ASTM F2660-20

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Designation: F2660 − 13 F2660 − 20
Standard Test Method for
Qualifying Coatings for Use on F3125 Grade A490 Structural
Bolts Relative to Environmental Hydrogen Embrittlement
This standard is issued under the fixed designation F2660; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This test method defines the procedures and tests to evaluate the effect of a coating system on the susceptibility to
environmental hydrogen embrittlement (EHE) of an ASTM A490F3125 Grade A490 high strength structural bolt.
1 1
1.2 This test method shall qualify a coating system for use with any size of A490F3125 Grade A490 bolts (that is, ⁄2 to 1- ⁄2
in.) high strength structural bolts, relative to EHE.
1.3 The characteristic to be evaluated by this test method is the susceptibility to EHE caused by hydrogen generated from
corrosion protection of the steel bolt by sacrificial galvanic corrosion of the coating. Testing shall be performed on coated,
specimen ASTM A490F3125 Grade A490 bolts manufactured to the maximum susceptible tensile strength values (see Table 1)
of the bolt (see Section 5 Specimen Bolt Requirements). The internal hydrogen embrittlement (IHE) susceptibility will also be
inherently evaluated when the EHE is tested through this test method. There is no need for a separate IHE susceptibility test.
1.4 The values stated in inch-pound units are to be regarded as standard. No other units of measurement are included in this
standard.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
A490 Specification for Structural Bolts, Alloy Steel, Heat Treated, 150 ksi Minimum Tensile Strength (Withdrawn 2016)
E4 Practices for Force Verification of Testing Machines
E8/E8M Test Methods for Tension Testing of Metallic Materials
F519 Test Method for Mechanical Hydrogen Embrittlement Evaluation of Plating/Coating Processes and Service Environments
F606F606/F606M Test Methods for Determining the Mechanical Properties of Externally and Internally Threaded Fasteners,
Washers, and Rivets (Metric) F0606_F0606M Direct Tension Indicators, and Rivets
F1624 Test Method for Measurement of Hydrogen Embrittlement Threshold in Steel by the Incremental Step Loading Technique
F1789 Terminology for F16 Mechanical Fasteners
F2078 Terminology Relating to Hydrogen Embrittlement Testing
F3125 Specification for High Strength Structural Bolts and Assemblies, Steel and Alloy Steel, Heat Treated, Inch Dimensions
120 ksi and 150 ksi Minimum Tensile Strength, and Metric Dimensions 830 MPa and 1040 MPa Minimum Tensile Strength
G3 Practice for Conventions Applicable to Electrochemical Measurements in Corrosion Testing
G15 Terminology Relating to Corrosion and Corrosion Testing (Withdrawn 2010)
G44 Practice for Exposure of Metals and Alloys by Alternate Immersion in Neutral 3.5 % Sodium Chloride Solution
G82 Guide for Development and Use of a Galvanic Series for Predicting Galvanic Corrosion Performance
This test method is under the jurisdiction of ASTM Committee F16 on Fasteners and is the direct responsibility of Subcommittee F16.01 on Test Methods.
Current edition approved Nov. 1, 2013April 1, 2020. Published December 2013April 2020. Originally approved in 2012 2012. Last previous edition approved in 2013
as F2660–12.–13. DOI: 10.1520/F2660–13.10.1520/F2660–20.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
The last approved version of this historical standard is referenced on www.astm.org.
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F2660 − 20
TABLE 1 Specimen Bolt Sizes and Wedge Tensile Load Values
Tensile
Nominal Minimum Wedge Tensile
Stress
Size Length Load
Area
As Min. Max.
(D) (in.)
