F2329 specification covers the requirements for hot-dip
zinc coating applied to carbon steel and alloy steel bolts,
screws, washers, nuts, and special threaded fasteners. It also
provides for minor coating repairs. Nails and rivets are not
included in this specification.
It is intended to be applicable to fasteners that are
centrifuged or otherwise handled to remove excess galvanizing
bath metal (free zinc).
Orders for zinc coating of fasteners to this specification shall include the following:
1. Name of product (that is bolt, stud, nut, washers, or other);
2. ASTM designation and year of issue, including fastener specification number;
3. Hydrogen embrittlement relief treatment, as required by the purchaser
4. Quantity of fasteners to be hot-dip zinc coated;
5. Stress relief or tempering temperature to which the fasteners where subjected, if applicable;
6. Secondary processing such as chromating, phosphating, or lubrication, if applicable;
7. Average galvanizing temperature to which fasteners will be subjected, if required by the
purchaser.
8. Specify baking if required and
9. Certification, if required
10. Supplementary Requirements (See S1).
1. Condition of the As-Received Fasteners — The fasteners as received by the galvanizer shall be free
from contaminants that are not readily removed in the cleaning process and would adversely affect the
galvanizing.
2. Process—Unless otherwise covered in this specification, all processing parameters shall be in
accordance with the requirements of Specification A153/A153M. Process Control—Galvanized fasteners subjected to a
process control
plan based upon batch lot level shall comply with the batch lot sampling plan in below Table, and the
sampling plan for production lot (prevention process) as determined in 10.2.2 shall
be applied.
3. Spinning and Quenching:
Parts shall be spun immediately following removal from the galvanizing bath and quenched in water. In
addition, small parts shall be air cooled, as needed, in order to prevent the formation of zinc oxide.
Parts, which cannot be spun shall be brushed or handled otherwise to remove the excess zinc
| Sample Size B | |||
|---|---|---|---|
| Batch Lot Size | Average Coating Thickness c | Adhesion | Apperance D |
| 5 to 25 | 1 | 1 | 1 |
| 26 to 50 | 1 | 1 | 2 |
| 51 to 150 | 2 | 1 | 2 |
| 151 and over | 2 | 2 | 2 |
A The acceptance criterion in all cases is zero defects.
B The sample size is the number of specimen(s) required to be tested/inspected to the applicable
criteria.
C Frequency of coating thickness measurements: one set of specimen(s) for every
five batch lots. For test method, see 11.1
D Visual inspection for conformance.
4. Alteration of Threaded Fasteners:
Fasteners that have been hot-dip galvanized shall not
be further altered (such as subjected to a cutting, rolling, or
finishing-tool operation) by the galvanizer unless specifically
authorized in writing by the purchaser. Hot-dip galvanizing of externally threaded fasteners
shall meet the thread fitting requirements of the specified
product standard or specific allowance as determined by the
customer.
NOTE 1—The scope of this specification does not cover the requirements
regarding the overtapping of galvanized nuts. These requirements
are established by the applicable product standard, such as Specification
A563, Specification A563M, (or others), or in
writing by the purchaser, if needed.
5. Secondary Processing:
When requested by the purchaser, treatments such as chromating or phosphating shall be applied to
reduce the possibility of wet storage staining (white corrosion) or to assist subsequent painting.
When specified on the purchase order, the nuts, bolts, or screws shall be lubricated to enhance
assembly.
6. Touch-up and Repair—Bare, cut, or damaged spots found on fasteners after galvanizing, totaling less
than 1% of the coated surface area, may be repaired with paints containing zinc dust. Such paints
shall have zinc-dust concentrations of 65 to 69% or concentrations above 92% in the dried film. The
repairing party shall select the paint and follow its application instructions. The applied coating
shall provide barrier protection, and preferably be anodic to steel. Thickness measurements of
repaired areas shall not be required.
