oz/Ft2
(.0014")
ASTM F2329
Fasteners & nuts over 3/8" in diameter
Washers 3/16" or 1/4" in thickness
32
43
54
65
75
86
97
ine
ar
lM e
rin
Tro e Ma
t
e ra
mp
a
pic
50
Te
Sub
.0017"
.0015"
al
70
Mo
30
.0017"
129
r
Ru
40
.0020"
118
80
ASTM F2329
Fasteners & nuts 3/8" diameter & under
Washers under 3/16" in thickness
108
60
ASTM A153, Class D (AASHTO M232)
Fasteners 3/8" and under in diameter &
Washers under 3/16" in thickness
21
de
ly
ra t e
Heav
20
ur b
In d
y Ind
an
i
ustr
al
l
ustria
10
0.25
0.50 0.75
1.00
1.25
1.50
1.75
2.00
2.25
2.50
2.75
3.00
4.2
4.7
5.1
Oz. of Zinc/Sq. Ft. of Surface
0.4
0.8
1.3
1.7
2.1
2.6
3.0
3.4
3.8
Thickness of Zinc in Mills
*Service Life is defined as the time to 5% rusting of the steel surface
Special Requirements
Corrosion Protection
Hot Dip Galvanized nuts for structural bolting applications must be heat-treated A563 (AASHTO M291)
While the ASTM/AASHTO specifications do not specify corrosion testing, the life of coating in real world
Grade DH to provide sufficient thread strength to prevent thread stripping, because the nuts are tapped
service will depend upon the actual conditions of the environment. Figure 1 illustrates the typical range of
oversize after galvanizing. Our lubricant containing a green colored dye is put on the HDG coated
service life that can be realized for a variety of environmental conditions.
nuts as a requirement of ASTM/AASHTO specifications to prevent galling during assembly. The visible
dye is a requirement to enable visual confirmation of the presence of a lubricant. The green color of
Nucor Black Kegs are really “Green”! With an Average Recycled Content of 99%, Nucor Fastener products
Nucor Fastener’s Hot Dip Galvanized nuts distinguishes them from our blue dye lubricated Mechanical
qualify for “Green Building” applications or LEED® rated projects. Just as you would expect from Nucor, the
Galvanized nuts to help prevent mixing. There shall be no mixed coating types on structural bolt/nut
largest recycler in North America. It’s our Nature!
combinations per the specifications.
Nucor Fastener has the equipment, quality, systems, expertise, sources & people to meet your specifications.
Testing/Certification Requirements
Testing for the mechanical properties of the fasteners including proof load, wedge tensile strength,
TODAY, THAT LITTLE “n” MEANS BIG THINGS!
and hardness must be done after galvanizing in accordance with the ASTM A325 specification. ASTM
A490, ASTM A490M, ASTM F1852 and ASTM F2280 Structural Products are not permitted to be Hot
Dip Galvanized.
This Technical Data Sheet is subject to change without prior notification.
TABLE 1 – Coating Weight (Thickness) Requirements
ASTM A153/AASHTO M232/ASTM F2329
FIGURE 1 – Service Life of Hot Dip Zinc Galvanizing
(Source: American Galvanizers Association)
Hot Dip Minimum Weight of Galvanizing oz/Ft2 (Thickness) of Surface
Thickness of Zinc in Micrometers
11
STANDARD & CLASS OF MATERIAL
AVERAGE OF SPECIMENS TESTED
ANY INDIVIDUAL SPECIMEN
1.25 oz/Ft2
(.0021")
1.00 oz/Ft2
(.0017")
ASTM A153, Class C (AASHTO M232)
Fasteners over 3/8" in diameter &
Washers 3/16" or 1/4" in thickness
1.00 oz/Ft2
(.0017")
0.85 oz/Ft2
(.0014")
ASTM F2329
Fasteners & nuts over 3/8" in diameter
Washers 3/16" or 1/4" in thickness
32
43
54
65
75
86
97
ine
ar
lM e
rin
Tro e Ma
t
e ra
mp
a
pic
50
Te
Sub
.0017"
.0015"
al
70
Mo
30
.0017"
129
r
Ru
40
.0020"
118
80
ASTM F2329
Fasteners & nuts 3/8" diameter & under
Washers under 3/16" in thickness
108
60
ASTM A153, Class D (AASHTO M232)
Fasteners 3/8" and under in diameter &
Washers under 3/16" in thickness
21
de
ly
ra t e
Heav
20
ur b
In d
y Ind
an
i
ustr
al
l
ustria
10
0.25
0.50 0.75
1.00
1.25
1.50
1.75
2.00
2.25
2.50
2.75
3.00
4.2
4.7
5.1
Oz. of Zinc/Sq. Ft. of Surface
0.4
0.8
1.3
1.7
2.1
2.6
3.0
3.4
3.8
Thickness of Zinc in Mills
*Service Life is defined as the time to 5% rusting of the steel surface
Special Requirements
Corrosion Protection
Hot Dip Galvanized nuts for structural bolting applications must be heat-treated A563 (AASHTO M291)
While the ASTM/AASHTO specifications do not specify corrosion testing, the life of coating in real world
Grade DH to provide sufficient thread strength to prevent thread stripping, because the nuts are tapped
service will depend upon the actual conditions of the environment. Figure 1 illustrates the typical range of
oversize after galvanizing. Our lubricant containing a green colored dye is put on the HDG coated
service life that can be realized for a variety of environmental conditions.
nuts as a requirement of ASTM/AASHTO specifications to prevent galling during assembly. The visible
dye is a requirement to enable visual confirmation of the presence of a lubricant. The green color of
Nucor Black Kegs are really “Green”! With an Average Recycled Content of 99%, Nucor Fastener products
Nucor Fastener’s Hot Dip Galvanized nuts distinguishes them from our blue dye lubricated Mechanical
qualify for “Green Building” applications or LEED® rated projects. Just as you would expect from Nucor, the
Galvanized nuts to help prevent mixing. There shall be no mixed coating types on structural bolt/nut
largest recycler in North America. It’s our Nature!
combinations per the specifications.
Nucor Fastener has the equipment, quality, systems, expertise, sources & people to meet your specifications.
Testing/Certification Requirements
Testing for the mechanical properties of the fasteners including proof load, wedge tensile strength,
TODAY, THAT LITTLE “n” MEANS BIG THINGS!
and hardness must be done after galvanizing in accordance with the ASTM A325 specification. ASTM
A490, ASTM A490M, ASTM F1852 and ASTM F2280 Structural Products are not permitted to be Hot
Dip Galvanized.
This Technical Data Sheet is subject to change without prior notification.
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