(in. ) (lb) (lb)
1/2-13 1-1/2 0.1419 25,600 27,600
3/4-10 2-1/2 0.3345 59,000 63,000
1-8 5 0.6057 103,000 107,000
2.2 Research Council on Structural Connections:
Specification for Structural Joints Using High Strength Bolts (LRFD) Load and Resistance Factor Design
Specification for Structural Joints Using High Strength Bolts (ASD) Allowable Stress Design
2.3 Other References:
Townsend Jr., H. E., Met Trans, V6A, April, 1976
Raymond, L., The Susceptibility of Fasteners to Hydrogen Embrittlement and Stress Corrosion Cracking: Fastener System
Design. In J. H. Bickford, & S. Nassar, Handbook of Bolts and Bolted Joints, New York, USA: Marcel Dekker, Inc., 1998,
pp. 723-756
2.4 International Standards Organization (ISO):
ISO 17025 General Requirements for the Competence of Testing and Calibration Laboratories
3. Terminology
3.1 Definitions:
3.1.1 Terminology for this test method shall be used in accordance with Terminology F1789, Terminology F2078, and
Terminology G15 except as described below.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 specimen lot, n—at least 100 ASTM A490F3125 Grade A490 specimen bolts manufactured in the same process from the
same lot of a steel alloy.
3.2.2 specimen bolt, n—is a bolt with dimensions that conform to the requirements of A490A490 bolt dimensions but has
mechanical properties, which exceed those of A490ASTM F3125 Grade A490 requirements (see 5.1.1 and Table 1).
4. Significance and Use
4.1 This test method describes the testing procedure that shall be used to qualify a coating system that is under consideration
for use on ASTM A490F3125 Grade A490 high strength structural bolts made of any steel composition permitted by the
A490F3125 specification. specification for Grade A490 bolts. The test method measures the susceptibility of coated specimen bolts
to the influence of an externally applied potential (see 7.2.3.3) by testing for the threshold of embrittlement in a salt solution
environment.
5. Specimen Bolt Requirements
5.1 Coated Bolts:
5.1.1 Testing shall be carried out using specially processed ASTM A490F3125, Grade A490, Type 1 specimen bolts specially
heat treated to achieve maximum strength values per Table 1 in order to qualify the Standard A490F3125 Grade A490 bolts.
Specimen bolts are designed to simulate a worst case material condition with respect to susceptibility to environmental hydrogen
embrittlement (EHE). For this reason, wedge tensile values for specimen bolts exceed the maximum limits for A490F3125 Grade
A490 bolts; therefore, the specimen bolts shall not have standard A490F3125 Grade A490 markings so they will not be identified
as standard A490F3125 Grade A490 bolts.
5.1.2 Specimen bolts shall be one of two nominal inch sizes: 3/4-10 UNC or 1-8 UNC. Alternatively, small specimen size bolts,
1/2-13 UNC may be used, but are subject to more severe strength requirements shown in 8.4.
5.1.3 Specimen bolts shall for a lot that displays the maximum wedge tensile load condition permitted by Specification
A490F3125, when tested in accordance with Test Methods F606F606/F606M Grade A490. Table 1 gives the range of acceptable
wedge tensile loads for each specimen bolt size.
5.1.4 Test results shall be provided by an ISO 17025 accredited laboratory. Wedge tensile strengths for the specimen bolts must
be within the range specified in Table 1 and dimensional and compositional conformance to Specification A490F3125 Grade A490
shall be provided by the supplier of each specimen lot.
5.2 Coatings:
5.2.1 The coating to be evaluated shall be applied to all specimen bolts under normal production conditions.
5.2.2 The process of coating specimen bolts shall include all post-coating processing under normal production conditions.
F2660 − 20
5.3 Uncoated Bolts:
5.3.1 Testing shall be carried out using ASTM A490A490 Type 1 bolts produced at the same time with the same processes and
from the same lot of steel alloy as coated bolts.
6. Sample Quantities Required
6.1 A minimum of fifteen (15) bolts from any specimen lot shall be used for evaluation and qualification. Ten (10) bolts shall
be coated and the remaining five (5) bolts shall remain uncoated. Additional samples may be required for repeat test and shall be
held in contingency.