NOTE 2—Experience shows that, in general, organic zinc-rich systems
are tolerant of marginal surface preparation and are not critical of
climactic or atmospheric conditions for curing. Corrosion resistance and
service performance are very dependent on the properties of the paint
system, the extent of surface preparation, and the skills of individual
applicators. See Practice A780/A780M.
Unless otherwise specified in the product standard, the zinc used for the coating shall conform to the requirements of the section on Zinc of Specification A153/A153M.
1. Stress Relief—Fasteners subjected to severe work hardening shall be stress-relieved by the
fastener manufacturer prior to hot-dip zinc coating (galvanizing).
2. Hot-Dip Zinc Coating:
Effect of Temperature on Mechanical Properties:
Galvanizing carried out at a temperature above 800°F [425°C] can adversely affect the final
mechanical properties of the fasteners. Therefore, the supplier of the fasteners submitting the
product to the galvanizer shall be aware of the tempering temperature of the fasteners relative to
the temperature of the galvanizing bath and the potential effect it may have on the product.When
requested by the purchaser,the average galvanizing temperature that the fasteners will be
subjected to shall be furnished.
Unless otherwise required by the product standard or
by the purchaser, testing for mechanical properties is not necessary if the galvanizing process is
carried out at a lower temperature than the stress relief or tempering temperature of the fasteners.
If the galvanizing process is carried out at a higher temperature than the stress relief or the
tempering temperature of the fasteners, than the purchaser shall make provision for mechanical
testing.
Threaded fasteners made from carbon or alloy steel heat treated to a minimum specified
hardness of 40 HRC, or case hardened steel fasteners shall not be hot-dip zinc coated.
3. Effect of Hydrogen on the Mechanical Properties after Galvanizing—Hydrogen has the potential of
being
introduced into the steel during acid pickling, prior to hot-dip galvanizing. For high strength
fasteners (having a specified minimum product hardness of 33 HRC), there is a risk of internal
hydrogen embrittlement. If required by the product standard or by the purchaser, mechanical descaling
(with or without flash pickling) or baking shall be conducted to reduce the risk of internal hydrogen
embrittlement. Baking shall be conducted after pickling and prior to hot-dip galvanizing.
Effect of the Galvanizing Temperature—Externally threaded ferrous fasteners over 1.00 in. [M24]
diameter with a specified minimum hardness of HRC 33 and higher shall not be hot-dip zinc coated at
high temperature (see definition in 3.1.4) in order to avoid microcracks.
1. Coating Thickness—The zinc coating thickness shall
meet the requirements of below Table. See Supplementary Requirement
S1 when specifying coating thickness for fasteners
meeting the requirements of Specification A394.
2.Dimension—The dimensional characteristics of the fasteners shall be in accordance with the
requirements of the purchaser, when specified in the order. The purchaser shall ensure that the effect
of the heat generated by the galvanizing process is compatible with the fastener regarding the final
dimensional characteristics of the parts. Furthermore, the galvanizer shall not be held responsible
for any unanticipated distortion of parts. In addition, the purchaser shall provide fasteners having
sufficient dimensional allowance to accommodate the zinc thickness deposition, as required in 1.
Adhesion of Zinc Coating—The zinc coating shall adhere tenaciously to the surface of the base metal.
The method for testing the condition of adherence is specified in
| Minimum Thickness on Surface | |||
|---|---|---|---|
| Dimension A, B | Average Thickness of All Specimens Tested (Production Lot) C, B | Average Thickness of All Specimens Tested (Batch Lot) D, B | Average Thickness of Individual Specimen B |
| Fasteners and nuts over 3⁄8 in. [M10] in diameter | 0.0020 in. [50 μm] | 0.0017 in. [43 μm] | 0.0017 in. [43 μm] |
| Washers 3⁄16 in. [4.7 mm] and over in thickness | |||
| Fasteners and nuts 3⁄8 in. [M10] and under in diameter | 0.0017 in. [43 μm] | 0.0015 in. [38 μm] | 0.0015 in. [38 μm] |
| Washers under 3⁄16 in. [4.7 mm] in thickness | |||
A In the case of long pieces, such as anchor rods and similar articles over 5 ft [1.5 m] in
length, the thickness measurement shall be determined at each end and the middle of the article. In the
case of a fully threaded rod, the thickness measurements shall be determined at each end of the article.
