ASTM F3044-20

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of the standard as published by ASTM is to be considered the official document.
Designation: F3044 − 14 F3044 − 20
Standard Test Method for
Evaluating the Potential for Galvanic Corrosion for Medical
Implants
This standard is issued under the fixed designation F3044; 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 covers conducting galvanic corrosion tests to characterize the behavior of two dissimilar metals in electrical
contact that are to be used in the human body as medical implants or as component parts to medical implants. Examples of the
types of devices that might be assessed include overlapping stents of different alloys, stent and stent marker combinations,
orthopedic plates and screws where one or more of the screws are of a different alloy than the rest of the device, and multi-part
constructs where two or more alloys are used for the various component parts. Devices which are to be partially implanted, but
in long-term contact within the body (such as external fixation devices) may also be evaluated using this method.
1.2 This test method covers the selection of specimens, specimen preparation, test environment, method of exposure, and method
for evaluating the results to characterize the behavior of galvanic couples in an electrolyte.
1.3 Devices and device components are intended to be tested in their finished condition, as would be implanted (that is, the
metallurgical and surface condition of the sample should be in or as close as possible to the same condition as in the finished
device).
1.4 This test method does not address other types of corrosion and degradation damage that may occur in a device such as fretting,
crevices, or the effect of any galvanically induced potentials on stress corrosion and corrosion fatigue. Surface modifications, such
as from scratches (possibly introduced during implantation) or effects of welding (during manufacture), are also not addressed.
These mechanisms are outside of the scope of this test method.
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.6 Warning—Mercury has been designated by many regulatory agencies as a hazardous substance that can cause serious medical
issues. Mercury, or its vapor, has been demonstrated to be hazardous to health and corrosive to materials. Use caution when
handling mercury and mercury-containing products. See the applicable product Safety Data Sheet (SDS) for additional
information. The potential exists that selling mercury or mercury-containing products, or both, is prohibited by local or national
law. Users must determine legality of sales in their location.
1.7 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.
This test method is under the jurisdiction of ASTM Committee F04 on Medical and Surgical Materials and Devices and is the direct responsibility of Subcommittee
F04.15 on Material Test Methods.
Current edition approved Jan. 15, 2014Aug. 15, 2020. Published May 2014August 2020. Originally approved in 2014. Last previous edition approved in 2014 as
F3044 – 14. DOI: 10.1520/F3044-14.10.1520/F3044-20.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F3044 − 20
NOTE 1—Additional information on galvanic corrosion testing and examples of the conduct and evaluation of galvanic corrosion tests in electrolytes are
given in Ref. given.(1).
1.8 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:
D1193 Specification for Reagent Water
F2129 Test Method for Conducting Cyclic Potentiodynamic Polarization Measurements to Determine the Corrosion Suscepti-
bility of Small Implant Devices
G1 Practice for Preparing, Cleaning, and Evaluating Corrosion Test Specimens
G3 Practice for Conventions Applicable to Electrochemical Measurements in Corrosion Testing
G5 Reference Test Method for Making Potentiodynamic Anodic Polarization Measurements
G15 Terminology Relating to Corrosion and Corrosion Testing (Withdrawn 2010)
G16 Guide for Applying Statistics to Analysis of Corrosion Data
G31 Guide for Laboratory Immersion Corrosion Testing of Metals
G46 Guide for Examination and Evaluation of Pitting Corrosion
G59 Test Method for Conducting Potentiodynamic Polarization Resistance Measurements
G71 Guide for Conducting and Evaluating Galvanic Corrosion Tests in Electrolytes
G82 Guide for Development and Use of a Galvanic Series for Predicting Galvanic Corrosion Performance
G102 Practice for Calculation of Corrosion Rates and Related Information from Electrochemical Measurements
G215 Guide for Electrode Potential Measurement
3. Significance and Use
3.1 Implantable medical devices can be made of dissimilar metals or come into electrical contact with dissimilar metals leading
to the potential for galvanic corrosion, which may result in the release of corrosion products with harmful biological consequences
or a compromise of structural integrity of the device. Therefore, it is important to determine the susceptibility of these types of
devices to galvanic corrosion.
3.2 Use of this test method is intended to provide information on the possible galvanic component of corrosion of two dissimilar
metals in contact with one another. The dissimilar metals in contact may be on the same implantable medical device or as
component parts of individual medical implant devices.
3.3 This test method has been designed to accommodate a wide variety of device shapes and sizes encountered by allowing the
use of a variety of holding devices.
3.4 This standard is presented as a test method for conducting galvanic corrosion tests in a simulated physiological environment.
Adherence to this test method should aid in avoiding some of the inherent difficulties in such testing. Other standards such as Guide
G71 are general and, while they provide valuable background information, do not provide the necessary details or specificity for
testing medical device implants.