7. Test Procedures
7.1 Open Circuit Potential (OCP):
7.1.1 The freely corroding or Open Circuit Potential (OCP) shall be measured in 3.5%3.5 % NaCl solution produced in
accordance with Practice G44 to characterize the galvanic corrosion behavior of the coating relative to the steel bolt. The OCP
measurement shall be made on a coated specimen bolt in accordance with Practice G3. The OCP measurement shall be taken using
a potentiostat capable of making measurements with a resolution no less than 6 5 mV.
NOTE 1—If the coating is a known material then the measured OCP can be compared to the values described in Guide G82.
7.1.2 A second OCP test shall be performed and the two tests shall be compared for consistency. If the OCP test is not 6 5 mV
with a known value for a known coating or with the other OCP test for an unknown coating, then a known material other than the
coating shall be used to test the accuracy of the reference electrode. If the electrode is accurate, then another bolt sample shall be
tested to obtain consistency. Some reasons for inconsistency include dissimilar materials in the test setup or coating voids that can
change the OCP value.
7.2 Environmental Hydrogen Embrittlement Testing:
7.2.1 Mechanical Test Set-up:
7.2.1.1 The test shall be conducted on bolts that have been truncated by removal of the bolt head. Cut off the bolt head using
a water cooled cut off saw or other device that does not cause excessive heating of the bolt. The length of the specimen bolt for
testing shall be a minimum length of 1.5 inchesin. and a maximum length of 4.0 inches.in. The truncated bolt specimen shall be
adjusted to achieve the placement of a minimum of two threads between the gripping devices. The exposed threads shall be equally
spaced on each side of the minor diameter of the threads. This placement of the bolt specimen in the gripping device is shown in
Fig. 1.
7.2.1.2 The loading method required for this test is four-point (4 pt) bend, which produces constant moment along the gage
section so that the stress may be calculated anywhere along the length of the fastener. The test is conducted under displacement
control. The loading method shall have a specified load accuracy of 6 0.5%,0.5 %, programmable to increase incrementally in
steps of load and time. The loading method shall be within the guidelines of calibration, force range, resolution, and verification
of Practices E4.
7.2.2 Fast Fracture Testing:
7.2.2.1 The first step in the testing sequence shall be a measurement of the fast fracture load of the specimen bolts in bending.
Determine this value by performing a test in accordance with Test Method F1624, Section 8, as shown in Fig. 2A, using a fast
FIG. 1 Four-Point Bend Loading of Fasteners. Maximum Tensile Stress, σ = 32P λ/Πd
t b
F2660 − 20
FIG. 2 Fast Fracture Testing and Step Loading Profile
fracture protocol. Test a minimum of five uncoated specimen bolts and a minimum of five coated specimen bolts. The average of
these five test results shall determine the fast fracture strength of each condition.
7.2.2.2 The average fast fracture strength in bending of coated bolts, FFS(B) must be within 6 5%5 % of the average fast
coated
fracture strength for uncoated bolts, FFS(B) . If the coated bolts exhibit a fast fracture strength that is below 95% of the fast
uncoated
fracture strength for uncoated bolts, the coating is disqualified from this test.
NOTE 2—Lower than 95% fast fracture strength for the coated samples is an indication that the coating process may have affected the strength of the
specimen bolts.
7.2.3 EHE Sample Testing:
7.2.3.1 To measure the EHE susceptibility of the fastener/coating system, bolts are tested in the environment/setup described
in section 7.1.1 and 7.2.3.3 using the step load methodology described in Test Method F1624, Section 8, to measure P .
th
7.2.3.2 A galvanic condition (see Annex A1) is created by inscribing a mark in the coating at the root of a bolt thread to expose
the steel substrate. This condition simulates a damaged coating, also referred to as “coating holiday.” The scribe mark in the coating
shall be located between the exposed threads (see Fig. 1) between the gripping devices and shall have a length of at least one
diameter and a width that exposes the thread root. Care must be t
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