In no case shall the average of the measurements be below the average thickness shown in the Average
Thickness on Individual Specimen column (see 11.2). The number of specimens to be tested per order shall
be as specified in Section 10. Note—Based upon mathematical calculations, 1.0 oz /ft2 [305g/m2] of zinc
surface corresponds to an average coating thickness of 0.0017 in. [43 μm].
B Inch-pound and SI units may not be exact equivalents. See 1.3.
C For test method, see 11.2. In no case shall the average reading of a single specimen be
below the
average thickness shown in the Average Thickness on Individual Specimen column.
D See 5.2.1 and Table 1. For test method, see 11.2. In no case shall the average reading of a
single
specimen be below the average thickness shown in the Average Thickness on Individual Specimen column.
Appearance of Zinc Coating:
1. Appearance of Zinc Coating:
After hot-dip galvanizing, the fasteners shall meet the requirements of the section on Workmanship,
Finish, and Appearance of Specification A153/A153M. Galvanized washers shall not be bonded to each other
(See Note 3). Parts may be dull due to the presence of silicon in the steel. The dull
appearance shall not be cause for rejection.
NOTE 3—Hot-dip washers tend to bond to each other. Suitable acceptance
criteria shall be agreed between the purchaser and the galvanizer
before placing the order. Unless otherwise agreed to in the purchase order,
delivered galvanized washers shall not be bonded to each other.
2. The test method shall be in accordance.
Smoothness of Zinc Coating:
1. The zinc coating shall be smooth and reasonably
uniform in thickness, as defined in the section on
Workmanship, Finish, and Appearance of Specification A153/A153M. Smoothness of a surface is a relative term. Minor
roughness that does not impair the intended use of the part, or
roughness that is related to the uncoated surface condition of
the part, shall not constitute grounds for rejection of the parts.
The test method shall be in accordance.
1. Test specimens shall be selected at random from each production lot or batch lot, when
applicable.
2. Selection of the Sampling Plan–Production Lot—Two sampling plans are proposed, one based on detection
process and one based on prevention process as defined in Terminology
F1789.
The selection of the sampling plan shall be in accordance with Guide
F1470.
Production Lot–Detection Process—Sampling for coating thickness and for visual appearance shall be
conducted in accordance with Table 1, Sample Level A, and Table 3, Sample Size A, of Guide
F1470. Sampling for adhesion test shall be in accordance
with Table 1, Sample Level C, and Table 3, Sample Size C, of Guide
F1470.
Production Lot–Prevention Process—Sampling for coating thickness and for visual appearance shall be
conducted in accordance with Table 2, Sample Level B, and Table 3 Sample Size B, of Guide
F1470. Sampling for adhesion test shall be in accordance with Table 2,
Sample Level D, and Table 3, Sample Size D, of Guide F1470.
Tests shall be made to ensure that the zinc coating is being furnished in accordance with this specification and as specified for the following:
Coating Thickness:
1. Average Coating Thickness on an Individual Specimen:
To calculate the average coating thickness of one specimen, a minimum of five readings shall be taken.
In case the geometry of the specimen does not permit five readings, five test specimens shall be used to
establish the average reading.
The determination of the coating thickness shall be made on a portion of the fastener that does not
include any threads in accordance with Practice E376.
In case of arbitration, the thickness of coating shall be determined by cross section and optical
measurement, in accordance with Test Method B487. Thus, the thickness determined is a point value. No
less than five measurements shall be made at locations on the test specimen, which are as widely
dispersed as practical, so as to be representative of the whole surface of the test specimen. The
average of those selected measurements is the average coating thickness.
Finish and Appearance—Finish and appearance shall be visually inspected.