4. Apparatus
4.1 Potentiostat, verified in accordance with Reference Test Method G5. Other means of verifying the accuracy and reliability of
the potentiostat may be used, so long as this is adequately documented. For this test method, the potentiostat should be a high
impedance instrument configured as a zero resistance ammeter (ZRA). Alternatively, a setup consisting of a dedicated ZRA, an
electrometer and a two-channel recorder for recording the galvanic current and galvanic potential with time can be used. The
currents measured during the test are likely in the nA range (or lower). The instrument used should be capable of reliably measuring
such currents.
The boldface number in parentheses refers to the reference provided at the end of the document.Marek, M., “Corrosion Testing of Implantable Medical Devices,”
Handbook of Materials for Medical Devices, Vol 23, ASM International, 2012.
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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4.2 The Tested Samples, prepared as individual electrodes of the galvanic couple. The configuration of each electrode and holder
will depend on the type of specimen being tested, as described in 5.2. The sample holder can be of various configurations, provided
it allows for good electrical connection to the sample, provides a method of electrical connection outside of the test cell, ensures
that the sample sits fully below the liquid level line in the test cell, does not come into physical contact with any other element
of the cell or apparatus, and allows for masking of the sample at the point of connection.
4.3 Reference Electrode—A standard reference electrode should be used in the test. Examples of standard electrodes are provided
in Guide G215a verified , along with a table showing conversions between electrodes. The reference electrode used in the test shall
be identified along with the conversion used, if necessary. Individual electrochemical potentials such as E and E should be
b r
reported relative to the saturated calomel electrode (SCE), as described in Reference Test Method (SCE). (For example, G5, is the
preferred reference electrode. If another standard electrode is used (for example, Ag/AgCl), data should be adjusted so that it is
reported with respect to SCE.the saturated Ag/AgCl electrode is 45 mV electronegative to SCE. A reading of 0 mV versus Sat’d.
Ag/AgCl would be equivalent to a reading of –45 mV versus SCE. Therefore, to convert potentials measured using a Sat’d.
Ag/AgCl electrode to the SCE scale, 45 mV should be subtracted.) When plotting curves, potentials may be plotted using raw data,
that is, to the scale of the reference electrode used during the test and this shall be clearly shown on the axis label (for example,
“Potential versus SCE (mV)” or “Potential versus Sat’d. Ag/AgCl (mV)”).
NOTE 2—Due to the presence of mercury in the saturated calomel electrode (SCE) and the increasing regulation around the use of equipment and materials
that contain mercury, there may be decreased availability of SCE as a reference electrode. When choosing a reference electrode for testing, users of this
standard should also take note of any regulations relevant to their region.
4.4 Salt Bridge, such as a Luggin probe, may be used between the working and reference electrode, such as the type shown in
Reference Test Method G5.
4.5 Suitable Polarization Cell, with a volume of at least 500 cm500 cm , equivalent to or similar to that recommended in
Reference Test Method G5. The volume of the cell may be greater than 500 cm500 cm if needed to accommodate a larger sample.
4.6 Water Bath, or other heating appliance capable of maintaining the test solution temperature at 37 6 1°C. Note that use of a
hot plate to heat and/or agitate the solution (for example, using a magnetic stir bar) can cause excessive noise and interfere with
the electrochemical data.
4.7 Gas Bubbler, to provide aeration and agitation, capable of delivering aeration at a rate of 150 cm150 cm /min.
4.8 Thermometer, with an accuracy for measurement within 61°C.
4.9 pH meter, with an accuracy for measurement within 60.1.
4.10 An example of a typical test cell set-up is provided in Fig. X2.1Fig. X2.1.
5. Test Specimens
5.1 Material—Unless otherwise justified, all samples selected for testing should be taken from finished product that has been
subjected to all normal manufacturing processes and is considered acceptable for clinical use. Cosmetic rejects or other nonclinical
samples may be used if the cause for rejection would not affect the galvanic corrosion behavior of the device, but the metallurgical
and surface condition of the sample should be in or as close as possible to the same condition as the finished device. Sterilization
or other manufacturing processes may be omitted if it can be demonstrated that these processes have no effect on the galvanic
corrosion behavior of the device.
NOTE 3—Loading or deployment of samples, as it would occur in vivo, should be simulated as closely as is reasonably possible, since these actions can
potentially affect the overall corrosion behavior of the material. Because anode and cathode must be separated for testing, it is understood that this step
may not be possible.
5.2 Selection of Anode and Cathode:
F3044 − 20
5.2.1 It is preferable to evaluate the components before the test is initiated to determine which one would likely be the anode and
which would be the cathode. For example, in a device containing two alloys, such as a stent with markers, one material will be
the anode and the other will be the cathode.
5.2.2 Published galvanic series are available to help with the determination of anode/cathode (see Guide G82, for instance.)
However, it should be remembered that these series are published for specific electrolytes, which may or may not accurately
represent the test electrolyte or in vivo conditions. Alternatively, the open circuit potential (OCP) can be measured for each material
in the chosen electrolyte, in order to establish their relative positions electrochemically. The material with the less noble value of
the OCP will likely be the anode.