Embrittlement Test—If the product standard requires testing for hydrogen embrittlement of galvanized fasteners, testing shall be done in accordance with Test Methods F606/F606M or other test method(s), as required by the purchaser.
Adhesion Test—Testing for adherence shall be conducted as determined in the section on Adherence of Specification A153/A153M.
When the purchaser requires dimensional inspection of the fasteners by the galvanizer, the purchaser
shall provide the necessary inspection tools and gages to the galvanizer.
The representative of the purchaser shall have access at all times while work on the contract of the
purchaser is being performed, to those areas of the galvanizer’s work which concern the application of
the zinc coating to the fastener ordered. The manufacturer shall afford the representative of the
purchaser all reasonable facilities to satisfy this representative that the zinc coating is being
furnished in accordance with this specification. All inspections and tests shall be made at the
place of manufacture prior to shipments, unless otherwise specified, and shall be conducted so as not to
unnecessarily interfere with the operation of the works.
When partial inspection of fasteners to determine conformity with visual requirements of Section 9
warrants rejection of a lot, the galvanizer may sort the lot and submit it once again for
inspection.
Disposition of nonconforming lots shall be in accordance with the section on Disposition of
Nonconforming Lots
of Guide F1470.
Fasteners that have been rejected for reasons other than embrittlement may be stripped and re-galvanized
and submitted for test and inspection. They shall then conform to the requirements of this
specification.
When specified in the purchase order or contract, certification shall be furnished declaring that samples representing each lot have been either tested or inspected, as required by this specification, and that the requirements have been met. When specified in the purchase order or contract, the average galvanizing temperature shall be reported and the average thickness of the production lot shall be furnished.
When the galvanizer is required to pack hot-dip galvanized fasteners, they shall not be packed in unventilated containers, if fabricated from unseasoned wood. The packaging shall comply with the purchaser requirements.
Coatings, zinc; galvanized coatings; steel zinc coated; steel fastener products, metallic coated; zinc coating fastener products.
The following requirements shall be applied when specified by the purchaser on the inquiry and order.
Details of these requirements shall be agreed upon in writing between the manufacturer and
purchaser.
ASTM A394 Coating Thickness:
When Supplementary Requirement ASTM A394 is specified on the order, the minimum average thickness of
zinc
shall be 0.0028 in. or (70 μm) and the minimum average thickness of any one item shall be 0.0025 in. or
(63 μm).
1. GALVANIZING TEMPERATURE
Normally galvanizing is carried out at a bath temperature of 820°F to 900°F [435°C to 480°C]. High
temperature galvanizing is used to produce a smoother and thinner coating and is carried out at a bath
temperature of 990°F to 1040°F [530°C to 560°C]. The finish obtained using the high temperature
process is dull.
2. VARIATION IN COATING
During galvanizing of a production lot, variation can be experienced due to factors inherent to the
galvanizing process, such as immersion time, zinc temperature, time span between removal of fasteners
from the zinc bath and the centrifuging, and the like.
ASTM Standards:
A153/A153M
Specification for Zinc Coating
(Hot-Dip) on Iron and Steel Hardware.
A394 Specification for Steel Transmission Tower Bolts,
Zinc-Coated and
Bare.
A563 Specification for Carbon and Alloy Steel Nuts.
A563M Specification for Carbon and Alloy Steel Nuts
(Metric).
A780/A780M
Practice for Repair of Damaged and
Uncoated Areas of Hot-Dip Galvanized Coatings.
B487 Test Method for Measurement of Metal and Oxide Coating
Thickness by
Microscopical Examination of Cross Section.
E376 Practice for Measuring Coating Thickness by Magnetic-Field or Eddy-Current (Electromagnetic)
Testing Methods.
F606/F606M Test
Methods for Determining the Mechanical Properties of Externally and Internally Threaded Fasteners,
Washers, Direct Tension Indicators, and Rivets.
F1470 Practice for Fastener Sampling for Specified
Mechanical Properties and Performance Inspection.
F1789 Terminology for F16 Mechanical Fasteners.