NOTE 4—Open circuit potential, for the purpose of determining anodic or cathodic condition, should be measured after a minimum of 1 h in contact with
the solution. The samples used for this measurement should not then be used in the galvanic test.
5.2.3 Where a choice exists as to the relative sizes of the anode and cathode (for example, if the device comes in several sizes
and the anode-to-cathode surface area ratio is different for different sizes), it should be remembered that the most aggressive
galvanic couple occurs with a smaller anode relative to a larger cathode.
5.2.4 In the case where three or more alloys are to be tested for their galvanic corrosion behavior, the single most active component
(anode) should be tested against a combination of the other components. If more than one component of a multi-component device
is suspected of being prone to galvanic corrosion, each can be tested against the rest of the components joined together. Joining
requires mounting components together in electrical contact with one another, as a single electrode (or electrode bundle). This may
be accomplished by joining the electrical connections to the components outside the cell or by joining components that are to be
exposed together inside the cell. The latter may require spot welding or other techniques. It is important to mask off any areas that
are spot welded or otherwise altered from their original form during connection and mounting, so that these areas do not become
part of the test. Materials suitable for use in masking should be impermeable to water and capable of isolating the area masked
off, without contributing unwanted crevice effects.
5.2.5 The anode and cathode should be separated for testing. In some devices, particularly those containing complex, multi-alloy
component parts that may be fused or brazed together, separation of anode and cathode may be difficult or impossible. In these
cases, it is acceptable to mask off various areas of the part, leaving only the desired material(s) exposed.
5.2.6 Where possible, as much of the device as possible should be tested while maintaining the ratio of surface areas between
anode and cathode. It is understood that small area(s) of the device will likely be masked off due to fixturing requirements.
5.3 Surface Area Calculation:
5.3.1 The relative surface area ratio of anode material to cathode material in the test samples should be maintained (that is, mimic
the actual device) during the test. A worst case ratio may be used, but this should be based on a ratio that can actually occur in
the device based on device tolerances, size variations, or differences in intended usage (see 5.2.3). An artificial worst case (for
example, choosing a ratio that does not occur or is artificially high), is not recommended.
5.3.2 The surface area of the entire anode and entire cathode should be calculated from drawings or measurements. The area where
the material is connected to the testing apparatus, which is masked, should be subtracted. In the case of stents containing multiple
markers, the total exposed surface area of the markers should be used.
5.3.2.1 Ideally, decoupling the anode and cathode can be accomplished such that entire sub-component parts may be tested. In this
case, the surface area ratio of anode to cathode should naturally be preserved. In some cases, however, it may not be practicable
to decouple the materials of interest while preserving the components. In these cases, a test specimen may be used to simulate the
total area of the material of interest. For example, if a stent with multiple markers is to be tested, a single piece of the marker
material (such as a strip, tube, or sheet that is in as close as possible to the same metallurgical condition as the markers themselves)
with area equal to the total surface area of the exposed marker material in the device may be tested against a single bare stent with
markers removed or masked.
5.4 Number of Specimens: Specimens—As a minimum, duplicate and preferably triplicate specimens should be tested to determine
the variability in the galvanic corrosion behavior. The effect of the number of replications on the application of the results is set
forth in Guide G16.
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6. Test Environment
6.1 The test solution should be chosen to approximate the intended in vivo environment.
6.2 Reagent grade chemicals should be used for this test method. Such reagents should conform to the specifications of the
Committee on Analytical Reagents of the American Chemical Society.
6.3 The water should be distilled or deionized (DI) and should conform to the purity requirements of Specification D1193, Type
IV reagent water.
6.4 Unless otherwise specified, phosphate buffered saline (PBS) should be used as the standard test solution. A variety of simulated
physiological solutions are listed in Test Method F2129, Appendix X2.
6.5 The pH of the electrolyte should be adjusted if necessary based on the nature of the solution by the addition of Na HPO (base)
2 4
or NaH PO (acid), as needed. Several pH controlling methods are provided in Appendix X2 of Test Method F2129.
2 4
6.6 The test should be conducted in an aerated environment (for example, using forced bubbling of laboratory air).
7. Procedure
NOTE 5—Specimens should be handled carefully so as not to contaminate or alter them. For examples, gloves should be worn to protect samples from
contamination from oils from your hands.
7.1 Examine the samples in the stereomicroscope, as received, in order to assess their condition prior to testing. The purpose of
the microscopy is to document the general characteristics of the device, but not to fully characterize it.
7.2 Select the anode and cathode in accordance with 5.2. Mount the test samples on suitable holders and mask off the connection
points. Samples should be fully immersed for testing. Any portion of the sample not immersed or any conductive part of the
mounting apparatus should be masked off to minimize unwanted effects.
7.3 Calculate separately the total surface area of the anode and of the cathode exposed to the solution in
...